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Date: Tue, 25 Oct 2022 14:55:17 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
linux-kernel@...r.kernel.org, Tomasz Figa <tfiga@...omium.org>,
linux-media@...r.kernel.org
Subject: Re: [PATCH v1 3/3] media: uvcvideo: Do power management granularly
Hi Laurent
Thanks for the review!
On Tue, 25 Oct 2022 at 14:46, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Tue, Sep 20, 2022 at 04:09:52PM +0200, Ricardo Ribalda wrote:
> > Instead of suspending/resume the USB device at open()/close(), do it
> > when the device is actually used.
> >
> > This way we can reduce the power consumption when a service is holding
> > the video device and leaving it in an idle state.
> >
> > Reviewed-by: Tomasz Figa <tfiga@...omium.org>
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> >
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index 8d5002543e2c..b9642afabd9b 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -25,6 +25,46 @@
> >
> > #include "uvcvideo.h"
> >
> > +/* ------------------------------------------------------------------------
> > + * UVC power management
> > + */
> > +
> > +static int uvc_pm_get(struct uvc_streaming *stream)
> > +{
> > + int ret = 0;
>
> No need to initialize ret to 0.
>
> > +
> > + ret = usb_autopm_get_interface(stream->dev->intf);
> > + if (ret)
> > + return ret;
> > +
> > + mutex_lock(&stream->dev->lock);
> > + if (!stream->dev->users)
> > + ret = uvc_status_start(stream->dev, GFP_KERNEL);
>
> For devices that don't have a status endpoint, we will end up calling
> uvc_status_start() and uvc_status_stop() around most ioctl calls (all
> call sites of uvc_pm_get() and uvc_pm_put() below). uvc_status_start()
> and uvc_status_stop() are no-op in that case, but conceptually I don't
> think that's very nice. Could we instead keep the status start/stop
> calls to open()/release() ?
I do not think that we can call uvc_status_start without calling
usb_autopm_get_interface()
We could add a flag on the device, and do something like:
if (!stream->dev->users && stream->dev->has_ststatus_enpoint)
ret = uvc_status_start(stream->dev, GFP_KERNEL);
But I am not sure what is cleaner...
>
> If you don't mind, I'll give this a try and post a new version of the
> patch, that should be faster than going through another review round.
>
> > + if (!ret)
> > + stream->dev->users++;
> > + mutex_unlock(&stream->dev->lock);
> > +
> > + if (ret)
> > + usb_autopm_put_interface(stream->dev->intf);
> > +
> > + return ret;
> > +}
> > +
> > +static void uvc_pm_put(struct uvc_streaming *stream)
> > +{
> > + mutex_lock(&stream->dev->lock);
> > + if (WARN_ON(!stream->dev->users)) {
> > + mutex_unlock(&stream->dev->lock);
> > + return;
> > + }
> > + stream->dev->users--;
> > + if (!stream->dev->users)
> > + uvc_status_stop(stream->dev);
> > + mutex_unlock(&stream->dev->lock);
> > +
> > + usb_autopm_put_interface(stream->dev->intf);
> > +}
> > +
> > /* ------------------------------------------------------------------------
> > * UVC ioctls
> > */
> > @@ -249,6 +289,9 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
> > * developers test their webcams with the Linux driver as well as with
> > * the Windows driver).
> > */
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > mutex_lock(&stream->mutex);
> > if (stream->dev->quirks & UVC_QUIRK_PROBE_EXTRAFIELDS)
> > probe->dwMaxVideoFrameSize =
> > @@ -257,6 +300,7 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
> > /* Probe the device. */
> > ret = uvc_probe_video(stream, probe);
> > mutex_unlock(&stream->mutex);
> > + uvc_pm_put(stream);
> > if (ret < 0)
> > return ret;
> >
> > @@ -468,7 +512,13 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream,
> > }
> >
> > /* Probe the device with the new settings. */
> > + ret = uvc_pm_get(stream);
> > + if (ret) {
> > + mutex_unlock(&stream->mutex);
> > + return ret;
> > + }
> > ret = uvc_probe_video(stream, &probe);
> > + uvc_pm_put(stream);
> > if (ret < 0) {
> > mutex_unlock(&stream->mutex);
> > return ret;
> > @@ -559,36 +609,29 @@ static int uvc_v4l2_open(struct file *file)
> > {
> > struct uvc_streaming *stream;
> > struct uvc_fh *handle;
> > - int ret = 0;
> >
> > stream = video_drvdata(file);
> > uvc_dbg(stream->dev, CALLS, "%s\n", __func__);
> >
> > - ret = usb_autopm_get_interface(stream->dev->intf);
> > - if (ret < 0)
> > - return ret;
> > -
> > /* Create the device handle. */
> > handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> > - if (handle == NULL) {
> > - usb_autopm_put_interface(stream->dev->intf);
> > + if (!handle)
> > return -ENOMEM;
> > - }
> >
> > - mutex_lock(&stream->dev->lock);
> > - if (stream->dev->users == 0) {
> > - ret = uvc_status_start(stream->dev, GFP_KERNEL);
> > - if (ret < 0) {
> > - mutex_unlock(&stream->dev->lock);
> > - usb_autopm_put_interface(stream->dev->intf);
> > + /*
> > + * If the uvc evdev exists we cannot suspend when the device
> > + * is idle. Otherwise we will miss button actions.
> > + */
> > + if (stream->dev->input) {
> > + int ret;
> > +
> > + ret = uvc_pm_get(stream);
> > + if (ret) {
> > kfree(handle);
> > return ret;
> > }
> > }
> >
> > - stream->dev->users++;
> > - mutex_unlock(&stream->dev->lock);
> > -
> > v4l2_fh_init(&handle->vfh, &stream->vdev);
> > v4l2_fh_add(&handle->vfh);
> > handle->chain = stream->chain;
> > @@ -610,6 +653,12 @@ static int uvc_v4l2_release(struct file *file)
> > if (uvc_has_privileges(handle))
> > uvc_queue_release(&stream->queue);
> >
> > + if (handle->is_streaming)
> > + uvc_pm_put(stream);
> > +
> > + if (stream->dev->input)
> > + uvc_pm_put(stream);
> > +
> > /* Release the file handle. */
> > uvc_dismiss_privileges(handle);
> > v4l2_fh_del(&handle->vfh);
> > @@ -617,12 +666,6 @@ static int uvc_v4l2_release(struct file *file)
> > kfree(handle);
> > file->private_data = NULL;
> >
> > - mutex_lock(&stream->dev->lock);
> > - if (--stream->dev->users == 0)
> > - uvc_status_stop(stream->dev);
> > - mutex_unlock(&stream->dev->lock);
> > -
> > - usb_autopm_put_interface(stream->dev->intf);
> > return 0;
> > }
> >
> > @@ -849,9 +892,17 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
> >
> > if (handle->is_streaming)
> > goto unlock;
> > +
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + goto unlock;
> > +
> > ret = uvc_queue_streamon(&stream->queue, type);
> > handle->is_streaming = !ret;
> >
> > + if (!handle->is_streaming)
> > + uvc_pm_put(stream);
> > +
> > unlock:
> > mutex_unlock(&stream->mutex);
> >
> > @@ -875,6 +926,9 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
> > ret = uvc_queue_streamoff(&stream->queue, type);
> > handle->is_streaming = !!ret;
> >
> > + if (!handle->is_streaming)
> > + uvc_pm_put(stream);
> > +
> > unlock:
> > mutex_unlock(&stream->mutex);
> >
> > @@ -928,6 +982,7 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > u8 *buf;
> > int ret;
> >
> > @@ -941,9 +996,16 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
> > if (!buf)
> > return -ENOMEM;
> >
> > + ret = uvc_pm_get(stream);
> > + if (ret) {
> > + kfree(buf);
> > + return ret;
> > + }
> > +
> > ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id,
> > chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
> > buf, 1);
> > + uvc_pm_put(stream);
> > if (!ret)
> > *input = *buf - 1;
> >
> > @@ -956,6 +1018,7 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > u8 *buf;
> > int ret;
> >
> > @@ -977,10 +1040,17 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
> > if (!buf)
> > return -ENOMEM;
> >
> > + ret = uvc_pm_get(stream);
> > + if (ret) {
> > + kfree(buf);
> > + return ret;
> > + }
> > +
> > *buf = input + 1;
> > ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
> > chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
> > buf, 1);
> > + uvc_pm_put(stream);
> > kfree(buf);
> >
> > return ret;
> > @@ -991,8 +1061,15 @@ static int uvc_ioctl_queryctrl(struct file *file, void *fh,
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > + int ret;
> >
> > - return uvc_query_v4l2_ctrl(chain, qc);
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > + ret = uvc_query_v4l2_ctrl(chain, qc);
> > + uvc_pm_put(stream);
> > + return ret;
> > }
> >
> > static int uvc_ioctl_query_ext_ctrl(struct file *file, void *fh,
> > @@ -1000,10 +1077,15 @@ static int uvc_ioctl_query_ext_ctrl(struct file *file, void *fh,
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > struct v4l2_queryctrl qc = { qec->id };
> > int ret;
> >
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > ret = uvc_query_v4l2_ctrl(chain, &qc);
> > + uvc_pm_put(stream);
> > if (ret)
> > return ret;
> >
> > @@ -1049,6 +1131,7 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > struct v4l2_ext_control *ctrl = ctrls->controls;
> > unsigned int i;
> > int ret;
> > @@ -1073,22 +1156,30 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
> > return 0;
> > }
> >
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > ret = uvc_ctrl_begin(chain);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + uvc_pm_put(stream);
> > return ret;
> > + }
> >
> > for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> > ret = uvc_ctrl_get(chain, ctrl);
> > if (ret < 0) {
> > uvc_ctrl_rollback(handle);
> > ctrls->error_idx = i;
> > - return ret;
> > + goto done;
> > }
> > }
> >
> > ctrls->error_idx = 0;
> >
> > - return uvc_ctrl_rollback(handle);
> > + ret = uvc_ctrl_rollback(handle);
> > +done:
> > + uvc_pm_put(stream);
> > + return ret;
> > }
> >
> > static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> > @@ -1097,6 +1188,7 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> > {
> > struct v4l2_ext_control *ctrl = ctrls->controls;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > unsigned int i;
> > int ret;
> >
> > @@ -1104,9 +1196,15 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> > if (ret < 0)
> > return ret;
> >
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > +
> > ret = uvc_ctrl_begin(chain);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + uvc_pm_put(stream);
> > return ret;
> > + }
> >
> > for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> > ret = uvc_ctrl_set(handle, ctrl);
> > @@ -1114,16 +1212,20 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> > uvc_ctrl_rollback(handle);
> > ctrls->error_idx = ioctl == VIDIOC_S_EXT_CTRLS ?
> > ctrls->count : i;
> > - return ret;
> > + goto done;
> > }
> > }
> >
> > ctrls->error_idx = 0;
> >
> > if (ioctl == VIDIOC_S_EXT_CTRLS)
> > - return uvc_ctrl_commit(handle, ctrls);
> > + ret = uvc_ctrl_commit(handle, ctrls);
> > else
> > - return uvc_ctrl_rollback(handle);
> > + ret = uvc_ctrl_rollback(handle);
> > +
> > +done:
> > + uvc_pm_put(stream);
> > + return ret;
> > }
> >
> > static int uvc_ioctl_s_ext_ctrls(struct file *file, void *fh,
> > @@ -1147,8 +1249,16 @@ static int uvc_ioctl_querymenu(struct file *file, void *fh,
> > {
> > struct uvc_fh *handle = fh;
> > struct uvc_video_chain *chain = handle->chain;
> > + struct uvc_streaming *stream = handle->stream;
> > + int ret;
> > +
> > + ret = uvc_pm_get(stream);
> > + if (ret)
> > + return ret;
> > + ret = uvc_query_v4l2_menu(chain, qm);
> > + uvc_pm_put(stream);
> >
> > - return uvc_query_v4l2_menu(chain, qm);
> > + return ret;
> > }
> >
> > static int uvc_ioctl_g_selection(struct file *file, void *fh,
> >
>
> --
> Regards,
>
> Laurent Pinchart
--
Ricardo Ribalda
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