[PATCH v3 0/6] drm/xe: Add user commands to WA BB via configfs

[Lucas De Marchi <lucas.demarchi@intel.com>]

Integrate WA BB (aka post context restore bb) with configfs to allow
validation to experiment with the GPU, executing commands on every
context switch.

Setting some registers to experiment:

	# echo 0 > /sys/bus/pci/drivers_autoprobe
	# modprobe xe
	# mkdir  /sys/kernel/config/xe/0000:04:00.0
	# echo '
	rcs cmd 11000001 4F104 DEADDEAD
	rcs reg 4F100 DEADBEEF
	' > /sys/kernel/config/xe/0000\:03\:00.0/ctx_restore_post_bb
	# echo 0000:04:00.0 > /sys/bus/pci/drivers/xe/bind

Testing it worked with intel_reg:

	# intel_reg read mmio:4F100
	(0x0004f100): 0xdeadbeef
	# intel_reg read mmio:4F104
	(0x0004f104): 0xdeaddead

This also prepares the codebase to use the same functions for mid
context restore.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
---
Changes in v3:
- Minor updates on first patches
- Fix kunit build (without CONFIG_CONFIGFS_FS)
- Fix use of binary attributes failing the expectation of a failed write
  producing an error code
- Link to v2: https://lore.kernel.org/r/20250827-wa-bb-cmds-v2-0-3cdf4d63c72a@intel.com

Changes in v2:
- Drop other refactors and fixes already merged
- Add documentation and make sure it works with intel_reg
- Refactor command parsing to be able to easily extend it for other BBs
  to be added in future.
- Link to v1: https://lore.kernel.org/r/20250523-wa-bb-cmds-v1-0-40b337f71bcd@intel.com
---
Lucas De Marchi (6):
      drm/xe: Update workaround documentation
      drm/xe/configfs: Fix documentation warning
      drm/xe/configfs: Extract function to parse engine
      drm/xe/configfs: Allow to select by class only
      drm/xe/lrc: Allow to add user commands on context switch
      drm/xe/configfs: Add post context restore bb

 drivers/gpu/drm/xe/xe_configfs.c | 367 ++++++++++++++++++++++++++++++++++++---
 drivers/gpu/drm/xe/xe_configfs.h |   6 +
 drivers/gpu/drm/xe/xe_lrc.c      |  25 +++
 drivers/gpu/drm/xe/xe_wa.c       |  45 +++--
 4 files changed, 405 insertions(+), 38 deletions(-)

base-commit: 6a483fa08dd4b4f355b65acc8aa24a335baccd2b
change-id: 20250523-wa-bb-cmds-2a81a7121fc2

Lucas De Marchi