Messages in this thread | | | Date | Fri, 11 Nov 2022 14:30:46 +0800 | Subject | Re: [RFC PATCH v6 02/11] media: v4l2: Extend pixel formats to unify single/multi-planar handling (and more) | From | Hsia-Jun Li <> |
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On 11/11/22 13:48, Tomasz Figa wrote: > CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe. > > > On Fri, Nov 11, 2022 at 12:04 PM Hsia-Jun Li <Randy.Li@synaptics.com> wrote: >> >> >> >> On 11/11/22 01:06, Nicolas Dufresne wrote: >>> CAUTION: Email originated externally, do not click links or open attachments unless you recognize the sender and know the content is safe. >>> >>> >>> Le samedi 05 novembre 2022 à 23:19 +0800, Hsia-Jun Li a écrit : >>>>>> VIDIOC_ENUM_EXT_PIX_FMT would report NV12 and NV12M, while >>>>>> VIDIOC_ENUM_FMT >>>>>> would just report NV12M. >>>>> >>>>> If NV12 and NV12M are equivalent in Ext API, I don't see why we would >>>>> report both (unless I'm missing something, which is probably the case). >>>>> >>>>> The idea was to deprecate the M-variants one day. >>>> I was thinking the way in DRM API is better, always assuming it would >>>> always in a multiple planes. The only problem is we don't have a way to >>>> let the allocator that allocate contiguous memory for planes when we >>>> need to do that. >>> >>> Its not too late to allow this to be negotiated, but I would move this out of >>> the pixel format definition to stop the explosion of duplicate pixel formats, >>> which is a nightmare to deal with. >> I wonder whether we need to keep the pixel formats in videodev2.h >> anymore. If we would like to use the modifiers from drm_fourcc.h, why >> don't we use their pixel formats, they should be the same values of >> non-M variant pixel formats of v4l2. >> >> Let videodev2.h only maintain the those codecs or motion based >> compressed (pixel) formats. >> >> If I simplify the discussion, we want to >>> negotiate contiguity with the driver. The new FMT structure should have a >>> CONTIGUOUS flag. So if userpace sets: >>> >>> S_FMT(NV12, CONTIGUOUS) >> I wonder whether we would allow some planes being contiguous while some >> would not. For example, the graphics planes could be in a contiguous >> memory address while its compression metadata are not. >> Although that is not the case of our platform. I believe it sounds like >> reasonable case for improving the performance, two meta planes could >> resident in a different memory bank. > > I feel like this would be only useful in the MMAP mode. Looking at how > the other UAPIs are evolving, things are going towards > userspace-managed allocations, using, for example, DMA-buf heaps. I > think we should follow the trend and keep the MMAP mode just at the > same level of functionality as is today and focus on improvements and > new functionality for the DMABUF mode. > I know there are still some devices(encoder) which only have one register for storing the address of a graphics buffer. >> >> That lead to another question which I forgot whether I mention it before. >> >> There are four modifiers in DRM while we would only one in these patches. >> From the EGL >> https://urldefense.proofpoint.com/v2/url?u=https-3A__registry.khronos.org_EGL_extensions_EXT_EGL-5FEXT-5Fimage-5Fdma-5Fbuf-5Fimport-5Fmodifiers.txt&d=DwIFaQ&c=7dfBJ8cXbWjhc0BhImu8wVIoUFmBzj1s88r8EGyM0UY&r=P4xb2_7biqBxD4LGGPrSV6j-jf3C3xlR7PXU-mLTeZE&m=mCebYOAiZK6pbpH1MrZGq-ZkDW-OqORCSwsCEX9ScgdXk_yfWZFJPC5aC93CUg5F&s=rtmW_t2LYoJ6g3Y5wgyICmABu-2Npw3JCOlvUVIYH2o&e= >> >> The modifier for echo plane could be different. I wish it would be >> better to create a framebuffer being aware of which planes are graphics >> or metadata. > > What's an echo plane? > They could be DRM_FORMAT_MOD_SYNA_V4H1_128L128_COMPRESSED DRM_FORMAT_MOD_SYNA_V4H1_128L128_COMPRESSED DRM_FORMAT_MOD_SYNA_MTR DRM_FORMAT_MOD_SYNA_MTR Or DRM_FORMAT_MOD_SYNA_V4H3P8_64L4 DRM_FORMAT_MOD_SYNA_V4H3P8_64L4
in our platform. It could give a better idea on what is stored in a plane. > That said, it indeed looks like we may want to be consistent with DRM > here and allow per-plane modifiers. > >> >> I wonder whether it would be better that convincing the DRM maintainer >> adding a non vendor flag for contiguous memory allocation here(DRM >> itself don't need it). >> While whether the memory could be contiguous for these vendor pixel >> formats, it is complex vendor defined. > > Memory allocation doesn't sound to me like it is related to formats or > modifiers in any way. I agree with Nicolas that if we want to allow > the userspace to specify if the memory should be contiguous or not, > that should be a separate flag and actually I'd probably see it in > REQBUF_EXT and CREATE_BUFS_EXT, rather than as a part of the format. > I agree with that. But here is a problem, if there was a display device(DRM) that only supports contiguous planes in a frame buffer. How do we be aware of that? >> >>> >>> The driver can accepts, and return the unmodified structure, or may drop the >>> CONTIGUOUS flag, which would mean its not supported. Could be the other way >>> around too. As for allocation, if you have CONTIGUOUS flag set, userspace does >>> not have to export or map memory for each planes, as they are the same. We >>> simply need to define the offset as relative to their allocation, which I think >>> is the most sensible thing. >>> >>> Nicolas >>> >> >> -- >> Hsia-Jun(Randy) Li
-- Hsia-Jun(Randy) Li
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