Documentation/gpu/drm-uapi.rst

9 addition, drivers export device-specific interfaces for use by userspace
10 drivers & device-aware applications through ioctls and sysfs files.
16 Cover generic ioctls and sysfs layout here. We only need high-level
22 .. kernel-doc:: drivers/gpu/drm/drm_ioctl.c
31 .. kernel-doc:: drivers/gpu/drm/drm_auth.c
34 .. kernel-doc:: drivers/gpu/drm/drm_auth.c
37 .. kernel-doc:: include/drm/drm_auth.h
40 Open-Source Userspace Requirements
48 open-sourced userspace patches, and those patches must be reviewed and ready for
66 - The Linux kernel's "no regression" policy holds in practice only for
67   open-source userspace of the DRM subsystem. DRM developers are perfectly fine
68   if closed-source blob drivers in userspace use the same uAPI as the open
73 - Any new userspace interface must have an open-source implementation as
76 The other reason for requiring open-source userspace is uAPI review. Since the
79 both sides. Making sure that the interface indeed covers the use-case fully
82 - The open-source userspace must not be a toy/test application, but the real
87 - The userspace side must be fully reviewed and tested to the standards of that
88   userspace project. For e.g. mesa this means piglit testcases and review on the
90   job done.  The userspace-side reviewer should also provide an Acked-by on the
94 - The userspace patches must be against the canonical upstream, not some vendor
98 - The kernel patch can only be merged after all the above requirements are met,
99   but it **must** be merged to either drm-next or drm-misc-next **before** the
109 for the same thing co-existing. If we add a few more complete mistakes into the
117 DRM core provides multiple character-devices for user-space to use.
118 Depending on which device is opened, user-space can perform a different
130 authenticate to a DRM-Master prior to getting GPU access. To avoid this
134 Only non-global rendering commands are allowed. If a driver supports
141 per device. No ioctls except PRIME-related ioctls will be allowed on
143 nodes are designed to avoid the buffer-leaks, which occur if clients
146 driver-dependent render-only ioctls as DRM_RENDER_ALLOW so render
150 With render nodes, user-space can now control access to the render node
151 via basic file-system access-modes. A running graphics server which
159 DRM-Master concept. There is no reason to associate render clients with
160 a DRM-Master as they are independent of any graphics server. Besides,
164 visible to user-space and accessible beyond open-file boundaries, they
167 Device Hot-Unplug
176 user is able to hot-unplug this kind of devices while they are being
178 damage from hot-unplugging a DRM device needs to be limited as much as
193 (or driver-specific ioctls returning driver-specific things), or open()
211 -------------------------
213 - KMS connectors must change their status to disconnected.
215 - Legacy modesets and pageflips, and atomic commits, both real and
219 - Pending non-blocking KMS operations deliver the DRM events userspace
222 - open() on a device node whose underlying device has disappeared will
225 - Attempting to create a DRM lease on a disappeared DRM device will
229 Requirements for Render and Cross-Device UAPI
230 ---------------------------------------------
232 - All GPU jobs that can no longer run must have their fences
233   force-signalled to avoid inflicting hangs on userspace.
236 - Some userspace APIs already define what should happen when the device
240   driver-specific ioctls and handling those in userspace drivers, or
243 - dmabuf which point to memory that has disappeared will either fail to
248 - Attempting to import a dmabuf to a disappeared device will either fail
252 - open() on a device node whose underlying device has disappeared will
259 ----------------------------
266 dmabuf which might be mapped to other devices (cross-device dmabuf
282 .. kernel-doc:: drivers/gpu/drm/drm_ioctl.c
286 -------------------------------
309         E.g. root-only or much more common, DRM master-only operations return
321         when the exporting driver of a shared dma-buf or fence doesn't support a
335         Catch-all for anything that is an invalid argument combination which
343 .. kernel-doc:: include/drm/drm_ioctl.h
346 .. kernel-doc:: drivers/gpu/drm/drm_ioctl.c
349 .. kernel-doc:: drivers/gpu/drm/drm_ioc32.c
356 --------------------------------------
358 New cross-driver userspace interface extensions, like new IOCTL, new KMS
360 should have driver-agnostic testcases in IGT for that feature, if such a test
364 ---------------------------
370 https://gitlab.freedesktop.org/drm/igt-gpu-tools/.
373 --------------------------
375 VKMS is a software-only model of a KMS driver that is useful for testing
389 It's possible to run the IGT-tests in a VM in two ways:
392 	2. Use IGT from the host machine and write the results in a shared directory.
395 the host machine to run igt-tests. As an example it's used virtme::
397 	$ virtme-run --rwdir /path/for/shared_dir --kdir=path/for/kernel/directory --mods=auto
399 Run the igt-tests in the guest machine, as example it's ran the 'kms_flip'
402 	$ /path/for/igt-gpu-tools/scripts/run-tests.sh -p -s -t "kms_flip.*" -v
404 In this example, instead of build the igt_runner, Piglit is used
405 (-p option); it's created html summary of the tests results and it's saved
406 in the folder "igt-gpu-tools/results"; it's executed only the igt-tests
407 matching the -t option.
410 -------------------
412 .. kernel-doc:: drivers/gpu/drm/drm_debugfs_crc.c
415 .. kernel-doc:: drivers/gpu/drm/drm_debugfs_crc.c
419 ---------------
421 .. kernel-doc:: include/drm/drm_debugfs.h
424 .. kernel-doc:: drivers/gpu/drm/drm_debugfs.c
430 .. kernel-doc:: drivers/gpu/drm/drm_sysfs.c
433 .. kernel-doc:: drivers/gpu/drm/drm_sysfs.c
448     This was only used for user-mode-settind drivers around modesetting
452     call this any more since with kernel mode setting it is a no-op.
457 .. kernel-doc:: include/uapi/drm/drm_mode.h
460 .. kernel-doc:: include/uapi/drm/drm_mode.h