On Tue, 2020-05-05 at 16:05 +0200, Tomasz Figa wrote: > On Tue, May 5, 2020 at 3:59 PM Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> wrote: > > On Tue, 2020-05-05 at 15:56 +0200, Tomasz Figa wrote: > > > Hi Ezequiel, > > > > > > On Tue, May 5, 2020 at 3:41 PM Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> wrote: > > > > The driver should only set the payload on .buf_prepare > > > > if the buffer is CAPTURE type, or if an OUTPUT buffer > > > > has a zeroed payload. > > > > > > Thanks for the patch. Just one question below. > > > > > > Where does the requirement to set OUTPUT buffer bytesused to sizeimage > > > if the original bytesused is 0 come from? > > > > > > > If I'm reading english correctly, it's here: > > > > https://www.kernel.org/doc/html/latest/media/uapi/v4l/buffer.html > > > > """ > > The number of bytes occupied by the data in the buffer. It depends on the negotiated data format and may change with each buffer for compressed > > variable size data like JPEG images. Drivers must set this field when type refers to a capture stream, applications when it refers to an output > > stream. If the application sets this to 0 for an output stream, then bytesused will be set to the size of the buffer (see the length field of this > > struct) by the driver. For multiplanar formats this field is ignored and the planes pointer is used instead. > > """ > > Okay, thanks. I wonder if this shouldn't be handled by the core, > though. Especially given that the document refers to the length field > specifically and not the sizeimage set in the format. > Yes, either core or helper, this definitely calls for a generic solution. Ezequiel
