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 ? > > 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`. > >
