xref: /OK3568_Linux_fs/kernel/drivers/media/i2c/ov7670.c (revision 4882a59341e53eb6f0b4789bf948001014eff981)

// SPDX-License-Identifier: GPL-2.0-only
/*
 * A V4L2 driver for OmniVision OV7670 cameras.
 *
 * Copyright 2006 One Laptop Per Child Association, Inc.  Written
 * by Jonathan Corbet with substantial inspiration from Mark
 * McClelland's ovcamchip code.
 *
 * Copyright 2006-7 Jonathan Corbet <corbet@lwn.net>
 */
#include <linux/clk.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/videodev2.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <media/v4l2-device.h>
#include <media/v4l2-event.h>
#include <media/v4l2-ctrls.h>
#include <media/v4l2-fwnode.h>
#include <media/v4l2-mediabus.h>
#include <media/v4l2-image-sizes.h>
#include <media/i2c/ov7670.h>

MODULE_AUTHOR("Jonathan Corbet <corbet@lwn.net>");
MODULE_DESCRIPTION("A low-level driver for OmniVision ov7670 sensors");
MODULE_LICENSE("GPL");

static bool debug;
module_param(debug, bool, 0644);
MODULE_PARM_DESC(debug, "Debug level (0-1)");

/*
 * The 7670 sits on i2c with ID 0x42
 */
#define OV7670_I2C_ADDR 0x42

#define PLL_FACTOR	4

/* Registers */
#define REG_GAIN	0x00	/* Gain lower 8 bits (rest in vref) */
#define REG_BLUE	0x01	/* blue gain */
#define REG_RED		0x02	/* red gain */
#define REG_VREF	0x03	/* Pieces of GAIN, VSTART, VSTOP */
#define REG_COM1	0x04	/* Control 1 */
#define  COM1_CCIR656	  0x40  /* CCIR656 enable */
#define REG_BAVE	0x05	/* U/B Average level */
#define REG_GbAVE	0x06	/* Y/Gb Average level */
#define REG_AECHH	0x07	/* AEC MS 5 bits */
#define REG_RAVE	0x08	/* V/R Average level */
#define REG_COM2	0x09	/* Control 2 */
#define  COM2_SSLEEP	  0x10	/* Soft sleep mode */
#define REG_PID		0x0a	/* Product ID MSB */
#define REG_VER		0x0b	/* Product ID LSB */
#define REG_COM3	0x0c	/* Control 3 */
#define  COM3_SWAP	  0x40	  /* Byte swap */
#define  COM3_SCALEEN	  0x08	  /* Enable scaling */
#define  COM3_DCWEN	  0x04	  /* Enable downsamp/crop/window */
#define REG_COM4	0x0d	/* Control 4 */
#define REG_COM5	0x0e	/* All "reserved" */
#define REG_COM6	0x0f	/* Control 6 */
#define REG_AECH	0x10	/* More bits of AEC value */
#define REG_CLKRC	0x11	/* Clocl control */
#define   CLK_EXT	  0x40	  /* Use external clock directly */
#define   CLK_SCALE	  0x3f	  /* Mask for internal clock scale */
#define REG_COM7	0x12	/* Control 7 */
#define   COM7_RESET	  0x80	  /* Register reset */
#define   COM7_FMT_MASK	  0x38
#define   COM7_FMT_VGA	  0x00
#define	  COM7_FMT_CIF	  0x20	  /* CIF format */
#define   COM7_FMT_QVGA	  0x10	  /* QVGA format */
#define   COM7_FMT_QCIF	  0x08	  /* QCIF format */
#define	  COM7_RGB	  0x04	  /* bits 0 and 2 - RGB format */
#define	  COM7_YUV	  0x00	  /* YUV */
#define	  COM7_BAYER	  0x01	  /* Bayer format */
#define	  COM7_PBAYER	  0x05	  /* "Processed bayer" */
#define REG_COM8	0x13	/* Control 8 */
#define   COM8_FASTAEC	  0x80	  /* Enable fast AGC/AEC */
#define   COM8_AECSTEP	  0x40	  /* Unlimited AEC step size */
#define   COM8_BFILT	  0x20	  /* Band filter enable */
#define   COM8_AGC	  0x04	  /* Auto gain enable */
#define   COM8_AWB	  0x02	  /* White balance enable */
#define   COM8_AEC	  0x01	  /* Auto exposure enable */
#define REG_COM9	0x14	/* Control 9  - gain ceiling */
#define REG_COM10	0x15	/* Control 10 */
#define   COM10_HSYNC	  0x40	  /* HSYNC instead of HREF */
#define   COM10_PCLK_HB	  0x20	  /* Suppress PCLK on horiz blank */
#define   COM10_HREF_REV  0x08	  /* Reverse HREF */
#define   COM10_VS_LEAD	  0x04	  /* VSYNC on clock leading edge */
#define   COM10_VS_NEG	  0x02	  /* VSYNC negative */
#define   COM10_HS_NEG	  0x01	  /* HSYNC negative */
#define REG_HSTART	0x17	/* Horiz start high bits */
#define REG_HSTOP	0x18	/* Horiz stop high bits */
#define REG_VSTART	0x19	/* Vert start high bits */
#define REG_VSTOP	0x1a	/* Vert stop high bits */
#define REG_PSHFT	0x1b	/* Pixel delay after HREF */
#define REG_MIDH	0x1c	/* Manuf. ID high */
#define REG_MIDL	0x1d	/* Manuf. ID low */
#define REG_MVFP	0x1e	/* Mirror / vflip */
#define   MVFP_MIRROR	  0x20	  /* Mirror image */
#define   MVFP_FLIP	  0x10	  /* Vertical flip */

#define REG_AEW		0x24	/* AGC upper limit */
#define REG_AEB		0x25	/* AGC lower limit */
#define REG_VPT		0x26	/* AGC/AEC fast mode op region */
#define REG_HSYST	0x30	/* HSYNC rising edge delay */
#define REG_HSYEN	0x31	/* HSYNC falling edge delay */
#define REG_HREF	0x32	/* HREF pieces */
#define REG_TSLB	0x3a	/* lots of stuff */
#define   TSLB_YLAST	  0x04	  /* UYVY or VYUY - see com13 */
#define REG_COM11	0x3b	/* Control 11 */
#define   COM11_NIGHT	  0x80	  /* NIght mode enable */
#define   COM11_NMFR	  0x60	  /* Two bit NM frame rate */
#define   COM11_HZAUTO	  0x10	  /* Auto detect 50/60 Hz */
#define	  COM11_50HZ	  0x08	  /* Manual 50Hz select */
#define   COM11_EXP	  0x02
#define REG_COM12	0x3c	/* Control 12 */
#define   COM12_HREF	  0x80	  /* HREF always */
#define REG_COM13	0x3d	/* Control 13 */
#define   COM13_GAMMA	  0x80	  /* Gamma enable */
#define	  COM13_UVSAT	  0x40	  /* UV saturation auto adjustment */
#define   COM13_UVSWAP	  0x01	  /* V before U - w/TSLB */
#define REG_COM14	0x3e	/* Control 14 */
#define   COM14_DCWEN	  0x10	  /* DCW/PCLK-scale enable */
#define REG_EDGE	0x3f	/* Edge enhancement factor */
#define REG_COM15	0x40	/* Control 15 */
#define   COM15_R10F0	  0x00	  /* Data range 10 to F0 */
#define	  COM15_R01FE	  0x80	  /*            01 to FE */
#define   COM15_R00FF	  0xc0	  /*            00 to FF */
#define   COM15_RGB565	  0x10	  /* RGB565 output */
#define   COM15_RGB555	  0x30	  /* RGB555 output */
#define REG_COM16	0x41	/* Control 16 */
#define   COM16_AWBGAIN   0x08	  /* AWB gain enable */
#define REG_COM17	0x42	/* Control 17 */
#define   COM17_AECWIN	  0xc0	  /* AEC window - must match COM4 */
#define   COM17_CBAR	  0x08	  /* DSP Color bar */

/*
 * This matrix defines how the colors are generated, must be
 * tweaked to adjust hue and saturation.
 *
 * Order: v-red, v-green, v-blue, u-red, u-green, u-blue
 *
 * They are nine-bit signed quantities, with the sign bit
 * stored in 0x58.  Sign for v-red is bit 0, and up from there.
 */
#define	REG_CMATRIX_BASE 0x4f
#define   CMATRIX_LEN 6
#define REG_CMATRIX_SIGN 0x58


#define REG_BRIGHT	0x55	/* Brightness */
#define REG_CONTRAS	0x56	/* Contrast control */

#define REG_GFIX	0x69	/* Fix gain control */

#define REG_DBLV	0x6b	/* PLL control an debugging */
#define   DBLV_BYPASS	  0x0a	  /* Bypass PLL */
#define   DBLV_X4	  0x4a	  /* clock x4 */
#define   DBLV_X6	  0x8a	  /* clock x6 */
#define   DBLV_X8	  0xca	  /* clock x8 */

#define REG_SCALING_XSC	0x70	/* Test pattern and horizontal scale factor */
#define   TEST_PATTTERN_0 0x80
#define REG_SCALING_YSC	0x71	/* Test pattern and vertical scale factor */
#define   TEST_PATTTERN_1 0x80

#define REG_REG76	0x76	/* OV's name */
#define   R76_BLKPCOR	  0x80	  /* Black pixel correction enable */
#define   R76_WHTPCOR	  0x40	  /* White pixel correction enable */

#define REG_RGB444	0x8c	/* RGB 444 control */
#define   R444_ENABLE	  0x02	  /* Turn on RGB444, overrides 5x5 */
#define   R444_RGBX	  0x01	  /* Empty nibble at end */

#define REG_HAECC1	0x9f	/* Hist AEC/AGC control 1 */
#define REG_HAECC2	0xa0	/* Hist AEC/AGC control 2 */

#define REG_BD50MAX	0xa5	/* 50hz banding step limit */
#define REG_HAECC3	0xa6	/* Hist AEC/AGC control 3 */
#define REG_HAECC4	0xa7	/* Hist AEC/AGC control 4 */
#define REG_HAECC5	0xa8	/* Hist AEC/AGC control 5 */
#define REG_HAECC6	0xa9	/* Hist AEC/AGC control 6 */
#define REG_HAECC7	0xaa	/* Hist AEC/AGC control 7 */
#define REG_BD60MAX	0xab	/* 60hz banding step limit */

enum ov7670_model {
	MODEL_OV7670 = 0,
	MODEL_OV7675,
};

struct ov7670_win_size {
	int	width;
	int	height;
	unsigned char com7_bit;
	int	hstart;		/* Start/stop values for the camera.  Note */
	int	hstop;		/* that they do not always make complete */
	int	vstart;		/* sense to humans, but evidently the sensor */
	int	vstop;		/* will do the right thing... */
	struct regval_list *regs; /* Regs to tweak */
};

struct ov7670_devtype {
	/* formats supported for each model */
	struct ov7670_win_size *win_sizes;
	unsigned int n_win_sizes;
	/* callbacks for frame rate control */
	int (*set_framerate)(struct v4l2_subdev *, struct v4l2_fract *);
	void (*get_framerate)(struct v4l2_subdev *, struct v4l2_fract *);
};

/*
 * Information we maintain about a known sensor.
 */
struct ov7670_format_struct;  /* coming later */
struct ov7670_info {
	struct v4l2_subdev sd;
#if defined(CONFIG_MEDIA_CONTROLLER)
	struct media_pad pad;
#endif
	struct v4l2_ctrl_handler hdl;
	struct {
		/* gain cluster */
		struct v4l2_ctrl *auto_gain;
		struct v4l2_ctrl *gain;
	};
	struct {
		/* exposure cluster */
		struct v4l2_ctrl *auto_exposure;
		struct v4l2_ctrl *exposure;
	};
	struct {
		/* saturation/hue cluster */
		struct v4l2_ctrl *saturation;
		struct v4l2_ctrl *hue;
	};
	struct v4l2_mbus_framefmt format;
	struct ov7670_format_struct *fmt;  /* Current format */
	struct ov7670_win_size *wsize;
	struct clk *clk;
	int on;
	struct gpio_desc *resetb_gpio;
	struct gpio_desc *pwdn_gpio;
	unsigned int mbus_config;	/* Media bus configuration flags */
	int min_width;			/* Filter out smaller sizes */
	int min_height;			/* Filter out smaller sizes */
	int clock_speed;		/* External clock speed (MHz) */
	u8 clkrc;			/* Clock divider value */
	bool use_smbus;			/* Use smbus I/O instead of I2C */
	bool pll_bypass;
	bool pclk_hb_disable;
	const struct ov7670_devtype *devtype; /* Device specifics */
};

static inline struct ov7670_info *to_state(struct v4l2_subdev *sd)
{
	return container_of(sd, struct ov7670_info, sd);
}

static inline struct v4l2_subdev *to_sd(struct v4l2_ctrl *ctrl)
{
	return &container_of(ctrl->handler, struct ov7670_info, hdl)->sd;
}



/*
 * The default register settings, as obtained from OmniVision.  There
 * is really no making sense of most of these - lots of "reserved" values
 * and such.
 *
 * These settings give VGA YUYV.
 */

struct regval_list {
	unsigned char reg_num;
	unsigned char value;
};

static struct regval_list ov7670_default_regs[] = {
	{ REG_COM7, COM7_RESET },
/*
 * Clock scale: 3 = 15fps
 *              2 = 20fps
 *              1 = 30fps
 */
	{ REG_CLKRC, 0x1 },	/* OV: clock scale (30 fps) */
	{ REG_TSLB,  0x04 },	/* OV */
	{ REG_COM7, 0 },	/* VGA */
	/*
	 * Set the hardware window.  These values from OV don't entirely
	 * make sense - hstop is less than hstart.  But they work...
	 */
	{ REG_HSTART, 0x13 },	{ REG_HSTOP, 0x01 },
	{ REG_HREF, 0xb6 },	{ REG_VSTART, 0x02 },
	{ REG_VSTOP, 0x7a },	{ REG_VREF, 0x0a },

	{ REG_COM3, 0 },	{ REG_COM14, 0 },
	/* Mystery scaling numbers */
	{ REG_SCALING_XSC, 0x3a },
	{ REG_SCALING_YSC, 0x35 },
	{ 0x72, 0x11 },		{ 0x73, 0xf0 },
	{ 0xa2, 0x02 },		{ REG_COM10, 0x0 },

	/* Gamma curve values */
	{ 0x7a, 0x20 },		{ 0x7b, 0x10 },
	{ 0x7c, 0x1e },		{ 0x7d, 0x35 },
	{ 0x7e, 0x5a },		{ 0x7f, 0x69 },
	{ 0x80, 0x76 },		{ 0x81, 0x80 },
	{ 0x82, 0x88 },		{ 0x83, 0x8f },
	{ 0x84, 0x96 },		{ 0x85, 0xa3 },
	{ 0x86, 0xaf },		{ 0x87, 0xc4 },
	{ 0x88, 0xd7 },		{ 0x89, 0xe8 },

	/* AGC and AEC parameters.  Note we start by disabling those features,
	   then turn them only after tweaking the values. */
	{ REG_COM8, COM8_FASTAEC | COM8_AECSTEP | COM8_BFILT },
	{ REG_GAIN, 0 },	{ REG_AECH, 0 },
	{ REG_COM4, 0x40 }, /* magic reserved bit */
	{ REG_COM9, 0x18 }, /* 4x gain + magic rsvd bit */
	{ REG_BD50MAX, 0x05 },	{ REG_BD60MAX, 0x07 },
	{ REG_AEW, 0x95 },	{ REG_AEB, 0x33 },
	{ REG_VPT, 0xe3 },	{ REG_HAECC1, 0x78 },
	{ REG_HAECC2, 0x68 },	{ 0xa1, 0x03 }, /* magic */
	{ REG_HAECC3, 0xd8 },	{ REG_HAECC4, 0xd8 },
	{ REG_HAECC5, 0xf0 },	{ REG_HAECC6, 0x90 },
	{ REG_HAECC7, 0x94 },
	{ REG_COM8, COM8_FASTAEC|COM8_AECSTEP|COM8_BFILT|COM8_AGC|COM8_AEC },

	/* Almost all of these are magic "reserved" values.  */
	{ REG_COM5, 0x61 },	{ REG_COM6, 0x4b },
	{ 0x16, 0x02 },		{ REG_MVFP, 0x07 },
	{ 0x21, 0x02 },		{ 0x22, 0x91 },
	{ 0x29, 0x07 },		{ 0x33, 0x0b },
	{ 0x35, 0x0b },		{ 0x37, 0x1d },
	{ 0x38, 0x71 },		{ 0x39, 0x2a },
	{ REG_COM12, 0x78 },	{ 0x4d, 0x40 },
	{ 0x4e, 0x20 },		{ REG_GFIX, 0 },
	{ 0x6b, 0x4a },		{ 0x74, 0x10 },
	{ 0x8d, 0x4f },		{ 0x8e, 0 },
	{ 0x8f, 0 },		{ 0x90, 0 },
	{ 0x91, 0 },		{ 0x96, 0 },
	{ 0x9a, 0 },		{ 0xb0, 0x84 },
	{ 0xb1, 0x0c },		{ 0xb2, 0x0e },
	{ 0xb3, 0x82 },		{ 0xb8, 0x0a },

	/* More reserved magic, some of which tweaks white balance */
	{ 0x43, 0x0a },		{ 0x44, 0xf0 },
	{ 0x45, 0x34 },		{ 0x46, 0x58 },
	{ 0x47, 0x28 },		{ 0x48, 0x3a },
	{ 0x59, 0x88 },		{ 0x5a, 0x88 },
	{ 0x5b, 0x44 },		{ 0x5c, 0x67 },
	{ 0x5d, 0x49 },		{ 0x5e, 0x0e },
	{ 0x6c, 0x0a },		{ 0x6d, 0x55 },
	{ 0x6e, 0x11 },		{ 0x6f, 0x9f }, /* "9e for advance AWB" */
	{ 0x6a, 0x40 },		{ REG_BLUE, 0x40 },
	{ REG_RED, 0x60 },
	{ REG_COM8, COM8_FASTAEC|COM8_AECSTEP|COM8_BFILT|COM8_AGC|COM8_AEC|COM8_AWB },

	/* Matrix coefficients */
	{ 0x4f, 0x80 },		{ 0x50, 0x80 },
	{ 0x51, 0 },		{ 0x52, 0x22 },
	{ 0x53, 0x5e },		{ 0x54, 0x80 },
	{ 0x58, 0x9e },

	{ REG_COM16, COM16_AWBGAIN },	{ REG_EDGE, 0 },
	{ 0x75, 0x05 },		{ 0x76, 0xe1 },
	{ 0x4c, 0 },		{ 0x77, 0x01 },
	{ REG_COM13, 0xc3 },	{ 0x4b, 0x09 },
	{ 0xc9, 0x60 },		{ REG_COM16, 0x38 },
	{ 0x56, 0x40 },

	{ 0x34, 0x11 },		{ REG_COM11, COM11_EXP|COM11_HZAUTO },
	{ 0xa4, 0x88 },		{ 0x96, 0 },
	{ 0x97, 0x30 },		{ 0x98, 0x20 },
	{ 0x99, 0x30 },		{ 0x9a, 0x84 },
	{ 0x9b, 0x29 },		{ 0x9c, 0x03 },
	{ 0x9d, 0x4c },		{ 0x9e, 0x3f },
	{ 0x78, 0x04 },

	/* Extra-weird stuff.  Some sort of multiplexor register */
	{ 0x79, 0x01 },		{ 0xc8, 0xf0 },
	{ 0x79, 0x0f },		{ 0xc8, 0x00 },
	{ 0x79, 0x10 },		{ 0xc8, 0x7e },
	{ 0x79, 0x0a },		{ 0xc8, 0x80 },
	{ 0x79, 0x0b },		{ 0xc8, 0x01 },
	{ 0x79, 0x0c },		{ 0xc8, 0x0f },
	{ 0x79, 0x0d },		{ 0xc8, 0x20 },
	{ 0x79, 0x09 },		{ 0xc8, 0x80 },
	{ 0x79, 0x02 },		{ 0xc8, 0xc0 },
	{ 0x79, 0x03 },		{ 0xc8, 0x40 },
	{ 0x79, 0x05 },		{ 0xc8, 0x30 },
	{ 0x79, 0x26 },

	{ 0xff, 0xff },	/* END MARKER */
};


/*
 * Here we'll try to encapsulate the changes for just the output
 * video format.
 *
 * RGB656 and YUV422 come from OV; RGB444 is homebrewed.
 *
 * IMPORTANT RULE: the first entry must be for COM7, see ov7670_s_fmt for why.
 */


static struct regval_list ov7670_fmt_yuv422[] = {
	{ REG_COM7, 0x0 },  /* Selects YUV mode */
	{ REG_RGB444, 0 },	/* No RGB444 please */
	{ REG_COM1, 0 },	/* CCIR601 */
	{ REG_COM15, COM15_R00FF },
	{ REG_COM9, 0x48 }, /* 32x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0x80 },		/* "matrix coefficient 1" */
	{ 0x50, 0x80 },		/* "matrix coefficient 2" */
	{ 0x51, 0    },		/* vb */
	{ 0x52, 0x22 },		/* "matrix coefficient 4" */
	{ 0x53, 0x5e },		/* "matrix coefficient 5" */
	{ 0x54, 0x80 },		/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT },
	{ 0xff, 0xff },
};

static struct regval_list ov7670_fmt_rgb565[] = {
	{ REG_COM7, COM7_RGB },	/* Selects RGB mode */
	{ REG_RGB444, 0 },	/* No RGB444 please */
	{ REG_COM1, 0x0 },	/* CCIR601 */
	{ REG_COM15, COM15_RGB565 },
	{ REG_COM9, 0x38 },	/* 16x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0xb3 },		/* "matrix coefficient 1" */
	{ 0x50, 0xb3 },		/* "matrix coefficient 2" */
	{ 0x51, 0    },		/* vb */
	{ 0x52, 0x3d },		/* "matrix coefficient 4" */
	{ 0x53, 0xa7 },		/* "matrix coefficient 5" */
	{ 0x54, 0xe4 },		/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT },
	{ 0xff, 0xff },
};

static struct regval_list ov7670_fmt_rgb444[] = {
	{ REG_COM7, COM7_RGB },	/* Selects RGB mode */
	{ REG_RGB444, R444_ENABLE },	/* Enable xxxxrrrr ggggbbbb */
	{ REG_COM1, 0x0 },	/* CCIR601 */
	{ REG_COM15, COM15_R01FE|COM15_RGB565 }, /* Data range needed? */
	{ REG_COM9, 0x38 },	/* 16x gain ceiling; 0x8 is reserved bit */
	{ 0x4f, 0xb3 },		/* "matrix coefficient 1" */
	{ 0x50, 0xb3 },		/* "matrix coefficient 2" */
	{ 0x51, 0    },		/* vb */
	{ 0x52, 0x3d },		/* "matrix coefficient 4" */
	{ 0x53, 0xa7 },		/* "matrix coefficient 5" */
	{ 0x54, 0xe4 },		/* "matrix coefficient 6" */
	{ REG_COM13, COM13_GAMMA|COM13_UVSAT|0x2 },  /* Magic rsvd bit */
	{ 0xff, 0xff },
};

static struct regval_list ov7670_fmt_raw[] = {
	{ REG_COM7, COM7_BAYER },
	{ REG_COM13, 0x08 }, /* No gamma, magic rsvd bit */
	{ REG_COM16, 0x3d }, /* Edge enhancement, denoise */
	{ REG_REG76, 0xe1 }, /* Pix correction, magic rsvd */
	{ 0xff, 0xff },
};



/*
 * Low-level register I/O.
 *
 * Note that there are two versions of these.  On the XO 1, the
 * i2c controller only does SMBUS, so that's what we use.  The
 * ov7670 is not really an SMBUS device, though, so the communication
 * is not always entirely reliable.
 */
static int ov7670_read_smbus(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char *value)
{
	struct i2c_client *client = v4l2_get_subdevdata(sd);
	int ret;

	ret = i2c_smbus_read_byte_data(client, reg);
	if (ret >= 0) {
		*value = (unsigned char)ret;
		ret = 0;
	}
	return ret;
}


static int ov7670_write_smbus(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char value)
{
	struct i2c_client *client = v4l2_get_subdevdata(sd);
	int ret = i2c_smbus_write_byte_data(client, reg, value);

	if (reg == REG_COM7 && (value & COM7_RESET))
		msleep(5);  /* Wait for reset to run */
	return ret;
}

/*
 * On most platforms, we'd rather do straight i2c I/O.
 */
static int ov7670_read_i2c(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char *value)
{
	struct i2c_client *client = v4l2_get_subdevdata(sd);
	u8 data = reg;
	struct i2c_msg msg;
	int ret;

	/*
	 * Send out the register address...
	 */
	msg.addr = client->addr;
	msg.flags = 0;
	msg.len = 1;
	msg.buf = &data;
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret < 0) {
		printk(KERN_ERR "Error %d on register write\n", ret);
		return ret;
	}
	/*
	 * ...then read back the result.
	 */
	msg.flags = I2C_M_RD;
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret >= 0) {
		*value = data;
		ret = 0;
	}
	return ret;
}


static int ov7670_write_i2c(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char value)
{
	struct i2c_client *client = v4l2_get_subdevdata(sd);
	struct i2c_msg msg;
	unsigned char data[2] = { reg, value };
	int ret;

	msg.addr = client->addr;
	msg.flags = 0;
	msg.len = 2;
	msg.buf = data;
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret > 0)
		ret = 0;
	if (reg == REG_COM7 && (value & COM7_RESET))
		msleep(5);  /* Wait for reset to run */
	return ret;
}

static int ov7670_read(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char *value)
{
	struct ov7670_info *info = to_state(sd);
	if (info->use_smbus)
		return ov7670_read_smbus(sd, reg, value);
	else
		return ov7670_read_i2c(sd, reg, value);
}

static int ov7670_write(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char value)
{
	struct ov7670_info *info = to_state(sd);
	if (info->use_smbus)
		return ov7670_write_smbus(sd, reg, value);
	else
		return ov7670_write_i2c(sd, reg, value);
}

static int ov7670_update_bits(struct v4l2_subdev *sd, unsigned char reg,
		unsigned char mask, unsigned char value)
{
	unsigned char orig;
	int ret;

	ret = ov7670_read(sd, reg, &orig);
	if (ret)
		return ret;

	return ov7670_write(sd, reg, (orig & ~mask) | (value & mask));
}

/*
 * Write a list of register settings; ff/ff stops the process.
 */
static int ov7670_write_array(struct v4l2_subdev *sd, struct regval_list *vals)
{
	while (vals->reg_num != 0xff || vals->value != 0xff) {
		int ret = ov7670_write(sd, vals->reg_num, vals->value);
		if (ret < 0)
			return ret;
		vals++;
	}
	return 0;
}


/*
 * Stuff that knows about the sensor.
 */
static int ov7670_reset(struct v4l2_subdev *sd, u32 val)
{
	ov7670_write(sd, REG_COM7, COM7_RESET);
	msleep(1);
	return 0;
}


static int ov7670_init(struct v4l2_subdev *sd, u32 val)
{
	return ov7670_write_array(sd, ov7670_default_regs);
}

static int ov7670_detect(struct v4l2_subdev *sd)
{
	unsigned char v;
	int ret;

	ret = ov7670_init(sd, 0);
	if (ret < 0)
		return ret;
	ret = ov7670_read(sd, REG_MIDH, &v);
	if (ret < 0)
		return ret;
	if (v != 0x7f) /* OV manuf. id. */
		return -ENODEV;
	ret = ov7670_read(sd, REG_MIDL, &v);
	if (ret < 0)
		return ret;
	if (v != 0xa2)
		return -ENODEV;
	/*
	 * OK, we know we have an OmniVision chip...but which one?
	 */
	ret = ov7670_read(sd, REG_PID, &v);
	if (ret < 0)
		return ret;
	if (v != 0x76)  /* PID + VER = 0x76 / 0x73 */
		return -ENODEV;
	ret = ov7670_read(sd, REG_VER, &v);
	if (ret < 0)
		return ret;
	if (v != 0x73)  /* PID + VER = 0x76 / 0x73 */
		return -ENODEV;
	return 0;
}


/*
 * Store information about the video data format.  The color matrix
 * is deeply tied into the format, so keep the relevant values here.
 * The magic matrix numbers come from OmniVision.
 */
static struct ov7670_format_struct {
	u32 mbus_code;
	enum v4l2_colorspace colorspace;
	struct regval_list *regs;
	int cmatrix[CMATRIX_LEN];
} ov7670_formats[] = {
	{
		.mbus_code	= MEDIA_BUS_FMT_YUYV8_2X8,
		.colorspace	= V4L2_COLORSPACE_SRGB,
		.regs		= ov7670_fmt_yuv422,
		.cmatrix	= { 128, -128, 0, -34, -94, 128 },
	},
	{
		.mbus_code	= MEDIA_BUS_FMT_RGB444_2X8_PADHI_LE,
		.colorspace	= V4L2_COLORSPACE_SRGB,
		.regs		= ov7670_fmt_rgb444,
		.cmatrix	= { 179, -179, 0, -61, -176, 228 },
	},
	{
		.mbus_code	= MEDIA_BUS_FMT_RGB565_2X8_LE,
		.colorspace	= V4L2_COLORSPACE_SRGB,
		.regs		= ov7670_fmt_rgb565,
		.cmatrix	= { 179, -179, 0, -61, -176, 228 },
	},
	{
		.mbus_code	= MEDIA_BUS_FMT_SBGGR8_1X8,
		.colorspace	= V4L2_COLORSPACE_SRGB,
		.regs		= ov7670_fmt_raw,
		.cmatrix	= { 0, 0, 0, 0, 0, 0 },
	},
};
#define N_OV7670_FMTS ARRAY_SIZE(ov7670_formats)


/*
 * Then there is the issue of window sizes.  Try to capture the info here.
 */

/*
 * QCIF mode is done (by OV) in a very strange way - it actually looks like
 * VGA with weird scaling options - they do *not* use the canned QCIF mode
 * which is allegedly provided by the sensor.  So here's the weird register
 * settings.
 */
static struct regval_list ov7670_qcif_regs[] = {
	{ REG_COM3, COM3_SCALEEN|COM3_DCWEN },
	{ REG_COM3, COM3_DCWEN },
	{ REG_COM14, COM14_DCWEN | 0x01},
	{ 0x73, 0xf1 },
	{ 0xa2, 0x52 },
	{ 0x7b, 0x1c },
	{ 0x7c, 0x28 },
	{ 0x7d, 0x3c },
	{ 0x7f, 0x69 },
	{ REG_COM9, 0x38 },
	{ 0xa1, 0x0b },
	{ 0x74, 0x19 },
	{ 0x9a, 0x80 },
	{ 0x43, 0x14 },
	{ REG_COM13, 0xc0 },
	{ 0xff, 0xff },
};

static struct ov7670_win_size ov7670_win_sizes[] = {
	/* VGA */
	{
		.width		= VGA_WIDTH,
		.height		= VGA_HEIGHT,
		.com7_bit	= COM7_FMT_VGA,
		.hstart		= 158,	/* These values from */
		.hstop		=  14,	/* Omnivision */
		.vstart		=  10,
		.vstop		= 490,
		.regs		= NULL,
	},
	/* CIF */
	{
		.width		= CIF_WIDTH,
		.height		= CIF_HEIGHT,
		.com7_bit	= COM7_FMT_CIF,
		.hstart		= 170,	/* Empirically determined */
		.hstop		=  90,
		.vstart		=  14,
		.vstop		= 494,
		.regs		= NULL,
	},
	/* QVGA */
	{
		.width		= QVGA_WIDTH,
		.height		= QVGA_HEIGHT,
		.com7_bit	= COM7_FMT_QVGA,
		.hstart		= 168,	/* Empirically determined */
		.hstop		=  24,
		.vstart		=  12,
		.vstop		= 492,
		.regs		= NULL,
	},
	/* QCIF */
	{
		.width		= QCIF_WIDTH,
		.height		= QCIF_HEIGHT,
		.com7_bit	= COM7_FMT_VGA, /* see comment above */
		.hstart		= 456,	/* Empirically determined */
		.hstop		=  24,
		.vstart		=  14,
		.vstop		= 494,
		.regs		= ov7670_qcif_regs,
	}
};

static struct ov7670_win_size ov7675_win_sizes[] = {
	/*
	 * Currently, only VGA is supported. Theoretically it could be possible
	 * to support CIF, QVGA and QCIF too. Taking values for ov7670 as a
	 * base and tweak them empirically could be required.
	 */
	{
		.width		= VGA_WIDTH,
		.height		= VGA_HEIGHT,
		.com7_bit	= COM7_FMT_VGA,
		.hstart		= 158,	/* These values from */
		.hstop		=  14,	/* Omnivision */
		.vstart		=  14,  /* Empirically determined */
		.vstop		= 494,
		.regs		= NULL,
	}
};

static void ov7675_get_framerate(struct v4l2_subdev *sd,
				 struct v4l2_fract *tpf)
{
	struct ov7670_info *info = to_state(sd);
	u32 clkrc = info->clkrc;
	int pll_factor;

	if (info->pll_bypass)
		pll_factor = 1;
	else
		pll_factor = PLL_FACTOR;

	clkrc++;
	if (info->fmt->mbus_code == MEDIA_BUS_FMT_SBGGR8_1X8)
		clkrc = (clkrc >> 1);

	tpf->numerator = 1;
	tpf->denominator = (5 * pll_factor * info->clock_speed) /
			(4 * clkrc);
}

static int ov7675_apply_framerate(struct v4l2_subdev *sd)
{
	struct ov7670_info *info = to_state(sd);
	int ret;

	ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
	if (ret < 0)
		return ret;

	return ov7670_write(sd, REG_DBLV,
			    info->pll_bypass ? DBLV_BYPASS : DBLV_X4);
}

static int ov7675_set_framerate(struct v4l2_subdev *sd,
				 struct v4l2_fract *tpf)
{
	struct ov7670_info *info = to_state(sd);
	u32 clkrc;
	int pll_factor;

	/*
	 * The formula is fps = 5/4*pixclk for YUV/RGB and
	 * fps = 5/2*pixclk for RAW.
	 *
	 * pixclk = clock_speed / (clkrc + 1) * PLLfactor
	 *
	 */
	if (tpf->numerator == 0 || tpf->denominator == 0) {
		clkrc = 0;
	} else {
		pll_factor = info->pll_bypass ? 1 : PLL_FACTOR;
		clkrc = (5 * pll_factor * info->clock_speed * tpf->numerator) /
			(4 * tpf->denominator);
		if (info->fmt->mbus_code == MEDIA_BUS_FMT_SBGGR8_1X8)
			clkrc = (clkrc << 1);
		clkrc--;
	}

	/*
	 * The datasheet claims that clkrc = 0 will divide the input clock by 1
	 * but we've checked with an oscilloscope that it divides by 2 instead.
	 * So, if clkrc = 0 just bypass the divider.
	 */
	if (clkrc <= 0)
		clkrc = CLK_EXT;
	else if (clkrc > CLK_SCALE)
		clkrc = CLK_SCALE;
	info->clkrc = clkrc;

	/* Recalculate frame rate */
	ov7675_get_framerate(sd, tpf);

	/*
	 * If the device is not powered up by the host driver do
	 * not apply any changes to H/W at this time. Instead
	 * the framerate will be restored right after power-up.
	 */
	if (info->on)
		return ov7675_apply_framerate(sd);

	return 0;
}

static void ov7670_get_framerate_legacy(struct v4l2_subdev *sd,
				 struct v4l2_fract *tpf)
{
	struct ov7670_info *info = to_state(sd);

	tpf->numerator = 1;
	tpf->denominator = info->clock_speed;
	if ((info->clkrc & CLK_EXT) == 0 && (info->clkrc & CLK_SCALE) > 1)
		tpf->denominator /= (info->clkrc & CLK_SCALE);
}

static int ov7670_set_framerate_legacy(struct v4l2_subdev *sd,
					struct v4l2_fract *tpf)
{
	struct ov7670_info *info = to_state(sd);
	int div;

	if (tpf->numerator == 0 || tpf->denominator == 0)
		div = 1;  /* Reset to full rate */
	else
		div = (tpf->numerator * info->clock_speed) / tpf->denominator;
	if (div == 0)
		div = 1;
	else if (div > CLK_SCALE)
		div = CLK_SCALE;
	info->clkrc = (info->clkrc & 0x80) | div;
	tpf->numerator = 1;
	tpf->denominator = info->clock_speed / div;

	/*
	 * If the device is not powered up by the host driver do
	 * not apply any changes to H/W at this time. Instead
	 * the framerate will be restored right after power-up.
	 */
	if (info->on)
		return ov7670_write(sd, REG_CLKRC, info->clkrc);

	return 0;
}

/*
 * Store a set of start/stop values into the camera.
 */
static int ov7670_set_hw(struct v4l2_subdev *sd, int hstart, int hstop,
		int vstart, int vstop)
{
	int ret;
	unsigned char v;
/*
 * Horizontal: 11 bits, top 8 live in hstart and hstop.  Bottom 3 of
 * hstart are in href[2:0], bottom 3 of hstop in href[5:3].  There is
 * a mystery "edge offset" value in the top two bits of href.
 */
	ret =  ov7670_write(sd, REG_HSTART, (hstart >> 3) & 0xff);
	ret += ov7670_write(sd, REG_HSTOP, (hstop >> 3) & 0xff);
	ret += ov7670_read(sd, REG_HREF, &v);
	v = (v & 0xc0) | ((hstop & 0x7) << 3) | (hstart & 0x7);
	msleep(10);
	ret += ov7670_write(sd, REG_HREF, v);
/*
 * Vertical: similar arrangement, but only 10 bits.
 */
	ret += ov7670_write(sd, REG_VSTART, (vstart >> 2) & 0xff);
	ret += ov7670_write(sd, REG_VSTOP, (vstop >> 2) & 0xff);
	ret += ov7670_read(sd, REG_VREF, &v);
	v = (v & 0xf0) | ((vstop & 0x3) << 2) | (vstart & 0x3);
	msleep(10);
	ret += ov7670_write(sd, REG_VREF, v);
	return ret;
}


static int ov7670_enum_mbus_code(struct v4l2_subdev *sd,
		struct v4l2_subdev_pad_config *cfg,
		struct v4l2_subdev_mbus_code_enum *code)
{
	if (code->pad || code->index >= N_OV7670_FMTS)
		return -EINVAL;

	code->code = ov7670_formats[code->index].mbus_code;
	return 0;
}

static int ov7670_try_fmt_internal(struct v4l2_subdev *sd,
		struct v4l2_mbus_framefmt *fmt,
		struct ov7670_format_struct **ret_fmt,
		struct ov7670_win_size **ret_wsize)
{
	int index, i;
	struct ov7670_win_size *wsize;
	struct ov7670_info *info = to_state(sd);
	unsigned int n_win_sizes = info->devtype->n_win_sizes;
	unsigned int win_sizes_limit = n_win_sizes;

	for (index = 0; index < N_OV7670_FMTS; index++)
		if (ov7670_formats[index].mbus_code == fmt->code)
			break;
	if (index >= N_OV7670_FMTS) {
		/* default to first format */
		index = 0;
		fmt->code = ov7670_formats[0].mbus_code;
	}
	if (ret_fmt != NULL)
		*ret_fmt = ov7670_formats + index;
	/*
	 * Fields: the OV devices claim to be progressive.
	 */
	fmt->field = V4L2_FIELD_NONE;

	/*
	 * Don't consider values that don't match min_height and min_width
	 * constraints.
	 */
	if (info->min_width || info->min_height)
		for (i = 0; i < n_win_sizes; i++) {
			wsize = info->devtype->win_sizes + i;

			if (wsize->width < info->min_width ||
				wsize->height < info->min_height) {
				win_sizes_limit = i;
				break;
			}
		}
	/*
	 * Round requested image size down to the nearest
	 * we support, but not below the smallest.
	 */
	for (wsize = info->devtype->win_sizes;
	     wsize < info->devtype->win_sizes + win_sizes_limit; wsize++)
		if (fmt->width >= wsize->width && fmt->height >= wsize->height)
			break;
	if (wsize >= info->devtype->win_sizes + win_sizes_limit)
		wsize--;   /* Take the smallest one */
	if (ret_wsize != NULL)
		*ret_wsize = wsize;
	/*
	 * Note the size we'll actually handle.
	 */
	fmt->width = wsize->width;
	fmt->height = wsize->height;
	fmt->colorspace = ov7670_formats[index].colorspace;

	info->format = *fmt;

	return 0;
}

static int ov7670_apply_fmt(struct v4l2_subdev *sd)
{
	struct ov7670_info *info = to_state(sd);
	struct ov7670_win_size *wsize = info->wsize;
	unsigned char com7, com10 = 0;
	int ret;

	/*
	 * COM7 is a pain in the ass, it doesn't like to be read then
	 * quickly written afterward.  But we have everything we need
	 * to set it absolutely here, as long as the format-specific
	 * register sets list it first.
	 */
	com7 = info->fmt->regs[0].value;
	com7 |= wsize->com7_bit;
	ret = ov7670_write(sd, REG_COM7, com7);
	if (ret)
		return ret;

	/*
	 * Configure the media bus through COM10 register
	 */
	if (info->mbus_config & V4L2_MBUS_VSYNC_ACTIVE_LOW)
		com10 |= COM10_VS_NEG;
	if (info->mbus_config & V4L2_MBUS_HSYNC_ACTIVE_LOW)
		com10 |= COM10_HREF_REV;
	if (info->pclk_hb_disable)
		com10 |= COM10_PCLK_HB;
	ret = ov7670_write(sd, REG_COM10, com10);
	if (ret)
		return ret;

	/*
	 * Now write the rest of the array.  Also store start/stops
	 */
	ret = ov7670_write_array(sd, info->fmt->regs + 1);
	if (ret)
		return ret;

	ret = ov7670_set_hw(sd, wsize->hstart, wsize->hstop, wsize->vstart,
			    wsize->vstop);
	if (ret)
		return ret;

	if (wsize->regs) {
		ret = ov7670_write_array(sd, wsize->regs);
		if (ret)
			return ret;
	}

	/*
	 * If we're running RGB565, we must rewrite clkrc after setting
	 * the other parameters or the image looks poor.  If we're *not*
	 * doing RGB565, we must not rewrite clkrc or the image looks
	 * *really* poor.
	 *
	 * (Update) Now that we retain clkrc state, we should be able
	 * to write it unconditionally, and that will make the frame
	 * rate persistent too.
	 */
	ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
	if (ret)
		return ret;

	return 0;
}

/*
 * Set a format.
 */
static int ov7670_set_fmt(struct v4l2_subdev *sd,
		struct v4l2_subdev_pad_config *cfg,
		struct v4l2_subdev_format *format)
{
	struct ov7670_info *info = to_state(sd);
#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
	struct v4l2_mbus_framefmt *mbus_fmt;
#endif
	int ret;

	if (format->pad)
		return -EINVAL;

	if (format->which == V4L2_SUBDEV_FORMAT_TRY) {
		ret = ov7670_try_fmt_internal(sd, &format->format, NULL, NULL);
		if (ret)
			return ret;
#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
		mbus_fmt = v4l2_subdev_get_try_format(sd, cfg, format->pad);
		*mbus_fmt = format->format;
#endif
		return 0;
	}

	ret = ov7670_try_fmt_internal(sd, &format->format, &info->fmt, &info->wsize);
	if (ret)
		return ret;

	/*
	 * If the device is not powered up by the host driver do
	 * not apply any changes to H/W at this time. Instead
	 * the frame format will be restored right after power-up.
	 */
	if (info->on)
		return ov7670_apply_fmt(sd);

	return 0;
}

static int ov7670_get_fmt(struct v4l2_subdev *sd,
			  struct v4l2_subdev_pad_config *cfg,
			  struct v4l2_subdev_format *format)
{
	struct ov7670_info *info = to_state(sd);
#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
	struct v4l2_mbus_framefmt *mbus_fmt;
#endif

	if (format->which == V4L2_SUBDEV_FORMAT_TRY) {
#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
		mbus_fmt = v4l2_subdev_get_try_format(sd, cfg, 0);
		format->format = *mbus_fmt;
		return 0;
#else
		return -EINVAL;
#endif
	} else {
		format->format = info->format;
	}

	return 0;
}

/*
 * Implement G/S_PARM.  There is a "high quality" mode we could try
 * to do someday; for now, we just do the frame rate tweak.
 */
static int ov7670_g_frame_interval(struct v4l2_subdev *sd,
				   struct v4l2_subdev_frame_interval *ival)
{
	struct ov7670_info *info = to_state(sd);


	info->devtype->get_framerate(sd, &ival->interval);

	return 0;
}

static int ov7670_s_frame_interval(struct v4l2_subdev *sd,
				   struct v4l2_subdev_frame_interval *ival)
{
	struct v4l2_fract *tpf = &ival->interval;
	struct ov7670_info *info = to_state(sd);


	return info->devtype->set_framerate(sd, tpf);
}


/*
 * Frame intervals.  Since frame rates are controlled with the clock
 * divider, we can only do 30/n for integer n values.  So no continuous
 * or stepwise options.  Here we just pick a handful of logical values.
 */

static int ov7670_frame_rates[] = { 30, 15, 10, 5, 1 };

static int ov7670_enum_frame_interval(struct v4l2_subdev *sd,
				      struct v4l2_subdev_pad_config *cfg,
				      struct v4l2_subdev_frame_interval_enum *fie)
{
	struct ov7670_info *info = to_state(sd);
	unsigned int n_win_sizes = info->devtype->n_win_sizes;
	int i;

	if (fie->pad)
		return -EINVAL;
	if (fie->index >= ARRAY_SIZE(ov7670_frame_rates))
		return -EINVAL;

	/*
	 * Check if the width/height is valid.
	 *
	 * If a minimum width/height was requested, filter out the capture
	 * windows that fall outside that.
	 */
	for (i = 0; i < n_win_sizes; i++) {
		struct ov7670_win_size *win = &info->devtype->win_sizes[i];

		if (info->min_width && win->width < info->min_width)
			continue;
		if (info->min_height && win->height < info->min_height)
			continue;
		if (fie->width == win->width && fie->height == win->height)
			break;
	}
	if (i == n_win_sizes)
		return -EINVAL;
	fie->interval.numerator = 1;
	fie->interval.denominator = ov7670_frame_rates[fie->index];
	return 0;
}

/*
 * Frame size enumeration
 */
static int ov7670_enum_frame_size(struct v4l2_subdev *sd,
				  struct v4l2_subdev_pad_config *cfg,
				  struct v4l2_subdev_frame_size_enum *fse)
{
	struct ov7670_info *info = to_state(sd);
	int i;
	int num_valid = -1;
	__u32 index = fse->index;
	unsigned int n_win_sizes = info->devtype->n_win_sizes;

	if (fse->pad)
		return -EINVAL;

	/*
	 * If a minimum width/height was requested, filter out the capture
	 * windows that fall outside that.
	 */
	for (i = 0; i < n_win_sizes; i++) {
		struct ov7670_win_size *win = &info->devtype->win_sizes[i];
		if (info->min_width && win->width < info->min_width)
			continue;
		if (info->min_height && win->height < info->min_height)
			continue;
		if (index == ++num_valid) {
			fse->min_width = fse->max_width = win->width;
			fse->min_height = fse->max_height = win->height;
			return 0;
		}
	}

	return -EINVAL;
}

/*
 * Code for dealing with controls.
 */

static int ov7670_store_cmatrix(struct v4l2_subdev *sd,
		int matrix[CMATRIX_LEN])
{
	int i, ret;
	unsigned char signbits = 0;

	/*
	 * Weird crap seems to exist in the upper part of
	 * the sign bits register, so let's preserve it.
	 */
	ret = ov7670_read(sd, REG_CMATRIX_SIGN, &signbits);
	signbits &= 0xc0;

	for (i = 0; i < CMATRIX_LEN; i++) {
		unsigned char raw;

		if (matrix[i] < 0) {
			signbits |= (1 << i);
			if (matrix[i] < -255)
				raw = 0xff;
			else
				raw = (-1 * matrix[i]) & 0xff;
		}
		else {
			if (matrix[i] > 255)
				raw = 0xff;
			else
				raw = matrix[i] & 0xff;
		}
		ret += ov7670_write(sd, REG_CMATRIX_BASE + i, raw);
	}
	ret += ov7670_write(sd, REG_CMATRIX_SIGN, signbits);
	return ret;
}


/*
 * Hue also requires messing with the color matrix.  It also requires
 * trig functions, which tend not to be well supported in the kernel.
 * So here is a simple table of sine values, 0-90 degrees, in steps
 * of five degrees.  Values are multiplied by 1000.
 *
 * The following naive approximate trig functions require an argument
 * carefully limited to -180 <= theta <= 180.
 */
#define SIN_STEP 5
static const int ov7670_sin_table[] = {
	   0,	 87,   173,   258,   342,   422,
	 499,	573,   642,   707,   766,   819,
	 866,	906,   939,   965,   984,   996,
	1000
};

static int ov7670_sine(int theta)
{
	int chs = 1;
	int sine;

	if (theta < 0) {
		theta = -theta;
		chs = -1;
	}
	if (theta <= 90)
		sine = ov7670_sin_table[theta/SIN_STEP];
	else {
		theta -= 90;
		sine = 1000 - ov7670_sin_table[theta/SIN_STEP];
	}
	return sine*chs;
}

static int ov7670_cosine(int theta)
{
	theta = 90 - theta;
	if (theta > 180)
		theta -= 360;
	else if (theta < -180)
		theta += 360;
	return ov7670_sine(theta);
}




static void ov7670_calc_cmatrix(struct ov7670_info *info,
		int matrix[CMATRIX_LEN], int sat, int hue)
{
	int i;
	/*
	 * Apply the current saturation setting first.
	 */
	for (i = 0; i < CMATRIX_LEN; i++)
		matrix[i] = (info->fmt->cmatrix[i] * sat) >> 7;
	/*
	 * Then, if need be, rotate the hue value.
	 */
	if (hue != 0) {
		int sinth, costh, tmpmatrix[CMATRIX_LEN];

		memcpy(tmpmatrix, matrix, CMATRIX_LEN*sizeof(int));
		sinth = ov7670_sine(hue);
		costh = ov7670_cosine(hue);

		matrix[0] = (matrix[3]*sinth + matrix[0]*costh)/1000;
		matrix[1] = (matrix[4]*sinth + matrix[1]*costh)/1000;
		matrix[2] = (matrix[5]*sinth + matrix[2]*costh)/1000;
		matrix[3] = (matrix[3]*costh - matrix[0]*sinth)/1000;
		matrix[4] = (matrix[4]*costh - matrix[1]*sinth)/1000;
		matrix[5] = (matrix[5]*costh - matrix[2]*sinth)/1000;
	}
}



static int ov7670_s_sat_hue(struct v4l2_subdev *sd, int sat, int hue)
{
	struct ov7670_info *info = to_state(sd);
	int matrix[CMATRIX_LEN];
	int ret;

	ov7670_calc_cmatrix(info, matrix, sat, hue);
	ret = ov7670_store_cmatrix(sd, matrix);
	return ret;
}


/*
 * Some weird registers seem to store values in a sign/magnitude format!
 */

static unsigned char ov7670_abs_to_sm(unsigned char v)
{
	if (v > 127)
		return v & 0x7f;
	return (128 - v) | 0x80;
}

static int ov7670_s_brightness(struct v4l2_subdev *sd, int value)
{
	unsigned char com8 = 0, v;
	int ret;

	ov7670_read(sd, REG_COM8, &com8);
	com8 &= ~COM8_AEC;
	ov7670_write(sd, REG_COM8, com8);
	v = ov7670_abs_to_sm(value);
	ret = ov7670_write(sd, REG_BRIGHT, v);
	return ret;
}

static int ov7670_s_contrast(struct v4l2_subdev *sd, int value)
{
	return ov7670_write(sd, REG_CONTRAS, (unsigned char) value);
}

static int ov7670_s_hflip(struct v4l2_subdev *sd, int value)
{
	unsigned char v = 0;
	int ret;

	ret = ov7670_read(sd, REG_MVFP, &v);
	if (value)
		v |= MVFP_MIRROR;
	else
		v &= ~MVFP_MIRROR;
	msleep(10);  /* FIXME */
	ret += ov7670_write(sd, REG_MVFP, v);
	return ret;
}

static int ov7670_s_vflip(struct v4l2_subdev *sd, int value)
{
	unsigned char v = 0;
	int ret;

	ret = ov7670_read(sd, REG_MVFP, &v);
	if (value)
		v |= MVFP_FLIP;
	else
		v &= ~MVFP_FLIP;
	msleep(10);  /* FIXME */
	ret += ov7670_write(sd, REG_MVFP, v);
	return ret;
}

/*
 * GAIN is split between REG_GAIN and REG_VREF[7:6].  If one believes
 * the data sheet, the VREF parts should be the most significant, but
 * experience shows otherwise.  There seems to be little value in
 * messing with the VREF bits, so we leave them alone.
 */
static int ov7670_g_gain(struct v4l2_subdev *sd, __s32 *value)
{
	int ret;
	unsigned char gain;

	ret = ov7670_read(sd, REG_GAIN, &gain);
	*value = gain;
	return ret;
}

static int ov7670_s_gain(struct v4l2_subdev *sd, int value)
{
	int ret;
	unsigned char com8;

	ret = ov7670_write(sd, REG_GAIN, value & 0xff);
	/* Have to turn off AGC as well */
	if (ret == 0) {
		ret = ov7670_read(sd, REG_COM8, &com8);
		ret = ov7670_write(sd, REG_COM8, com8 & ~COM8_AGC);
	}
	return ret;
}

/*
 * Tweak autogain.
 */
static int ov7670_s_autogain(struct v4l2_subdev *sd, int value)
{
	int ret;
	unsigned char com8;

	ret = ov7670_read(sd, REG_COM8, &com8);
	if (ret == 0) {
		if (value)
			com8 |= COM8_AGC;
		else
			com8 &= ~COM8_AGC;
		ret = ov7670_write(sd, REG_COM8, com8);
	}
	return ret;
}

static int ov7670_s_exp(struct v4l2_subdev *sd, int value)
{
	int ret;
	unsigned char com1, com8, aech, aechh;

	ret = ov7670_read(sd, REG_COM1, &com1) +
		ov7670_read(sd, REG_COM8, &com8) +
		ov7670_read(sd, REG_AECHH, &aechh);
	if (ret)
		return ret;

	com1 = (com1 & 0xfc) | (value & 0x03);
	aech = (value >> 2) & 0xff;
	aechh = (aechh & 0xc0) | ((value >> 10) & 0x3f);
	ret = ov7670_write(sd, REG_COM1, com1) +
		ov7670_write(sd, REG_AECH, aech) +
		ov7670_write(sd, REG_AECHH, aechh);
	/* Have to turn off AEC as well */
	if (ret == 0)
		ret = ov7670_write(sd, REG_COM8, com8 & ~COM8_AEC);
	return ret;
}

/*
 * Tweak autoexposure.
 */
static int ov7670_s_autoexp(struct v4l2_subdev *sd,
		enum v4l2_exposure_auto_type value)
{
	int ret;
	unsigned char com8;

	ret = ov7670_read(sd, REG_COM8, &com8);
	if (ret == 0) {
		if (value == V4L2_EXPOSURE_AUTO)
			com8 |= COM8_AEC;
		else
			com8 &= ~COM8_AEC;
		ret = ov7670_write(sd, REG_COM8, com8);
	}
	return ret;
}

static const char * const ov7670_test_pattern_menu[] = {
	"No test output",
	"Shifting \"1\"",
	"8-bar color bar",
	"Fade to gray color bar",
};

static int ov7670_s_test_pattern(struct v4l2_subdev *sd, int value)
{
	int ret;

	ret = ov7670_update_bits(sd, REG_SCALING_XSC, TEST_PATTTERN_0,
				value & BIT(0) ? TEST_PATTTERN_0 : 0);
	if (ret)
		return ret;

	return ov7670_update_bits(sd, REG_SCALING_YSC, TEST_PATTTERN_1,
				value & BIT(1) ? TEST_PATTTERN_1 : 0);
}

static int ov7670_g_volatile_ctrl(struct v4l2_ctrl *ctrl)
{
	struct v4l2_subdev *sd = to_sd(ctrl);
	struct ov7670_info *info = to_state(sd);

	switch (ctrl->id) {
	case V4L2_CID_AUTOGAIN:
		return ov7670_g_gain(sd, &info->gain->val);
	}
	return -EINVAL;
}

static int ov7670_s_ctrl(struct v4l2_ctrl *ctrl)
{
	struct v4l2_subdev *sd = to_sd(ctrl);
	struct ov7670_info *info = to_state(sd);

	switch (ctrl->id) {
	case V4L2_CID_BRIGHTNESS:
		return ov7670_s_brightness(sd, ctrl->val);
	case V4L2_CID_CONTRAST:
		return ov7670_s_contrast(sd, ctrl->val);
	case V4L2_CID_SATURATION:
		return ov7670_s_sat_hue(sd,
				info->saturation->val, info->hue->val);
	case V4L2_CID_VFLIP:
		return ov7670_s_vflip(sd, ctrl->val);
	case V4L2_CID_HFLIP:
		return ov7670_s_hflip(sd, ctrl->val);
	case V4L2_CID_AUTOGAIN:
		/* Only set manual gain if auto gain is not explicitly
		   turned on. */
		if (!ctrl->val) {
			/* ov7670_s_gain turns off auto gain */
			return ov7670_s_gain(sd, info->gain->val);
		}
		return ov7670_s_autogain(sd, ctrl->val);
	case V4L2_CID_EXPOSURE_AUTO:
		/* Only set manual exposure if auto exposure is not explicitly
		   turned on. */
		if (ctrl->val == V4L2_EXPOSURE_MANUAL) {
			/* ov7670_s_exp turns off auto exposure */
			return ov7670_s_exp(sd, info->exposure->val);
		}
		return ov7670_s_autoexp(sd, ctrl->val);
	case V4L2_CID_TEST_PATTERN:
		return ov7670_s_test_pattern(sd, ctrl->val);
	}
	return -EINVAL;
}

static const struct v4l2_ctrl_ops ov7670_ctrl_ops = {
	.s_ctrl = ov7670_s_ctrl,
	.g_volatile_ctrl = ov7670_g_volatile_ctrl,
};

#ifdef CONFIG_VIDEO_ADV_DEBUG
static int ov7670_g_register(struct v4l2_subdev *sd, struct v4l2_dbg_register *reg)
{
	unsigned char val = 0;
	int ret;

	ret = ov7670_read(sd, reg->reg & 0xff, &val);
	reg->val = val;
	reg->size = 1;
	return ret;
}

static int ov7670_s_register(struct v4l2_subdev *sd, const struct v4l2_dbg_register *reg)
{
	ov7670_write(sd, reg->reg & 0xff, reg->val & 0xff);
	return 0;
}
#endif

static void ov7670_power_on(struct v4l2_subdev *sd)
{
	struct ov7670_info *info = to_state(sd);

	if (info->on)
		return;

	clk_prepare_enable(info->clk);

	if (info->pwdn_gpio)
		gpiod_set_value(info->pwdn_gpio, 0);
	if (info->resetb_gpio) {
		gpiod_set_value(info->resetb_gpio, 1);
		usleep_range(500, 1000);
		gpiod_set_value(info->resetb_gpio, 0);
	}
	if (info->pwdn_gpio || info->resetb_gpio || info->clk)
		usleep_range(3000, 5000);

	info->on = true;
}

static void ov7670_power_off(struct v4l2_subdev *sd)
{
	struct ov7670_info *info = to_state(sd);

	if (!info->on)
		return;

	clk_disable_unprepare(info->clk);

	if (info->pwdn_gpio)
		gpiod_set_value(info->pwdn_gpio, 1);

	info->on = false;
}

static int ov7670_s_power(struct v4l2_subdev *sd, int on)
{
	struct ov7670_info *info = to_state(sd);

	if (info->on == on)
		return 0;

	if (on) {
		ov7670_power_on (sd);
		ov7670_init(sd, 0);
		ov7670_apply_fmt(sd);
		ov7675_apply_framerate(sd);
		v4l2_ctrl_handler_setup(&info->hdl);
	} else {
		ov7670_power_off (sd);
	}

	return 0;
}

static void ov7670_get_default_format(struct v4l2_subdev *sd,
				      struct v4l2_mbus_framefmt *format)
{
	struct ov7670_info *info = to_state(sd);

	format->width = info->devtype->win_sizes[0].width;
	format->height = info->devtype->win_sizes[0].height;
	format->colorspace = info->fmt->colorspace;
	format->code = info->fmt->mbus_code;
	format->field = V4L2_FIELD_NONE;
}

#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
static int ov7670_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
{
	struct v4l2_mbus_framefmt *format =
				v4l2_subdev_get_try_format(sd, fh->pad, 0);

	ov7670_get_default_format(sd, format);

	return 0;
}
#endif

/* ----------------------------------------------------------------------- */

static const struct v4l2_subdev_core_ops ov7670_core_ops = {
	.reset = ov7670_reset,
	.init = ov7670_init,
	.s_power = ov7670_s_power,
	.log_status = v4l2_ctrl_subdev_log_status,
	.subscribe_event = v4l2_ctrl_subdev_subscribe_event,
	.unsubscribe_event = v4l2_event_subdev_unsubscribe,
#ifdef CONFIG_VIDEO_ADV_DEBUG
	.g_register = ov7670_g_register,
	.s_register = ov7670_s_register,
#endif
};

static const struct v4l2_subdev_video_ops ov7670_video_ops = {
	.s_frame_interval = ov7670_s_frame_interval,
	.g_frame_interval = ov7670_g_frame_interval,
};

static const struct v4l2_subdev_pad_ops ov7670_pad_ops = {
	.enum_frame_interval = ov7670_enum_frame_interval,
	.enum_frame_size = ov7670_enum_frame_size,
	.enum_mbus_code = ov7670_enum_mbus_code,
	.get_fmt = ov7670_get_fmt,
	.set_fmt = ov7670_set_fmt,
};

static const struct v4l2_subdev_ops ov7670_ops = {
	.core = &ov7670_core_ops,
	.video = &ov7670_video_ops,
	.pad = &ov7670_pad_ops,
};

#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
static const struct v4l2_subdev_internal_ops ov7670_subdev_internal_ops = {
	.open = ov7670_open,
};
#endif

/* ----------------------------------------------------------------------- */

static const struct ov7670_devtype ov7670_devdata[] = {
	[MODEL_OV7670] = {
		.win_sizes = ov7670_win_sizes,
		.n_win_sizes = ARRAY_SIZE(ov7670_win_sizes),
		.set_framerate = ov7670_set_framerate_legacy,
		.get_framerate = ov7670_get_framerate_legacy,
	},
	[MODEL_OV7675] = {
		.win_sizes = ov7675_win_sizes,
		.n_win_sizes = ARRAY_SIZE(ov7675_win_sizes),
		.set_framerate = ov7675_set_framerate,
		.get_framerate = ov7675_get_framerate,
	},
};

static int ov7670_init_gpio(struct i2c_client *client, struct ov7670_info *info)
{
	info->pwdn_gpio = devm_gpiod_get_optional(&client->dev, "powerdown",
			GPIOD_OUT_LOW);
	if (IS_ERR(info->pwdn_gpio)) {
		dev_info(&client->dev, "can't get %s GPIO\n", "powerdown");
		return PTR_ERR(info->pwdn_gpio);
	}

	info->resetb_gpio = devm_gpiod_get_optional(&client->dev, "reset",
			GPIOD_OUT_LOW);
	if (IS_ERR(info->resetb_gpio)) {
		dev_info(&client->dev, "can't get %s GPIO\n", "reset");
		return PTR_ERR(info->resetb_gpio);
	}

	usleep_range(3000, 5000);

	return 0;
}

/*
 * ov7670_parse_dt() - Parse device tree to collect mbus configuration
 *			properties
 */
static int ov7670_parse_dt(struct device *dev,
			   struct ov7670_info *info)
{
	struct fwnode_handle *fwnode = dev_fwnode(dev);
	struct v4l2_fwnode_endpoint bus_cfg = { .bus_type = 0 };
	struct fwnode_handle *ep;
	int ret;

	if (!fwnode)
		return -EINVAL;

	info->pclk_hb_disable = false;
	if (fwnode_property_present(fwnode, "ov7670,pclk-hb-disable"))
		info->pclk_hb_disable = true;

	ep = fwnode_graph_get_next_endpoint(fwnode, NULL);
	if (!ep)
		return -EINVAL;

	ret = v4l2_fwnode_endpoint_parse(ep, &bus_cfg);
	fwnode_handle_put(ep);
	if (ret)
		return ret;

	if (bus_cfg.bus_type != V4L2_MBUS_PARALLEL) {
		dev_err(dev, "Unsupported media bus type\n");
		return ret;
	}
	info->mbus_config = bus_cfg.bus.parallel.flags;

	return 0;
}

static int ov7670_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct v4l2_fract tpf;
	struct v4l2_subdev *sd;
	struct ov7670_info *info;
	int ret;

	info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
	if (info == NULL)
		return -ENOMEM;
	sd = &info->sd;
	v4l2_i2c_subdev_init(sd, client, &ov7670_ops);

#ifdef CONFIG_VIDEO_V4L2_SUBDEV_API
	sd->internal_ops = &ov7670_subdev_internal_ops;
	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE | V4L2_SUBDEV_FL_HAS_EVENTS;
#endif

	info->clock_speed = 30; /* default: a guess */

	if (dev_fwnode(&client->dev)) {
		ret = ov7670_parse_dt(&client->dev, info);
		if (ret)
			return ret;

	} else if (client->dev.platform_data) {
		struct ov7670_config *config = client->dev.platform_data;

		/*
		 * Must apply configuration before initializing device, because it
		 * selects I/O method.
		 */
		info->min_width = config->min_width;
		info->min_height = config->min_height;
		info->use_smbus = config->use_smbus;

		if (config->clock_speed)
			info->clock_speed = config->clock_speed;

		if (config->pll_bypass)
			info->pll_bypass = true;

		if (config->pclk_hb_disable)
			info->pclk_hb_disable = true;
	}

	info->clk = devm_clk_get(&client->dev, "xclk"); /* optional */
	if (IS_ERR(info->clk)) {
		ret = PTR_ERR(info->clk);
		if (ret == -ENOENT)
			info->clk = NULL;
		else
			return ret;
	}

	ret = ov7670_init_gpio(client, info);
	if (ret)
		return ret;

	ov7670_power_on(sd);

	if (info->clk) {
		info->clock_speed = clk_get_rate(info->clk) / 1000000;
		if (info->clock_speed < 10 || info->clock_speed > 48) {
			ret = -EINVAL;
			goto power_off;
		}
	}

	/* Make sure it's an ov7670 */
	ret = ov7670_detect(sd);
	if (ret) {
		v4l_dbg(1, debug, client,
			"chip found @ 0x%x (%s) is not an ov7670 chip.\n",
			client->addr << 1, client->adapter->name);
		goto power_off;
	}
	v4l_info(client, "chip found @ 0x%02x (%s)\n",
			client->addr << 1, client->adapter->name);

	info->devtype = &ov7670_devdata[id->driver_data];
	info->fmt = &ov7670_formats[0];
	info->wsize = &info->devtype->win_sizes[0];

	ov7670_get_default_format(sd, &info->format);

	info->clkrc = 0;

	/* Set default frame rate to 30 fps */
	tpf.numerator = 1;
	tpf.denominator = 30;
	info->devtype->set_framerate(sd, &tpf);

	v4l2_ctrl_handler_init(&info->hdl, 10);
	v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_BRIGHTNESS, 0, 255, 1, 128);
	v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_CONTRAST, 0, 127, 1, 64);
	v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_VFLIP, 0, 1, 1, 0);
	v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_HFLIP, 0, 1, 1, 0);
	info->saturation = v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_SATURATION, 0, 256, 1, 128);
	info->hue = v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_HUE, -180, 180, 5, 0);
	info->gain = v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_GAIN, 0, 255, 1, 128);
	info->auto_gain = v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_AUTOGAIN, 0, 1, 1, 1);
	info->exposure = v4l2_ctrl_new_std(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_EXPOSURE, 0, 65535, 1, 500);
	info->auto_exposure = v4l2_ctrl_new_std_menu(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_MANUAL, 0,
			V4L2_EXPOSURE_AUTO);
	v4l2_ctrl_new_std_menu_items(&info->hdl, &ov7670_ctrl_ops,
			V4L2_CID_TEST_PATTERN,
			ARRAY_SIZE(ov7670_test_pattern_menu) - 1, 0, 0,
			ov7670_test_pattern_menu);
	sd->ctrl_handler = &info->hdl;
	if (info->hdl.error) {
		ret = info->hdl.error;

		goto hdl_free;
	}
	/*
	 * We have checked empirically that hw allows to read back the gain
	 * value chosen by auto gain but that's not the case for auto exposure.
	 */
	v4l2_ctrl_auto_cluster(2, &info->auto_gain, 0, true);
	v4l2_ctrl_auto_cluster(2, &info->auto_exposure,
			       V4L2_EXPOSURE_MANUAL, false);
	v4l2_ctrl_cluster(2, &info->saturation);

#if defined(CONFIG_MEDIA_CONTROLLER)
	info->pad.flags = MEDIA_PAD_FL_SOURCE;
	info->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;
	ret = media_entity_pads_init(&info->sd.entity, 1, &info->pad);
	if (ret < 0)
		goto hdl_free;
#endif

	v4l2_ctrl_handler_setup(&info->hdl);

	ret = v4l2_async_register_subdev(&info->sd);
	if (ret < 0)
		goto entity_cleanup;

	ov7670_power_off(sd);
	return 0;

entity_cleanup:
	media_entity_cleanup(&info->sd.entity);
hdl_free:
	v4l2_ctrl_handler_free(&info->hdl);
power_off:
	ov7670_power_off(sd);
	return ret;
}

static int ov7670_remove(struct i2c_client *client)
{
	struct v4l2_subdev *sd = i2c_get_clientdata(client);
	struct ov7670_info *info = to_state(sd);

	v4l2_async_unregister_subdev(sd);
	v4l2_ctrl_handler_free(&info->hdl);
	media_entity_cleanup(&info->sd.entity);
	return 0;
}

static const struct i2c_device_id ov7670_id[] = {
	{ "ov7670", MODEL_OV7670 },
	{ "ov7675", MODEL_OV7675 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, ov7670_id);

#if IS_ENABLED(CONFIG_OF)
static const struct of_device_id ov7670_of_match[] = {
	{ .compatible = "ovti,ov7670", },
	{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, ov7670_of_match);
#endif

static struct i2c_driver ov7670_driver = {
	.driver = {
		.name	= "ov7670",
		.of_match_table = of_match_ptr(ov7670_of_match),
	},
	.probe		= ov7670_probe,
	.remove		= ov7670_remove,
	.id_table	= ov7670_id,
};

module_i2c_driver(ov7670_driver);