[PATCH v2] drm/gem: Check for valid formats

[Maíra Canal]

Currently, drm_gem_fb_create() doesn't check if the pixel format is
supported, which can lead to the acceptance of invalid pixel formats
e.g. the acceptance of invalid modifiers. Therefore, add a check for
valid formats on drm_gem_fb_create().

Moreover, note that this check is only valid for atomic drivers,
because, for non-atomic drivers, checking drm_any_plane_has_format() is
not possible since the format list for the primary plane is fake, and
we'd therefor reject valid formats.

Suggested-by: Thomas Zimmermann <tzimmermann at suse.de>
Signed-off-by: Maíra Canal <mcanal at igalia.com>
---

v1 -> v2: https://lore.kernel.org/dri-devel/20230103125322.855089-1-mcanal@igalia.com/T/
- Check the modifier for each pixel plane in multi-plane formats (Thomas Zimmermann).
- Use drm_dbg_kms() instead of drm_dbg() (Thomas Zimmermann).

---
 Documentation/gpu/todo.rst                   |  7 ++-----
 drivers/gpu/drm/drm_gem_framebuffer_helper.c | 13 +++++++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index 1f8a5ebe188e..68bdafa0284f 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -276,11 +276,8 @@ Various hold-ups:
 - Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb
   setup code can't be deleted.

-- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For
-  atomic drivers we could check for valid formats by calling
-  drm_plane_check_pixel_format() against all planes, and pass if any plane
-  supports the format. For non-atomic that's not possible since like the format
-  list for the primary plane is fake and we'd therefor reject valid formats.
+- Need to switch to drm_gem_fb_create(), as now drm_gem_fb_create() checks for
+  valid formats for atomic drivers.

 - Many drivers subclass drm_framebuffer, we'd need a embedding compatible
   version of the varios drm_gem_fb_create functions. Maybe called
diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index e93533b86037..92d748f8553f 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>

 #include <drm/drm_damage_helper.h>
+#include <drm/drm_drv.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem.h>
@@ -164,6 +165,18 @@ int drm_gem_fb_init_with_funcs(struct drm_device *dev,
		return -EINVAL;
	}

+	if (drm_drv_uses_atomic_modeset(dev)) {
+		for (i = 0; i < info->num_planes; i++) {
+			if (!drm_any_plane_has_format(dev, mode_cmd->pixel_format,
+						      mode_cmd->modifier[i])) {
+				drm_dbg_kms(dev,
+					    "Unsupported pixel format %p4cc / modifier 0x%llx\n",
+					    &mode_cmd->pixel_format, mode_cmd->modifier[i]);
+				return -EINVAL;
+			}
+		}
+	}
+
	for (i = 0; i < info->num_planes; i++) {
		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
--
2.38.1