On Wed, May 22, 2024 at 02:16:22PM +0300, Laurent Pinchart wrote: > Hi Jefrey, > > Thank you for the patch. > > On Thu, May 16, 2024 at 08:20:42PM +0800, Yunfei Dong wrote: > > From: Jeffrey Kardatzke <jkardatzke@xxxxxxxxxx> > > > > Adds documentation for V4L2_MEMORY_FLAG_RESTRICTED. > > > > Signed-off-by: Jeffrey Kardatzke <jkardatzke@xxxxxxxxxx> > > Signed-off-by: Yunfei Dong <yunfei.dong@xxxxxxxxxxxx> > > --- > > Documentation/userspace-api/media/v4l/buffer.rst | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst > > index 52bbee81c080..807e43bfed2b 100644 > > --- a/Documentation/userspace-api/media/v4l/buffer.rst > > +++ b/Documentation/userspace-api/media/v4l/buffer.rst > > @@ -696,7 +696,7 @@ enum v4l2_memory > > > > .. _memory-flags: > > > > -Memory Consistency Flags > > +Memory Flags > > ------------------------ > > > > .. raw:: latex > > @@ -728,6 +728,14 @@ Memory Consistency Flags > > only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the > > queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS > > <V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability. > > + * .. _`V4L2-MEMORY-FLAG-RESTRICTED`: > > + > > + - ``V4L2_MEMORY_FLAG_RESTRICTED`` > > + - 0x00000002 > > + - The queued buffers are expected to be in restricted memory. If not, an > > + error will be returned. This flag can only be used with ``V4L2_MEMORY_DMABUF``. > > + Typically restricted buffers are allocated using a restricted dma-heap. This flag > > + can only be specified if the ``V4L2_BUF_CAP_SUPPORTS_RESTRICTED_MEM`` is set. > > Why is this flag needed ? Given that the usage model requires the V4L2 > device to be a dma buf importer, why would userspace set the > V4L2_BUF_CAP_SUPPORTS_RESTRICTED_MEM flag and pass a non-restricted > buffer to the device ? Given that the flag is specified at REQBUF / CREATE_BUFS time, it's actually useful to tell the driver the queue is operating in restricted (aka secure) mode. I suppose we could handle that at the time of a first QBUF, but that would make the driver initialization and validation quite a bit of pain. So I'd say that the design being proposed here makes things simpler and more clear, even if it doesn't add any extra functionality. > > The V4L2_BUF_CAP_SUPPORTS_RESTRICTED_MEM flag also needs to be > documented in the relevant section, I don't think that's done in this > series. > +1 Best regards, Tomasz > > > > .. raw:: latex > > > > -- > Regards, > > Laurent Pinchart
