[PATCH] media: v4l2-ctrls: add full AV1 profile validation in validate_av1_sequence()

[Pavan Bobba <opensource206@gmail.com>]

The AV1 stateless decoder API provides the control
V4L2_CID_STATELESS_AV1_SEQUENCE to pass sequence header parameters
from userspace. The current validator only checked that seq_profile
≤ 2 and that monochrome was not signaled in profile 1.

This patch completes the "TODO: PROFILES" by enforcing all
profile-specific constraints as defined by the AV1 specification
(Section 5.5.2, "Color config syntax"):

- Profile 0: 8/10-bit only, 4:2:0 subsampling, no monochrome
- Profile 1: 8/10-bit only, 4:4:4 only, no monochrome
- Profile 2: 8/10/12-bit, 4:2:0 / 4:2:2 / 4:4:4 allowed, monochrome allowed

Additionally, when the MONO_CHROME flag is set:
- subsampling_x and subsampling_y must both be 1
- separate_uv_delta_q must be 0

These checks prevent userspace from providing invalid AV1 sequence
headers that would otherwise be accepted, leading to undefined
driver or hardware behavior.

Signed-off-by: Pavan Bobba <opensource206@gmail.com>
---
 drivers/media/v4l2-core/v4l2-ctrls-core.c | 54 +++++++++++++++++++++--
 1 file changed, 50 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index 98b960775e87..3283ed04cc36 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -852,14 +852,60 @@ static int validate_av1_sequence(struct v4l2_ctrl_av1_sequence *s)
 	 V4L2_AV1_SEQUENCE_FLAG_SEPARATE_UV_DELTA_Q))
 		return -EINVAL;
 
-	if (s->seq_profile == 1 && s->flags & V4L2_AV1_SEQUENCE_FLAG_MONO_CHROME)
-		return -EINVAL;
-
 	/* reserved */
 	if (s->seq_profile > 2)
 		return -EINVAL;
 
-	/* TODO: PROFILES */
+	/* Profile-specific checks */
+	switch (s->seq_profile) {
+	case 0:
+		/* Bit depth: 8 or 10 */
+		if (s->bit_depth != 8 && s->bit_depth != 10)
+			return -EINVAL;
+
+		/* Subsampling must be 4:2:0 → x=1, y=1 */
+		if (!(s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_X) ||
+		    !(s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_Y))
+			return -EINVAL;
+		break;
+
+	case 1:
+		/* Monochrome is forbidden in profile 1 */
+		if (s->flags & V4L2_AV1_SEQUENCE_FLAG_MONO_CHROME)
+			return -EINVAL;
+
+		/* Bit depth: 8 or 10 */
+		if (s->bit_depth != 8 && s->bit_depth != 10)
+			return -EINVAL;
+
+		/* Subsampling must be 4:4:4 → x=0, y=0 */
+		if ((s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_X) ||
+		    (s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_Y))
+			return -EINVAL;
+		break;
+
+	case 2:
+		/* Bit depth: 8, 10, or 12 */
+		if (s->bit_depth != 8 && s->bit_depth != 10 &&
+		    s->bit_depth != 12)
+			return -EINVAL;
+
+		/* Subsampling: 4:2:0, 4:2:2, or 4:4:4 allowed → no extra check */
+		break;
+	}
+
+	/* If monochrome flag is set, enforce spec rules */
+	if (s->flags & V4L2_AV1_SEQUENCE_FLAG_MONO_CHROME) {
+		/* Must signal subsampling_x=1, subsampling_y=1 */
+		if (!(s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_X) ||
+		    !(s->flags & V4L2_AV1_SEQUENCE_FLAG_SUBSAMPLING_Y))
+			return -EINVAL;
+
+		/* separate_uv_delta_q must be 0 in monochrome */
+		if (s->flags & V4L2_AV1_SEQUENCE_FLAG_SEPARATE_UV_DELTA_Q)
+			return -EINVAL;
+	}
+
 	return 0;
 }
 
-- 
2.43.0