[PATCH wayland-protocols v3] linux-dmabuf: add immediate dmabuf import path

Mon Feb 6 15:33:18 UTC 2017

On Mon, 6 Feb 2017 13:33:43 +0530
Varad Gautam <varadgautam at gmail.com> wrote:

> Hi Pekka,
> 
> On Fri, Feb 3, 2017 at 8:39 PM, Pekka Paalanen
> <pekka.paalanen at collabora.co.uk> wrote:
> > On Tue, 31 Jan 2017 18:41:52 +0530
> > Varad Gautam <varadgautam at gmail.com> wrote:
> >  
> >> From: Varad Gautam <varad.gautam at collabora.com>
> >>
> >> provide a mechanism that allows clients to import the added dmabufs
> >> and immediately use the newly created wl_buffers without waiting on
> >> an event. this is useful to clients that are sure of their import
> >> request succeeding, and wish to avoid the wl_buffer communication
> >> roundtrip.
> >>
> >> bump zwp_linux_dmabuf_v1, zwp_linux_buffer_params_v1 interface
> >> versions.
> >>
> >> v2: specify using incorrectly imported dmabufs as undefined behavior
> >> instead of sending success/failure events. (pq, daniels)
> >> v3: preserve the optional protocol error added in v2 and explicitly
> >> state the outcome of import success or failure (pq)
> >>
> >> Signed-off-by: Varad Gautam <varad.gautam at collabora.com>
> >> ---
> >>  unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml | 58 +++++++++++++++++++---
> >>  1 file changed, 51 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> >> index ed2c4bb..ddb49cc 100644
> >> --- a/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> >> +++ b/unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml
> >> @@ -24,13 +24,13 @@
> >>      DEALINGS IN THE SOFTWARE.
> >>    </copyright>
> >>
> >> -  <interface name="zwp_linux_dmabuf_v1" version="1">
> >> +  <interface name="zwp_linux_dmabuf_v1" version="2">
> >>      <description summary="factory for creating dmabuf-based wl_buffers">
> >>        Following the interfaces from:
> >>        https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
> >>        and the Linux DRM sub-system's AddFb2 ioctl.
> >>
> >> -      This interface offers a way to create generic dmabuf-based
> >> +      This interface offers ways to create generic dmabuf-based
> >>        wl_buffers. Immediately after a client binds to this interface,
> >>        the set of supported formats is sent with 'format' events.
> >>
> >> @@ -56,10 +56,23 @@
> >>        To create a wl_buffer from one or more dmabufs, a client creates a
> >>        zwp_linux_dmabuf_params_v1 object with a zwp_linux_dmabuf_v1.create_params
> >>        request. All planes required by the intended format are added with
> >> -      the 'add' request. Finally, a 'create' request is issued. The server
> >> -      will reply with either a 'created' event which provides the final
> >> -      wl_buffer or a 'failed' event saying that it cannot use the dmabufs
> >> -      provided.
> >> +      the 'add' request. Finally, a 'create' or 'create_immed' request is
> >> +      issued, which has the following outcome depending on the import success.
> >> +
> >> +      The 'create' request,
> >> +      - on success, triggers a 'created' event which provides the final
> >> +        wl_buffer to the client.
> >> +      - on failure, triggers a 'failed' event to convey that the server
> >> +        cannot use the dmabufs received from the client.
> >> +
> >> +      For the 'create_immed' request,
> >> +      - on success, the server immediately imports the added dmabufs to
> >> +        create a wl_buffer. No event is sent from the server in this case.
> >> +      - on failure, the server can choose to either:
> >> +        - terminate the client by raising a fatal error.
> >> +        - create an invalid wl_buffer handle and send a 'failed' event to
> >> +          the client. The result of using this invalid wl_buffer in the
> >> +          client is left implementation-defined by the protocol.  
> >
> > Hi,
> >
> > I would phrase the latter as:
> >
> >         - Mark the wl_buffer as failed and send a 'failed' event to the
> >           client. If the client uses a failed wl_buffer as an argument
> >           to any request, the behaviour is compositor
> >           implementation-defined.
> >  
> 
> ack, will fix.
> 
> >>
> >>        Warning! The protocol described in this file is experimental and
> >>        backward incompatible changes may be made. Backward compatible changes
> >> @@ -105,7 +118,7 @@
> >>      </event>
> >>    </interface>
> >>
> >> -  <interface name="zwp_linux_buffer_params_v1" version="1">
> >> +  <interface name="zwp_linux_buffer_params_v1" version="2">
> >>      <description summary="parameters for creating a dmabuf-based wl_buffer">
> >>        This temporary object is a collection of dmabufs and other
> >>        parameters that together form a single logical buffer. The temporary
> >> @@ -138,6 +151,9 @@
> >>               summary="invalid width or height"/>
> >>        <entry name="out_of_bounds" value="6"
> >>               summary="offset + stride * height goes out of dmabuf bounds"/>
> >> +      <entry name="invalid_wl_buffer" value="7"
> >> +             summary="invalid wl_buffer resulted from importing dmabufs from
> >> +               the given buffer_params"/>  
> >
> > I might have called it "import_failure". Not a big deal.  
> >>      </enum>
> >>
> >>      <request name="destroy" type="destructor">
> >> @@ -269,6 +285,34 @@
> >>          zlinux_buffer_params object.
> >>        </description>
> >>      </event>
> >> +
> >> +    <request name="create_immed" since="2">
> >> +      <description summary="immediately create a wl_buffer from the given
> >> +                     dmabufs">
> >> +        This asks for immediate creation of a wl_buffer by importing the
> >> +        added dmabufs.
> >> +
> >> +        In case of import success, no event is sent from the server, and the
> >> +        wl_buffer is ready to be used by the client.
> >> +
> >> +        Upon import failure, either of the following may happen, as seen fit
> >> +        by the implementation:
> >> +        - the client is terminated with a fatal protocol error.  
> >
> > Could mention the error code here, since there is one specifically for
> > this case.  
> 
> we may still have the immed import path failing with any of the already
> existing error codes besides invalid_wl_buffer, eg. due to bad buffer params.
> 
> This particular token would only show up when the reason for failure doesn't
> fit any of the existing codes, possibly when the compositor made an attempt to
> import after validating the params, but ended up with an invalid
> wl_buffer instead.

Hi,

oh indeed!

I think the new error code could be explained a bit better though. It
is an import failure that can only happen with 'create_immed' request
and the exact reason for the failure is unknown, maybe platform
specific.

The new error code cannot happen with 'create' request, because in that
case the 'failed' event gets sent. That's actually already documented,
because 'create' lists the error codes it may raise. I am in favour of
listing explicitly which fatal errors can be raised by a request.

Thanks,
pq

> >  
> >> +        - the server creates an invalid wl_buffer and sends a 'failed' event
> >> +          to the client. The result of using this invalid wl_buffer created
> >> +          by the server is implementation defined.  
> >
> > The same rephrasing as above.  
> 
> ack.
> 
> >  
> >> +
> >> +        This takes the same arguments as a 'create' request, and obeys the
> >> +        same restrictions.
> >> +      </description>
> >> +      <arg name="buffer_id" type="new_id" interface="wl_buffer"
> >> +           summary="id for the newly created wl_buffer"/>
> >> +      <arg name="width" type="int" summary="base plane width in pixels"/>
> >> +      <arg name="height" type="int" summary="base plane height in pixels"/>
> >> +      <arg name="format" type="uint" summary="DRM_FORMAT code"/>
> >> +      <arg name="flags" type="uint" summary="see enum flags"/>
> >> +    </request>
> >> +
> >>    </interface>
> >>
> >>  </protocol>  
> >
> > Looking good, just a couple cosmetics I'd wish to see adjusted, but
> > regardless:
> > Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>  
> 
> Thanks for looking at this!
> Varad
> 
> >
> > Thanks,
> > pq  
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