On (20/02/27 13:25), Hans Verkuil wrote: [..] > > + - vb2 buffer is allocated either in consistent (it will be automatically > > vb2 -> A > > (vb2 is a kAPI term, and shouldn't be used in uAPI documentation) > > > + coherent between CPU and bus) or non-consistent memory. The latter > > CPU and bus -> the CPU and the bus > > > + can provide performance gains, for instance CPU cache sync/flush > > CPU -> the CPU > > > + operations can be avoided if the buffer is accessed by the corresponding > > + device only and CPU does not read/write to/from that buffer. However, > > CPU -> the CPU > > > + this requires extra care from the driver -- it must guarantee memory > > + consistency by issuing cache flush/sync when consistency is needed. > > cache -> a cache > > > + If this flag is set V4L2 will attempt to allocate vb2 buffer in > > vb2 -> the > > > + non-consistent memory. The flag takes effect only if the buffer is > > + used for :ref:`memory mapping <mmap>` I/O and the queue reports > > reports -> reports the OK. > > +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst > > @@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit > > - Only valid for stateless decoders. If set, then userspace can set the > > ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the > > capture buffer until the OUTPUT timestamp changes. > > + * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS`` > > + - 0x00000040 > > + - Set when the queue/buffer support memory consistency and cache > > support -> supports OK. > > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c > > @@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps) > > *caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF; > > if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF) > > *caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF; > > + if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP)) > > Just say: > > if (q->allow_cache_hints && (q->io_modes & VB2_MMAP)) OK. -ss
