Le vendredi 05 juin 2020 à 11:35 -0400, Nicolas Dufresne a écrit : > Le jeudi 04 juin 2020 à 15:53 +0200, Neil Armstrong a écrit : > > From: Maxime Jourdan <mjourdan@xxxxxxxxxxxx> > > > > Add two generic Compressed Framebuffer pixel formats to be used > > with a modifier when imported back in another subsystem like DRM/KMS. > > > > These pixel formats represents generic 8bits and 10bits compressed buffers > > with a vendor specific layout. > > > > These are aligned with the DRM_FORMAT_YUV420_8BIT and DRM_FORMAT_YUV420_10BIT > > used to describe the underlying compressed buffers used for ARM Framebuffer > > Compression. In the Amlogic case, the compression is different but the > > underlying buffer components is the same. > > > > Signed-off-by: Maxime Jourdan <mjourdan@xxxxxxxxxxxx> > > Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> > > --- > > drivers/media/v4l2-core/v4l2-ioctl.c | 2 ++ > > include/uapi/linux/videodev2.h | 9 +++++++++ > > 2 files changed, 11 insertions(+) > > > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c > > index 2322f08a98be..8f14adfd5bc5 100644 > > --- a/drivers/media/v4l2-core/v4l2-ioctl.c > > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c > > @@ -1447,6 +1447,8 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt) > > case V4L2_PIX_FMT_S5C_UYVY_JPG: descr = "S5C73MX interleaved UYVY/JPEG"; break; > > case V4L2_PIX_FMT_MT21C: descr = "Mediatek Compressed Format"; break; > > case V4L2_PIX_FMT_SUNXI_TILED_NV12: descr = "Sunxi Tiled NV12 Format"; break; > > + case V4L2_PIX_FMT_YUV420_8BIT: descr = "Compressed YUV 4:2:0 8-bit Format"; break; > > + case V4L2_PIX_FMT_YUV420_10BIT: descr = "Compressed YUV 4:2:0 10-bit Format"; break; > > When I read the DRM documentation [0], I'm reading that YUV420_8BIT > definition matches V4L2_PIX_FMT_YVU420 and V4L2_PIX_FMT_YVU420M fully. > In fact, on DRM side, to represent that format you want to expose here, > they will strictly combine this generic format (documented un- > compressed) with a modifier generated with the macro > DRM_FORMAT_MOD_ARM_AFBC(*). And only the combination represent a unique > and share-able format. [0] https://www.kernel.org/doc/html/v5.5-rc1/gpu/afbc.html > > In absence of modifier in V4L2 API, this compressed format should be > named accordingly to the compressed algorithm used (something like > FMT_YUV420_8BIT_AML_FBC). So I believe these format name cannot be > copied as-is like this, as they can only introduce more ambiguity in > the already quite hard to follow naming of pixel formats. In fact, it > is very common to see multiple different vendor compressions on the > same SoC, so I don't really believe a "generic" compressed format make > sense. To site one, the IMX8M, which got Verrisillicon/Vivante DEC400 > on the GPU, and the Hantro G2 compression format. Both will apply to > NV12 class of format so in DRM they would be NV12 + modifier, and the > combination forms the unique format. Now, in term of sharing, they must > be differiented by userspace, as support for compression/decompression > is heterogeneous (in that case the GPU does not support Hantro G2 > decompression or compression, and the VPU does not support DEC400). > > I'll remind that the modifier implementation has great value and is > much more scalable then the current V4L2 approach. There has been some > early proposal for this, maybe it's time to prioritize because this > list will starts growing with hundred or even thousands or format, > which is clearly indicated by the increase of modifier generator macro > on the DRM side. > > > default: > > if (fmt->description[0]) > > return; > > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > > index c3a1cf1c507f..90b9949acb8a 100644 > > --- a/include/uapi/linux/videodev2.h > > +++ b/include/uapi/linux/videodev2.h > > @@ -705,6 +705,15 @@ struct v4l2_pix_format { > > #define V4L2_PIX_FMT_FWHT v4l2_fourcc('F', 'W', 'H', 'T') /* Fast Walsh Hadamard Transform (vicodec) */ > > #define V4L2_PIX_FMT_FWHT_STATELESS v4l2_fourcc('S', 'F', 'W', 'H') /* Stateless FWHT (vicodec) */ > > > > +/* > > + * Compressed Luminance+Chrominance meta-formats > > + * In these formats, the component ordering is specified (Y, followed by U > > + * then V), but the exact Linear layout is undefined. > > + * These formats can only be used with a non-Linear modifier. > > + */ > > +#define V4L2_PIX_FMT_YUV420_8BIT v4l2_fourcc('Y', 'U', '0', '8') /* 1-plane YUV 4:2:0 8-bit */ > > +#define V4L2_PIX_FMT_YUV420_10BIT v4l2_fourcc('Y', 'U', '1', '0') /* 1-plane YUV 4:2:0 10-bit */ > > + > > /* Vendor-specific formats */ > > #define V4L2_PIX_FMT_CPIA1 v4l2_fourcc('C', 'P', 'I', 'A') /* cpia1 YUV */ > > #define V4L2_PIX_FMT_WNVA v4l2_fourcc('W', 'N', 'V', 'A') /* Winnov hw compress */
