Re: [RFC] media: Add AFBC pixel formats
From: Benjamin Gaignard
Date: Thu Apr 16 2026 - 12:32:39 EST
Le 16/04/2026 à 17:23, Nicolas Dufresne a écrit :
Le jeudi 16 avril 2026 à 14:41 +0200, Benjamin Gaignard a écrit :
Add 8-bit and 10-bit YUV420 Arm Frame Buffer Compression (AFBC)Because these format are so tied with the Graphics, I would avoid past mistakes
pixel formats.
AFBC stride and image size computation needed to be done by
specific helpers functions which are also exported to be used
by drivers.
Add documentation for each of the formats.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
---
.../userspace-api/media/v4l/pixfmt-afbc.rst | 64 +++++++++++
.../userspace-api/media/v4l/pixfmt.rst | 1 +
drivers/media/v4l2-core/v4l2-common.c | 104 ++++++++++++++++++
drivers/media/v4l2-core/v4l2-ioctl.c | 4 +
include/media/v4l2-common.h | 4 +
include/uapi/linux/videodev2.h | 6 +
6 files changed, 183 insertions(+)
create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-afbc.rst
diff --git a/Documentation/userspace-api/media/v4l/pixfmt-afbc.rst b/Documentation/userspace-api/media/v4l/pixfmt-afbc.rst
new file mode 100644
index 000000000000..2867e5d45810
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/pixfmt-afbc.rst
@@ -0,0 +1,64 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. afbc:
+
+*******************************************
+ARM Frame Buffer Compression formats (AFBC)
+*******************************************
+
+The AFBC format is a lossless compression format which can support
+up to four components. It could compress 8 bits to 64 bits per pixel.
+The internal superblock size could be:
+
+- 16x16 pixels
+
+- 32x8 pixels
+
+- 64x4 pixels.
+
+The memory layout is composed of a header block followed by payload data.
with QC formats, and up-front document their matching DRM format and modifiers.
sure, I can add a column with the matching DRM format + modifier
While its documented in ./Documentation/userspace-api/dma-buf-alloc-exchange.rst
I would still document a bit the way we calculate a stride for this formats, or
cross-reference that documentation, but being explicit for this specific format
may avoid a lot of issues.
I don't see that in dma-buf-alloc-exchange.rst if you a place where it is
documented I can add a link to it.
+AFBC FormatsFrom my accumulate knowledge, RK35xx RKVDEC produce non-split, and this one is
+============
+
+.. tabularcolumns:: |p{5.2cm}|p{1.0cm}|p{1.5cm}|p{1.9cm}|p{1.2cm}|p{1.8cm}|
+
+.. flat-table:: Overview of AFBC formats
+ :header-rows: 1
+ :stub-columns: 0
+
+ * - Identifier
+ - Code
+ - Colorspace
+ - Bits per component
+ - Superblock size
+ - Compression parameters
+ * - V4L2_PIX_FMT_AFBC_YUV420_16x16
+ - 'A168'
+ - YUV420
+ - 8 bits
+ - 16x16
+ - Sparse, Split
split. To make it easy for naming in the future, I'd rename this one.
V4L2_PIX_FMT_AFBC_YUV420_16x16_SPLIT
Or
V4L2_PIX_FMT_AFBC_YUV420_16x16_S
V4L2_PIX_FMT_AFBC_YUV420_16x16S
Other ideas, but it would be really hard to come up with a name for "not slip".
While non-sparse is very special, and not commonly used.
Let's go for SPLIT it is more readable.
+ * - V4L2_PIX_FMT_AFBC_YUV420_32x8I want to give some more thought on this, its literally by-pass
+ - 'A328'
+ - YUV420
+ - 8 bits
+ - 32x8
+ - Sparse
+ * - V4L2_PIX_FMT_AFBC_YUV420_16x16_10
+ - 'A16a'
+ - YUV420
+ - 10 bits
+ - 16x16
+ - Sparse, Split
+ * - V4L2_PIX_FMT_AFBC_YUV420_32x8_10
+ - 'A32a'
+ - YUV420
+ - 10 bits
+ - 32x8
+ - Sparse
+
+.. _V4L2-PIX-FMT-AFBC-YUV420-16x16:
+.. _V4L2-PIX-FMT-AFBC-YUV420-32x8:
+.. _V4L2-PIX-FMT-AFBC-YUV420-16x16-10:
+.. _V4L2-PIX-FMT-AFBC-YUV420-32x8-10:
diff --git a/Documentation/userspace-api/media/v4l/pixfmt.rst b/Documentation/userspace-api/media/v4l/pixfmt.rst
index 71b29267488f..c6728b91b74f 100644
--- a/Documentation/userspace-api/media/v4l/pixfmt.rst
+++ b/Documentation/userspace-api/media/v4l/pixfmt.rst
@@ -26,6 +26,7 @@ see also :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`.)
pixfmt-indexed
pixfmt-rgb
pixfmt-bayer
+ pixfmt-afbc
yuv-formats
hsv-formats
depth-formats
diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index 554c591e1113..9187cb18a4ef 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -332,6 +332,16 @@ const struct v4l2_format_info *v4l2_format_info(u32 format)
{ .format = V4L2_PIX_FMT_NV12MT_16X16, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 2, .comp_planes = 2, .bpp = { 1, 2, 0, 0 }, .bpp_div = { 1, 1, 1, 1 }, .hdiv = 2, .vdiv = 2,
.block_w = { 16, 8, 0, 0 }, .block_h = { 16, 8, 0, 0 }},
+ /* AFBC formats */
+ { .format = V4L2_PIX_FMT_AFBC_YUV420_16x16, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 1, .comp_planes = 1, .bpp = { 6, 0, 0, 0 }, .bpp_div = { 4, 1, 1, 1 }, .hdiv = 1, .vdiv = 1,
+ .block_w = { 16, 0, 0, 0 }, .block_h = { 16, 0, 0, 0 }},
+ { .format = V4L2_PIX_FMT_AFBC_YUV420_32x8, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 1, .comp_planes = 1, .bpp = { 6, 0, 0, 0 }, .bpp_div = { 4, 1, 1, 1 }, .hdiv = 1, .vdiv = 1,
+ .block_w = { 32, 0, 0, 0 }, .block_h = { 8, 0, 0, 0 }},
+ { .format = V4L2_PIX_FMT_AFBC_YUV420_16x16_10, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 1, .comp_planes = 1, .bpp = { 15, 0, 0, 0 }, .bpp_div = { 8, 1, 1, 1 }, .hdiv = 1, .vdiv = 1,
+ .block_w = { 16, 0, 0, 0 }, .block_h = { 16, 0, 0, 0 }},
+ { .format = V4L2_PIX_FMT_AFBC_YUV420_32x8_10, .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 1, .comp_planes = 1, .bpp = { 15, 0, 0, 0 }, .bpp_div = { 8, 1, 1, 1 }, .hdiv = 1, .vdiv = 1,
+ .block_w = { 32, 0, 0, 0 }, .block_h = { 8, 0, 0, 0 }},
+
/* Bayer RGB formats */
{ .format = V4L2_PIX_FMT_SBGGR8, .pixel_enc = V4L2_PIXEL_ENC_BAYER, .mem_planes = 1, .comp_planes = 1, .bpp = { 1, 0, 0, 0 }, .bpp_div = { 1, 1, 1, 1 }, .hdiv = 1, .vdiv = 1 },
{ .format = V4L2_PIX_FMT_SGBRG8, .pixel_enc = V4L2_PIXEL_ENC_BAYER, .mem_planes = 1, .comp_planes = 1, .bpp = { 1, 0, 0, 0 }, .bpp_div = { 1, 1, 1, 1 }, .hdiv = 1, .vdiv = 1 },
@@ -448,6 +458,97 @@ void v4l2_apply_frmsize_constraints(u32 *width, u32 *height,
}
EXPORT_SYMBOL_GPL(v4l2_apply_frmsize_constraints);
+size_t v4l2_pixfmt_afbc_header_size(int fourcc, int width, int height)
+{
+ int width_in_block, height_in_block;
+
+ if (!v4l2_is_format_afbc(fourcc))
+ return 0;
+
+ switch (fourcc) {
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16:
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16_10:
+ width_in_block = ALIGN(width, 16) >> 4;
+ height_in_block = ALIGN(height, 16) >> 4;
+ break;
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8_10:
+ width_in_block = ALIGN(width, 32) >> 5;
+ height_in_block = ALIGN(height, 8) >> 3;
+ break;
+ }
+
+ return ALIGN(width_in_block * 16 * height_in_block, 128);
+}
+EXPORT_SYMBOL_GPL(v4l2_pixfmt_afbc_header_size);
+
+size_t v4l2_pixfmt_afbc_payload_size(int fourcc, int width, int height)
+{
+ int width_in_block, height_in_block, block_payload_size;
+
+ if (!v4l2_is_format_afbc(fourcc))
+ return 0;
+
+ switch (fourcc) {
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16:
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16_10:
+ width_in_block = ALIGN(width, 16) >> 4;
+ height_in_block = ALIGN(height, 16) >> 4;
+ break;
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8_10:
+ width_in_block = ALIGN(width, 32) >> 5;
+ height_in_block = ALIGN(height, 8) >> 3;
+ break;
+ }
+
+ switch (fourcc) {
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8:
+ block_payload_size = 384;
+ break;
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16_10:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8_10:
+ block_payload_size = 512;
+ break;
+ }
+
+ return ALIGN(block_payload_size * width_in_block * height_in_block, 128);
+}
+EXPORT_SYMBOL_GPL(v4l2_pixfmt_afbc_payload_size);
+
+static int v4l2_fill_pixfmt_afbc(struct v4l2_pix_format_mplane *pixfmt,
+ const struct v4l2_format_info *info)
+{
+ struct v4l2_plane_pix_format *plane = &pixfmt->plane_fmt[0];
+ unsigned int width = pixfmt->width;
+ unsigned int height = pixfmt->height;
+ unsigned int aligned_width = ALIGN(width, v4l2_format_block_width(info, 0));
+ unsigned int stride = DIV_ROUND_UP(aligned_width, info->hdiv) *
+ info->bpp[0] / info->bpp_div[0];
+ size_t header_size = v4l2_pixfmt_afbc_header_size(info->format, width, height);
+ size_t payload_size = v4l2_pixfmt_afbc_payload_size(info->format, width, height);
+
+ plane->bytesperline = stride;
+ plane->sizeimage = header_size + payload_size;
v4l2_apply_frmsize_constraints(), and that I don't like much.
+Does that really need to be exported ?
+ return 0;
+}
+
+bool v4l2_is_format_afbc(int fourcc)
+{
+ switch (fourcc) {
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8:
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16_10:
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8_10:
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(v4l2_is_format_afbc);
Yes it is useful to not duplicate it in all drivers.
+Missing "split" in the descr, which will cause confusion in the future.
int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
u32 pixelformat, u32 width, u32 height)
{
@@ -464,6 +565,9 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt,
pixfmt->pixelformat = pixelformat;
pixfmt->num_planes = info->mem_planes;
+ if (v4l2_is_format_afbc(info->format))
+ return v4l2_fill_pixfmt_afbc(pixfmt, info);
+
if (info->mem_planes == 1) {
plane = &pixfmt->plane_fmt[0];
plane->bytesperline = v4l2_format_plane_stride(info, 0, width);
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index a2b650f4ec3c..016d4244c9ee 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -1387,6 +1387,10 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
case V4L2_PIX_FMT_YVU422M: descr = "Planar YVU 4:2:2 (N-C)"; break;
case V4L2_PIX_FMT_YUV444M: descr = "Planar YUV 4:4:4 (N-C)"; break;
case V4L2_PIX_FMT_YVU444M: descr = "Planar YVU 4:4:4 (N-C)"; break;
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16: descr = "AFBC 8-bit YUV420 16x16"; break;
Ok, just keep in mind that description field is limited to 32 bytes.
Benjamin
Nicolas
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8: descr = "AFBC 8-bit YUV420 32x8"; break;
+ case V4L2_PIX_FMT_AFBC_YUV420_16x16_10: descr = "AFBC 10-bit YUV420 16x16"; break;
+ case V4L2_PIX_FMT_AFBC_YUV420_32x8_10: descr = "AFBC 10-bit YUV420 32x8"; break;
case V4L2_PIX_FMT_SBGGR8: descr = "8-bit Bayer BGBG/GRGR"; break;
case V4L2_PIX_FMT_SGBRG8: descr = "8-bit Bayer GBGB/RGRG"; break;
case V4L2_PIX_FMT_SGRBG8: descr = "8-bit Bayer GRGR/BGBG"; break;
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index f8b1faced79c..d1a75e6a7d4c 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -549,6 +549,10 @@ static inline bool v4l2_is_format_bayer(const struct v4l2_format_info *f)
return f && f->pixel_enc == V4L2_PIXEL_ENC_BAYER;
}
+bool v4l2_is_format_afbc(int fourcc);
+size_t v4l2_pixfmt_afbc_header_size(int fourcc, int width, int height);
+size_t v4l2_pixfmt_afbc_payload_size(int fourcc, int width, int height);
+
const struct v4l2_format_info *v4l2_format_info(u32 format);
void v4l2_apply_frmsize_constraints(u32 *width, u32 *height,
const struct v4l2_frmsize_stepwise *frmsize);
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index eda4492e40dc..88fafadbe13c 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -698,6 +698,12 @@ struct v4l2_pix_format {
#define V4L2_PIX_FMT_NV12M_8L128 v4l2_fourcc('N', 'A', '1', '2') /* Y/CbCr 4:2:0 8x128 tiles */
#define V4L2_PIX_FMT_NV12M_10BE_8L128 v4l2_fourcc_be('N', 'T', '1', '2') /* Y/CbCr 4:2:0 10-bit 8x128 tiles */
+/* AFBC formats */
+#define V4L2_PIX_FMT_AFBC_YUV420_16x16 v4l2_fourcc('A', '1', '6', '8') /* AFBC containing 8-bit YUV420 in 16x16 blocks, sparse, split */
+#define V4L2_PIX_FMT_AFBC_YUV420_32x8 v4l2_fourcc('A', '3', '2', '8') /* AFBC containing 8-bit YUV420 in 32x8 blocks, sparse */
+#define V4L2_PIX_FMT_AFBC_YUV420_16x16_10 v4l2_fourcc('A', '1', '6', 'a') /* AFBC containing 10-bit YUV420 in 16x16 blocks, sparse, split */
+#define V4L2_PIX_FMT_AFBC_YUV420_32x8_10 v4l2_fourcc('A', '3', '2', 'a') /* AFBC containing 10-bit YUV420 in 32x8 blocks, sparse */
+
/* Bayer formats - see http://www.siliconimaging.com/RGB%20Bayer.htm */
#define V4L2_PIX_FMT_SBGGR8 v4l2_fourcc('B', 'A', '8', '1') /* 8 BGBG.. GRGR.. */
#define V4L2_PIX_FMT_SGBRG8 v4l2_fourcc('G', 'B', 'R', 'G') /* 8 GBGB.. RGRG.. */