[PATCH 2/3] drm: introduce DRIVER_FORCE_AUTH

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

With earlier commits we've removed DRM_AUTH for driver ioctls annotated
with DRM_AUTH | DRM_RENDER_ALLOW, as the protection it introduces is
effectively not existent.

With next commit, we'll effectively do the same for DRM core.

Yet the AMD developers have voiced concerns that by doing so, developers
working on the closed source user-space driver might remove render node
support.

Since we do _not_ want that to happen, add workaround for those two
drivers

Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: amd-gfx at lists.freedesktop.org
Cc: Daniel Vetter <daniel at ffwll.ch>
Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
Christian, Alex this is the cleaner way to handle AMDGPU/radeon although
if you prefer alternative methods let me know.

Review, acks and others are appreciated, since I'd like to get this
through the drm-misc tree.

Thanks
Emil

Unrelated:
The USE_AGP flag in AMDGPU should be nuked. While for radeon, one can
copy in the driver the 10-20 lines worth of agp_init/release and also
drop the flag.

Bonus points of agp_init code gets a LEGACY check alongside the USE_AGP
one.
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c |  2 +-
 drivers/gpu/drm/radeon/radeon_drv.c     |  2 +-
 include/drm/drm_drv.h                   | 10 ++++++++++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 8e1b269351e8..cfc2ef11330c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -1307,7 +1307,7 @@ amdgpu_get_crtc_scanout_position(struct drm_device *dev, unsigned int pipe,
 
 static struct drm_driver kms_driver = {
 	.driver_features =
-	    DRIVER_USE_AGP | DRIVER_ATOMIC |
+	    DRIVER_USE_AGP | DRIVER_ATOMIC | DRIVER_FORCE_AUTH |
 	    DRIVER_GEM |
 	    DRIVER_RENDER | DRIVER_MODESET | DRIVER_SYNCOBJ,
 	.load = amdgpu_driver_load_kms,
diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
index 4403e76e1ae0..5a1bfad1ad5e 100644
--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -538,7 +538,7 @@ radeon_get_crtc_scanout_position(struct drm_device *dev, unsigned int pipe,
 
 static struct drm_driver kms_driver = {
 	.driver_features =
-	    DRIVER_USE_AGP | DRIVER_GEM | DRIVER_RENDER,
+	    DRIVER_USE_AGP | DRIVER_GEM | DRIVER_RENDER | DRIVER_FORCE_AUTH,
 	.load = radeon_driver_load_kms,
 	.open = radeon_driver_open_kms,
 	.postclose = radeon_driver_postclose_kms,
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index b33f2cee2099..5fb2846396bc 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -92,6 +92,16 @@ enum drm_driver_feature {
 	 * synchronization of command submission.
 	 */
 	DRIVER_SYNCOBJ_TIMELINE         = BIT(6),
+	/**
+	 * @DRIVER_FORCE_AUTH:
+	 *
+	 * Driver mandates that DRM_AUTH is honoured, even if the same ioctl
+	 * is exposed via the render node - aka any of an "authentication" is
+	 * a fallacy.
+	 *
+	 * Used only by amdgpu and radeon. Do not use.
+	 */
+	DRIVER_FORCE_AUTH		= BIT(7),
 
 	/* IMPORTANT: Below are all the legacy flags, add new ones above. */
 
-- 
2.21.0