Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751496AbdIKKzP (ORCPT ); Mon, 11 Sep 2017 06:55:15 -0400 Received: from lb2-smtp-cloud7.xs4all.net ([194.109.24.28]:42789 "EHLO lb2-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750980AbdIKKzN (ORCPT ); Mon, 11 Sep 2017 06:55:13 -0400 Subject: Re: [PATCH v3 02/15] [media] vb2: add explicit fence user API To: Gustavo Padovan , linux-media@vger.kernel.org Cc: Mauro Carvalho Chehab , Shuah Khan , linux-kernel@vger.kernel.org, Gustavo Padovan References: <20170907184226.27482-1-gustavo@padovan.org> <20170907184226.27482-3-gustavo@padovan.org> From: Hans Verkuil Message-ID: Date: Mon, 11 Sep 2017 12:55:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170907184226.27482-3-gustavo@padovan.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4wfAbZKLjCj3osOIyUMpZ+4JyyKH5iK7czRLQNLoVL1m5n3G9KYtuhoFgsn00ulAsmSuywSKuKV2plpFVrwK4WX1jCZYOjKSTcRRNEFHG82zQqa24OVjrl nzgocGbe/LEAkxO2FyzH4U2+zhoRxNht2i8WwPexosgMjPdMw6hVXKOx0CohkSHhuPTGwPMHP9vNHwLuoEDzNRwTXFjasILykelGouYIVGUVE0jGxqq6eR1b QJT5wL6qMWKm1mmWGKmwluMVBQDG7S6GFR6EsXFAmkTZtrnEHfOpM9p380hrk8KsNeFZzAjAVkiUXOgLTca6LQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5671 Lines: 143 On 09/07/2017 08:42 PM, Gustavo Padovan wrote: > From: Gustavo Padovan > > Turn the reserved2 field into fence_fd that we will use to send > an in-fence to the kernel and return an out-fence from the kernel to > userspace. > > Two new flags were added, V4L2_BUF_FLAG_IN_FENCE, that should be used > when sending a fence to the kernel to be waited on, and > V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence. > > v2: add documentation > > Signed-off-by: Gustavo Padovan > --- > Documentation/media/uapi/v4l/buffer.rst | 19 +++++++++++++++++++ > drivers/media/usb/cpia2/cpia2_v4l.c | 2 +- > drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 ++-- > drivers/media/v4l2-core/videobuf2-v4l2.c | 2 +- > include/uapi/linux/videodev2.h | 4 +++- > 5 files changed, 26 insertions(+), 5 deletions(-) > > diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst > index ae6ee73f151c..664507ad06c6 100644 > --- a/Documentation/media/uapi/v4l/buffer.rst > +++ b/Documentation/media/uapi/v4l/buffer.rst > @@ -648,6 +648,25 @@ Buffer Flags > - Start Of Exposure. The buffer timestamp has been taken when the > exposure of the frame has begun. This is only valid for the > ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` buffer type. > + * .. _`V4L2-BUF-FLAG-IN-FENCE`: > + > + - ``V4L2_BUF_FLAG_IN_FENCE`` > + - 0x00200000 > + - Ask V4L2 to wait on fence passed in ``fence_fd`` field. The buffer > + won't be queued to the driver until the fence signals. > + > + * .. _`V4L2-BUF-FLAG-OUT-FENCE`: > + > + - ``V4L2_BUF_FLAG_OUT_FENCE`` > + - 0x00400000 > + - Request a fence for the next buffer to be queued to V4L2 driver. > + The fence received back through the ``fence_fd`` field doesn't > + necessarily relate to the current buffer in the > + :ref:`VIDIOC_QBUF ` ioctl. Although, most of the time > + the fence will relate to the current buffer it can't be guaranteed. > + So to tell userspace which buffer is associated to the out_fence, > + one should listen for the ``V4L2_EVENT_BUF_QUEUED`` event that > + provide the id of the buffer when it is queued to the V4L2 driver. As mentioned in the previous patch, this flag should just signal that userspace wants to receive a BUF_QUEUED event with the out-fence for this buffer. It's up to the driver to ensure the correct ordering of the events. I'm missing documentation for the new fence_fd field. It should mention that fence_fd is ignored if the IN_FENCE isn't set. Applications will set fence_fd (aka reserved2) to 0, which should be fine as long as IN_FENCE isn't set. > > > > diff --git a/drivers/media/usb/cpia2/cpia2_v4l.c b/drivers/media/usb/cpia2/cpia2_v4l.c > index 3dedd83f0b19..6cde686bf44c 100644 > --- a/drivers/media/usb/cpia2/cpia2_v4l.c > +++ b/drivers/media/usb/cpia2/cpia2_v4l.c > @@ -948,7 +948,7 @@ static int cpia2_dqbuf(struct file *file, void *fh, struct v4l2_buffer *buf) > buf->sequence = cam->buffers[buf->index].seq; > buf->m.offset = cam->buffers[buf->index].data - cam->frame_buffer; > buf->length = cam->frame_size; > - buf->reserved2 = 0; > + buf->fence_fd = -1; > buf->reserved = 0; > memset(&buf->timecode, 0, sizeof(buf->timecode)); > > diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > index 821f2aa299ae..d624fb5df130 100644 > --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c > @@ -370,7 +370,7 @@ struct v4l2_buffer32 { > __s32 fd; > } m; > __u32 length; > - __u32 reserved2; > + __s32 fence_fd; > __u32 reserved; > }; > > @@ -533,8 +533,8 @@ static int put_v4l2_buffer32(struct v4l2_buffer *kp, struct v4l2_buffer32 __user > put_user(kp->timestamp.tv_usec, &up->timestamp.tv_usec) || > copy_to_user(&up->timecode, &kp->timecode, sizeof(struct v4l2_timecode)) || > put_user(kp->sequence, &up->sequence) || > - put_user(kp->reserved2, &up->reserved2) || > put_user(kp->reserved, &up->reserved) || > + put_user(kp->fence_fd, &up->fence_fd) || Could you move this up one line? It's easier to parse this diff if it is clear that fence_fd replaced reserved2. > put_user(kp->length, &up->length)) > return -EFAULT; > > diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c > index 0c0669976bdc..110fb45fef6f 100644 > --- a/drivers/media/v4l2-core/videobuf2-v4l2.c > +++ b/drivers/media/v4l2-core/videobuf2-v4l2.c > @@ -203,7 +203,7 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb) > b->timestamp = ns_to_timeval(vb->timestamp); > b->timecode = vbuf->timecode; > b->sequence = vbuf->sequence; > - b->reserved2 = 0; > + b->fence_fd = -1; > b->reserved = 0; > > if (q->is_multiplanar) { > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index 185d6a0acc06..e5abab9a908c 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -924,7 +924,7 @@ struct v4l2_buffer { > __s32 fd; > } m; > __u32 length; > - __u32 reserved2; > + __s32 fence_fd; > __u32 reserved; > }; > > @@ -961,6 +961,8 @@ struct v4l2_buffer { > #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE 0x00010000 > /* mem2mem encoder/decoder */ > #define V4L2_BUF_FLAG_LAST 0x00100000 > +#define V4L2_BUF_FLAG_IN_FENCE 0x00200000 > +#define V4L2_BUF_FLAG_OUT_FENCE 0x00400000 > > /** > * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor > Regards, Hans