| Message ID | 20210412110211.275791-2-tomi.valkeinen@ideasonboard.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2,1/3] media: videobuf2-v4l2.c: add vb2_queue_change_type() helper | expand |
On 12/04/2021 14:02, Tomi Valkeinen wrote: > On some platforms a video device can capture either video data or > metadata. The driver can implement vidioc functions for both video and > metadata, and use a single vb2_queue for the buffers. However, vb2_queue > requires choosing a single buffer type, which conflicts with the idea of > capturing either video or metadata. > > The buffer type of vb2_queue can be changed, but it's not obvious how > this should be done in the drivers. To help this, add a new helper > function vb2_queue_change_type() which ensures the correct checks and > documents how it can be used. > > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> > --- > drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ > include/media/videobuf2-v4l2.h | 15 +++++++++++++++ > 2 files changed, 29 insertions(+) > > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c > index 7e96f67c60ba..2988bb38ceb1 100644 > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c > @@ -939,6 +939,20 @@ void vb2_queue_release(struct vb2_queue *q) > } > EXPORT_SYMBOL_GPL(vb2_queue_release); > > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type) > +{ > + if (type == q->type) > + return 0; > + > + if (vb2_is_busy(q)) > + return -EBUSY; > + > + q->type = type; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(vb2_queue_change_type); > + > __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) > { > struct video_device *vfd = video_devdata(file); > diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h > index c203047eb834..12fa72a664cf 100644 > --- a/include/media/videobuf2-v4l2.h > +++ b/include/media/videobuf2-v4l2.h > @@ -261,6 +261,21 @@ int __must_check vb2_queue_init_name(struct vb2_queue *q, const char *name); > */ > void vb2_queue_release(struct vb2_queue *q); > > +/** > + * vb2_queue_change_type() - change the type of an inactive vb2_queue > + * @q: pointer to &struct vb2_queue with videobuf2 queue. > + * > + * This function changes the type of the vb2_queue. This is only possible > + * if the queue is not busy (i.e. no buffers have been allocated). > + * > + * vb2_queue_change_type() can be used to support multiple buffer types using > + * the same queue. The driver can implement v4l2_ioctl_ops.vidioc_reqbufs and > + * v4l2_ioctl_ops.vidioc_create_bufs functions and call vb2_queue_change_type() > + * before calling vb2_ioctl_reqbufs() or vb2_ioctl_create_bufs(), and thus > + * "lock" the buffer type until the buffers have been released. > + */ > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type); > + > /** > * vb2_poll() - implements poll userspace operation > * @q: pointer to &struct vb2_queue with videobuf2 queue. > This is missing doc for the type parameter. I have added this to my branch: @type: The type to change to (V4L2_BUF_TYPE_VIDEO_*) I'll send a v3 after I get feedback on the vivid patches. Tomi
Hi Tomi, On Mon, Apr 12, 2021 at 02:02:09PM +0300, Tomi Valkeinen wrote: > On some platforms a video device can capture either video data or > metadata. The driver can implement vidioc functions for both video and > metadata, and use a single vb2_queue for the buffers. However, vb2_queue > requires choosing a single buffer type, which conflicts with the idea of > capturing either video or metadata. > > The buffer type of vb2_queue can be changed, but it's not obvious how > this should be done in the drivers. To help this, add a new helper > function vb2_queue_change_type() which ensures the correct checks and > documents how it can be used. > > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> > --- > drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ > include/media/videobuf2-v4l2.h | 15 +++++++++++++++ > 2 files changed, 29 insertions(+) > Good to see you contributing to the media subsystem. Not sure if you still remember me from the Common Display Framework discussions. ;) Anyway, thanks for the patch. I think the code itself is okay, but I'm wondering why the driver couldn't just have two queues, one for each type? Best regards, Tomasz > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c > index 7e96f67c60ba..2988bb38ceb1 100644 > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c > @@ -939,6 +939,20 @@ void vb2_queue_release(struct vb2_queue *q) > } > EXPORT_SYMBOL_GPL(vb2_queue_release); > > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type) > +{ > + if (type == q->type) > + return 0; > + > + if (vb2_is_busy(q)) > + return -EBUSY; > + > + q->type = type; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(vb2_queue_change_type); > + > __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) > { > struct video_device *vfd = video_devdata(file); > diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h > index c203047eb834..12fa72a664cf 100644 > --- a/include/media/videobuf2-v4l2.h > +++ b/include/media/videobuf2-v4l2.h > @@ -261,6 +261,21 @@ int __must_check vb2_queue_init_name(struct vb2_queue *q, const char *name); > */ > void vb2_queue_release(struct vb2_queue *q); > > +/** > + * vb2_queue_change_type() - change the type of an inactive vb2_queue > + * @q: pointer to &struct vb2_queue with videobuf2 queue. > + * > + * This function changes the type of the vb2_queue. This is only possible > + * if the queue is not busy (i.e. no buffers have been allocated). > + * > + * vb2_queue_change_type() can be used to support multiple buffer types using > + * the same queue. The driver can implement v4l2_ioctl_ops.vidioc_reqbufs and > + * v4l2_ioctl_ops.vidioc_create_bufs functions and call vb2_queue_change_type() > + * before calling vb2_ioctl_reqbufs() or vb2_ioctl_create_bufs(), and thus > + * "lock" the buffer type until the buffers have been released. > + */ > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type); > + > /** > * vb2_poll() - implements poll userspace operation > * @q: pointer to &struct vb2_queue with videobuf2 queue. > -- > 2.25.1 >
Hi Tomasz, On 04/06/2021 14:13, Tomasz Figa wrote: > Hi Tomi, > > On Mon, Apr 12, 2021 at 02:02:09PM +0300, Tomi Valkeinen wrote: >> On some platforms a video device can capture either video data or >> metadata. The driver can implement vidioc functions for both video and >> metadata, and use a single vb2_queue for the buffers. However, vb2_queue >> requires choosing a single buffer type, which conflicts with the idea of >> capturing either video or metadata. >> >> The buffer type of vb2_queue can be changed, but it's not obvious how >> this should be done in the drivers. To help this, add a new helper >> function vb2_queue_change_type() which ensures the correct checks and >> documents how it can be used. >> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> >> --- >> drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ >> include/media/videobuf2-v4l2.h | 15 +++++++++++++++ >> 2 files changed, 29 insertions(+) >> > > Good to see you contributing to the media subsystem. Not sure if you > still remember me from the Common Display Framework discussions. ;) I barely remember CDF... ;) > Anyway, thanks for the patch. I think the code itself is okay, but I'm > wondering why the driver couldn't just have two queues, one for each > type? There was an email thread about this: https://www.spinics.net/lists/linux-media/msg189144.html struct video_device has 'queue' field, so if you have two queues, you'd need to change the vd->queue based on the format. Possibly that could be a solution too (and, if I recall right, that's what I initially tried as a quick hack). Changing the whole queue sounds riskier than changing just the type. Tomi
Hi Tomi, Thank you for the patch. On Mon, Apr 12, 2021 at 02:02:09PM +0300, Tomi Valkeinen wrote: > On some platforms a video device can capture either video data or > metadata. The driver can implement vidioc functions for both video and > metadata, and use a single vb2_queue for the buffers. However, vb2_queue > requires choosing a single buffer type, which conflicts with the idea of > capturing either video or metadata. > > The buffer type of vb2_queue can be changed, but it's not obvious how > this should be done in the drivers. To help this, add a new helper > function vb2_queue_change_type() which ensures the correct checks and > documents how it can be used. > > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> > --- > drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ > include/media/videobuf2-v4l2.h | 15 +++++++++++++++ > 2 files changed, 29 insertions(+) > > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c > index 7e96f67c60ba..2988bb38ceb1 100644 > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c > @@ -939,6 +939,20 @@ void vb2_queue_release(struct vb2_queue *q) > } > EXPORT_SYMBOL_GPL(vb2_queue_release); > > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type) > +{ > + if (type == q->type) > + return 0; > + > + if (vb2_is_busy(q)) > + return -EBUSY; > + > + q->type = type; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(vb2_queue_change_type); > + > __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) > { > struct video_device *vfd = video_devdata(file); > diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h > index c203047eb834..12fa72a664cf 100644 > --- a/include/media/videobuf2-v4l2.h > +++ b/include/media/videobuf2-v4l2.h > @@ -261,6 +261,21 @@ int __must_check vb2_queue_init_name(struct vb2_queue *q, const char *name); > */ > void vb2_queue_release(struct vb2_queue *q); > > +/** > + * vb2_queue_change_type() - change the type of an inactive vb2_queue > + * @q: pointer to &struct vb2_queue with videobuf2 queue. > + * > + * This function changes the type of the vb2_queue. This is only possible > + * if the queue is not busy (i.e. no buffers have been allocated). > + * > + * vb2_queue_change_type() can be used to support multiple buffer types using > + * the same queue. The driver can implement v4l2_ioctl_ops.vidioc_reqbufs and I think this should be &v4l2_ioctl_ops.vidioc_reqbufs() (same below) to generate links properly. > + * v4l2_ioctl_ops.vidioc_create_bufs functions and call vb2_queue_change_type() > + * before calling vb2_ioctl_reqbufs() or vb2_ioctl_create_bufs(), and thus > + * "lock" the buffer type until the buffers have been released. It would be nice if selection of the type could be moved to the .queue_setup() operation, but that's more difficult and would require rework of the reqbufs and create_bufs implementations that may be tricky. Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > + */ > +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type); > + > /** > * vb2_poll() - implements poll userspace operation > * @q: pointer to &struct vb2_queue with videobuf2 queue. -- Regards, Laurent Pinchart
On Fri, Jun 4, 2021 at 11:09 PM Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> wrote: > > Hi Tomasz, > > On 04/06/2021 14:13, Tomasz Figa wrote: > > Hi Tomi, > > > > On Mon, Apr 12, 2021 at 02:02:09PM +0300, Tomi Valkeinen wrote: > >> On some platforms a video device can capture either video data or > >> metadata. The driver can implement vidioc functions for both video and > >> metadata, and use a single vb2_queue for the buffers. However, vb2_queue > >> requires choosing a single buffer type, which conflicts with the idea of > >> capturing either video or metadata. > >> > >> The buffer type of vb2_queue can be changed, but it's not obvious how > >> this should be done in the drivers. To help this, add a new helper > >> function vb2_queue_change_type() which ensures the correct checks and > >> documents how it can be used. > >> > >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> > >> --- > >> drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ > >> include/media/videobuf2-v4l2.h | 15 +++++++++++++++ > >> 2 files changed, 29 insertions(+) > >> > > > > Good to see you contributing to the media subsystem. Not sure if you > > still remember me from the Common Display Framework discussions. ;) > > I barely remember CDF... ;) > > > Anyway, thanks for the patch. I think the code itself is okay, but I'm > > wondering why the driver couldn't just have two queues, one for each > > type? > > There was an email thread about this: > > https://www.spinics.net/lists/linux-media/msg189144.html > > struct video_device has 'queue' field, so if you have two queues, you'd > need to change the vd->queue based on the format. Possibly that could be > a solution too (and, if I recall right, that's what I initially tried as > a quick hack). Changing the whole queue sounds riskier than changing > just the type. Okay, I see. Thanks for the pointer. Generally I'm fine with this, although it's worth noting that it's not true that one video_device can only have 1 queue. See the numerous mem-to-mem devices, which use two queues simultaneously. Anyway, Acked-by: Tomasz Figa <tfiga@chromium.org> Best regards, Tomasz
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c index 7e96f67c60ba..2988bb38ceb1 100644 --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c @@ -939,6 +939,20 @@ void vb2_queue_release(struct vb2_queue *q) } EXPORT_SYMBOL_GPL(vb2_queue_release); +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type) +{ + if (type == q->type) + return 0; + + if (vb2_is_busy(q)) + return -EBUSY; + + q->type = type; + + return 0; +} +EXPORT_SYMBOL_GPL(vb2_queue_change_type); + __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) { struct video_device *vfd = video_devdata(file); diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h index c203047eb834..12fa72a664cf 100644 --- a/include/media/videobuf2-v4l2.h +++ b/include/media/videobuf2-v4l2.h @@ -261,6 +261,21 @@ int __must_check vb2_queue_init_name(struct vb2_queue *q, const char *name); */ void vb2_queue_release(struct vb2_queue *q); +/** + * vb2_queue_change_type() - change the type of an inactive vb2_queue + * @q: pointer to &struct vb2_queue with videobuf2 queue. + * + * This function changes the type of the vb2_queue. This is only possible + * if the queue is not busy (i.e. no buffers have been allocated). + * + * vb2_queue_change_type() can be used to support multiple buffer types using + * the same queue. The driver can implement v4l2_ioctl_ops.vidioc_reqbufs and + * v4l2_ioctl_ops.vidioc_create_bufs functions and call vb2_queue_change_type() + * before calling vb2_ioctl_reqbufs() or vb2_ioctl_create_bufs(), and thus + * "lock" the buffer type until the buffers have been released. + */ +int vb2_queue_change_type(struct vb2_queue *q, unsigned int type); + /** * vb2_poll() - implements poll userspace operation * @q: pointer to &struct vb2_queue with videobuf2 queue.
On some platforms a video device can capture either video data or metadata. The driver can implement vidioc functions for both video and metadata, and use a single vb2_queue for the buffers. However, vb2_queue requires choosing a single buffer type, which conflicts with the idea of capturing either video or metadata. The buffer type of vb2_queue can be changed, but it's not obvious how this should be done in the drivers. To help this, add a new helper function vb2_queue_change_type() which ensures the correct checks and documents how it can be used. Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> --- drivers/media/common/videobuf2/videobuf2-v4l2.c | 14 ++++++++++++++ include/media/videobuf2-v4l2.h | 15 +++++++++++++++ 2 files changed, 29 insertions(+)