1*4882a593Smuzhiyun======== 2*4882a593Smuzhiyuni2c-stub 3*4882a593Smuzhiyun======== 4*4882a593Smuzhiyun 5*4882a593SmuzhiyunDescription 6*4882a593Smuzhiyun=========== 7*4882a593Smuzhiyun 8*4882a593SmuzhiyunThis module is a very simple fake I2C/SMBus driver. It implements six 9*4882a593Smuzhiyuntypes of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w) 10*4882a593Smuzhiyunword data, (r/w) I2C block data, and (r/w) SMBus block data. 11*4882a593Smuzhiyun 12*4882a593SmuzhiyunYou need to provide chip addresses as a module parameter when loading this 13*4882a593Smuzhiyundriver, which will then only react to SMBus commands to these addresses. 14*4882a593Smuzhiyun 15*4882a593SmuzhiyunNo hardware is needed nor associated with this module. It will accept write 16*4882a593Smuzhiyunquick commands to the specified addresses; it will respond to the other 17*4882a593Smuzhiyuncommands (also to the specified addresses) by reading from or writing to 18*4882a593Smuzhiyunarrays in memory. It will also spam the kernel logs for every command it 19*4882a593Smuzhiyunhandles. 20*4882a593Smuzhiyun 21*4882a593SmuzhiyunA pointer register with auto-increment is implemented for all byte 22*4882a593Smuzhiyunoperations. This allows for continuous byte reads like those supported by 23*4882a593SmuzhiyunEEPROMs, among others. 24*4882a593Smuzhiyun 25*4882a593SmuzhiyunSMBus block command support is disabled by default, and must be enabled 26*4882a593Smuzhiyunexplicitly by setting the respective bits (0x03000000) in the functionality 27*4882a593Smuzhiyunmodule parameter. 28*4882a593Smuzhiyun 29*4882a593SmuzhiyunSMBus block commands must be written to configure an SMBus command for 30*4882a593SmuzhiyunSMBus block operations. Writes can be partial. Block read commands always 31*4882a593Smuzhiyunreturn the number of bytes selected with the largest write so far. 32*4882a593Smuzhiyun 33*4882a593SmuzhiyunThe typical use-case is like this: 34*4882a593Smuzhiyun 35*4882a593Smuzhiyun 1. load this module 36*4882a593Smuzhiyun 2. use i2cset (from the i2c-tools project) to pre-load some data 37*4882a593Smuzhiyun 3. load the target chip driver module 38*4882a593Smuzhiyun 4. observe its behavior in the kernel log 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunThere's a script named i2c-stub-from-dump in the i2c-tools package which 41*4882a593Smuzhiyuncan load register values automatically from a chip dump. 42*4882a593Smuzhiyun 43*4882a593SmuzhiyunParameters 44*4882a593Smuzhiyun========== 45*4882a593Smuzhiyun 46*4882a593Smuzhiyunint chip_addr[10]: 47*4882a593Smuzhiyun The SMBus addresses to emulate chips at. 48*4882a593Smuzhiyun 49*4882a593Smuzhiyununsigned long functionality: 50*4882a593Smuzhiyun Functionality override, to disable some commands. See I2C_FUNC_* 51*4882a593Smuzhiyun constants in <linux/i2c.h> for the suitable values. For example, 52*4882a593Smuzhiyun value 0x1f0000 would only enable the quick, byte and byte data 53*4882a593Smuzhiyun commands. 54*4882a593Smuzhiyun 55*4882a593Smuzhiyunu8 bank_reg[10], u8 bank_mask[10], u8 bank_start[10], u8 bank_end[10]: 56*4882a593Smuzhiyun Optional bank settings. They tell which bits in which register 57*4882a593Smuzhiyun select the active bank, as well as the range of banked registers. 58*4882a593Smuzhiyun 59*4882a593SmuzhiyunCaveats 60*4882a593Smuzhiyun======= 61*4882a593Smuzhiyun 62*4882a593SmuzhiyunIf your target driver polls some byte or word waiting for it to change, the 63*4882a593Smuzhiyunstub could lock it up. Use i2cset to unlock it. 64*4882a593Smuzhiyun 65*4882a593SmuzhiyunIf you spam it hard enough, printk can be lossy. This module really wants 66*4882a593Smuzhiyunsomething like relayfs. 67