On 5/14/19 2:19 PM, Nicolas Dufresne wrote: > Le mardi 14 mai 2019 à 10:54 +0200, Hans Verkuil a écrit : >> Hi Stanimir, >> >> On 4/12/19 5:59 PM, Stanimir Varbanov wrote: >>> This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage >>> field description to allow v4l clients to set bigger image size >>> in case of variable length compressed data. >> >> I've been reconsidering this change. The sizeimage value in the format >> is the minimum size a buffer should have in order to store the data of >> an image of the width and height as described in the format. > > Should this read as the minimum size for the specific (returned by > driver) width/height/bytesperline ? Yes. Although for compressed formats the bytesperline value plays no role of course. Regards, Hans > >> >> But there is nothing that prevents userspace from calling VIDIOC_CREATEBUFS >> instead of VIDIOC_REQBUFS to allocate larger buffers. >> >> So do we really need this change? >> >> The more I think about this, the more uncomfortable I become with this change. >> >> Regards, >> >> Hans >> >>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@xxxxxxxxxx> >>> --- >>> Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst | 13 ++++++++++++- >>> Documentation/media/uapi/v4l/pixfmt-v4l2.rst | 11 ++++++++++- >>> 2 files changed, 22 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst >>> index 5688c816e334..005428a8121e 100644 >>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst >>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst >>> @@ -31,7 +31,18 @@ describing all planes of that format. >>> >>> * - __u32 >>> - ``sizeimage`` >>> - - Maximum size in bytes required for image data in this plane. >>> + - Maximum size in bytes required for image data in this plane, >>> + set by the driver. When the image consists of variable length >>> + compressed data this is the number of bytes required by the >>> + codec to support the worst-case compression scenario. >>> + >>> + For uncompressed images the driver will set the value. For >>> + variable length compressed data clients are allowed to set >>> + the sizeimage field, but the driver may ignore it and set the >>> + value itself, or it may modify the provided value based on >>> + alignment requirements or minimum/maximum size requirements. >>> + If the client wants to leave this to the driver, then it should >>> + set sizeimage to 0. >>> * - __u32 >>> - ``bytesperline`` >>> - Distance in bytes between the leftmost pixels in two adjacent >>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst >>> index 71eebfc6d853..0f7771151db9 100644 >>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst >>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst >>> @@ -89,7 +89,16 @@ Single-planar format structure >>> - Size in bytes of the buffer to hold a complete image, set by the >>> driver. Usually this is ``bytesperline`` times ``height``. When >>> the image consists of variable length compressed data this is the >>> - maximum number of bytes required to hold an image. >>> + number of bytes required by the codec to support the worst-case >>> + compression scenario. >>> + >>> + For uncompressed images the driver will set the value. For >>> + variable length compressed data clients are allowed to set >>> + the sizeimage field, but the driver may ignore it and set the >>> + value itself, or it may modify the provided value based on >>> + alignment requirements or minimum/maximum size requirements. >>> + If the client wants to leave this to the driver, then it should >>> + set sizeimage to 0. >>> * - __u32 >>> - ``colorspace`` >>> - Image colorspace, from enum :c:type:`v4l2_colorspace`. >>> >
