linux-kernel - [PATCH v3 4/6] media: uvcvideo: Increase/decrease the PM counter per IOCTL

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Message-Id: <20250206-uvc-granpower-ng-v3-4-32d0d7b0c5d8@chromium.org>
Date: Thu, 06 Feb 2025 19:47:03 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Hans de Goede <hdegoede@...hat.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Guennadi Liakhovetski <guennadi.liakhovetski@...el.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, 
 Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v3 4/6] media: uvcvideo: Increase/decrease the PM counter
 per IOCTL

Now we call uvc_status_get/put from the device open/close. This low
level of granularity might leave the camera powered on in situations
where it is not needed.

Increase the granularity by increasing and decreasing the Power
Management counter per ioctl. There are two special cases where the
power management outlives the ioctl: async controls and streamon. Handle
those cases as well.

In a future patch, we will remove the uvc_status_get/put from open/close.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 13 +++++++++++--
 drivers/media/usb/uvc/uvc_v4l2.c | 26 +++++++++++++++++++++++---
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 4e58476d305e..97c1141a45b3 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1594,12 +1594,15 @@ static void uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
 
 		if (ctrl->handle) {
 			WARN_ON(!ctrl->handle->pending_async_ctrls);
-			if (ctrl->handle->pending_async_ctrls)
+			if (ctrl->handle->pending_async_ctrls) {
 				ctrl->handle->pending_async_ctrls--;
+				uvc_status_put(handle->chain->dev);
+			}
 		}
 
 		ctrl->handle = new_handle;
 		handle->pending_async_ctrls++;
+		uvc_status_get(handle->chain->dev);
 		return;
 	}
 
@@ -1611,6 +1614,7 @@ static void uvc_ctrl_set_handle(struct uvc_fh *handle, struct uvc_control *ctrl,
 	if (WARN_ON(!handle->pending_async_ctrls))
 		return;
 	handle->pending_async_ctrls--;
+	uvc_status_put(handle->chain->dev);
 }
 
 void uvc_ctrl_status_event(struct uvc_video_chain *chain,
@@ -2815,6 +2819,7 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
 void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
 {
 	struct uvc_entity *entity;
+	int i;
 
 	guard(mutex)(&handle->chain->ctrl_mutex);
 
@@ -2829,7 +2834,11 @@ void uvc_ctrl_cleanup_fh(struct uvc_fh *handle)
 		}
 	}
 
-	WARN_ON(handle->pending_async_ctrls);
+	if (!WARN_ON(handle->pending_async_ctrls))
+		return;
+
+	for (i = 0; i < handle->pending_async_ctrls; i++)
+		uvc_status_put(handle->stream->dev);
 }
 
 /*
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 5d4e967938af..63d1d06d3ff6 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -670,6 +670,9 @@ static int uvc_v4l2_release(struct file *file)
 	if (uvc_has_privileges(handle))
 		uvc_queue_release(&stream->queue);
 
+	if (handle->is_streaming)
+		uvc_status_put(stream->dev);
+
 	/* Release the file handle. */
 	uvc_dismiss_privileges(handle);
 	v4l2_fh_del(&handle->vfh);
@@ -832,8 +835,10 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
 		return 0;
 
 	ret = uvc_queue_streamon(&stream->queue, type);
-	if (!ret)
+	if (!ret) {
 		handle->is_streaming = true;
+		uvc_status_get(stream->dev);
+	}
 
 	return ret;
 
@@ -851,7 +856,10 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
 	guard(mutex)(&stream->mutex);
 
 	uvc_queue_streamoff(&stream->queue, type);
-	handle->is_streaming = false;
+	if (handle->is_streaming) {
+		handle->is_streaming = false;
+		uvc_status_put(stream->dev);
+	}
 
 	return 0;
 }
@@ -1388,6 +1396,8 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
 	void __user *up = compat_ptr(arg);
 	long ret;
 
+	guard(uvc_status)(handle->stream->dev);
+
 	switch (cmd) {
 	case UVCIOC_CTRL_MAP32:
 		ret = uvc_v4l2_get_xu_mapping(&karg.xmap, up);
@@ -1422,6 +1432,16 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
 }
 #endif
 
+static long uvc_v4l2_video_ioctl2(struct file *file,
+				  unsigned int cmd, unsigned long arg)
+{
+	struct uvc_fh *handle = file->private_data;
+
+	guard(uvc_status)(handle->stream->dev);
+
+	return video_ioctl2(file, cmd, arg);
+}
+
 static ssize_t uvc_v4l2_read(struct file *file, char __user *data,
 		    size_t count, loff_t *ppos)
 {
@@ -1507,7 +1527,7 @@ const struct v4l2_file_operations uvc_fops = {
 	.owner		= THIS_MODULE,
 	.open		= uvc_v4l2_open,
 	.release	= uvc_v4l2_release,
-	.unlocked_ioctl	= video_ioctl2,
+	.unlocked_ioctl	= uvc_v4l2_video_ioctl2,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl32	= uvc_v4l2_compat_ioctl32,
 #endif

-- 
2.48.1.502.g6dc24dfdaf-goog