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authorHans de Goede <hdegoede@redhat.com>2024-08-30 13:12:05 +0200
committerLaurent Pinchart <laurent.pinchart@ideasonboard.com>2024-08-30 15:15:06 +0300
commitc05e45ac7743c60a78ebee1b9e341fa5e089285d (patch)
tree3d9ca04258a7bfe54dadb46fd4a436ab35c4dc4c /src
parent9020c2eec9de5d9b5bc1016b26e714b1c0206441 (diff)
pipeline_handler: Add acquireDevice() function to mirror releaseDevice()
libcamera always keeps all /dev/video# and /dev/v4l2_subdev# nodes for a pipeline open after enumerating the camera. This is a problem for the uvcvideo pipeline handler. Keeping /dev/video# open stops the UVC USB device from being able to enter runtime-suspend causing significant unnecessary power-usage. Add a stub acquireDevice() function to the PipelineHandler class which pipeline handlers can override. The uvcvideo pipeline handler will use this to delay opening /dev/video# until the device is acquired. This is a special case because the kernel uvcvideo driver powers on the USB device as soon as /dev/video# is opened. This behavior should *not* be copied by other pipeline handlers. Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Harvey Yang <chenghaoyang@chromium.org> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Diffstat (limited to 'src')
-rw-r--r--src/libcamera/camera.cpp2
-rw-r--r--src/libcamera/pipeline_handler.cpp48
2 files changed, 41 insertions, 9 deletions
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 382a68f7..4e393f89 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -995,7 +995,7 @@ int Camera::acquire()
if (ret < 0)
return ret == -EACCES ? -EBUSY : ret;
- if (!d->pipe_->acquire()) {
+ if (!d->pipe_->acquire(this)) {
LOG(Camera, Info)
<< "Pipeline handler in use by another process";
return -EBUSY;
diff --git a/src/libcamera/pipeline_handler.cpp b/src/libcamera/pipeline_handler.cpp
index 1fc22d6a..861815cb 100644
--- a/src/libcamera/pipeline_handler.cpp
+++ b/src/libcamera/pipeline_handler.cpp
@@ -163,20 +163,24 @@ MediaDevice *PipelineHandler::acquireMediaDevice(DeviceEnumerator *enumerator,
* has already acquired it
* \sa release()
*/
-bool PipelineHandler::acquire()
+bool PipelineHandler::acquire(Camera *camera)
{
MutexLocker locker(lock_);
- if (useCount_) {
- ++useCount_;
- return true;
+ if (useCount_ == 0) {
+ for (std::shared_ptr<MediaDevice> &media : mediaDevices_) {
+ if (!media->lock()) {
+ unlockMediaDevices();
+ return false;
+ }
+ }
}
- for (std::shared_ptr<MediaDevice> &media : mediaDevices_) {
- if (!media->lock()) {
+ if (!acquireDevice(camera)) {
+ if (useCount_ == 0)
unlockMediaDevices();
- return false;
- }
+
+ return false;
}
++useCount_;
@@ -214,11 +218,39 @@ void PipelineHandler::release(Camera *camera)
}
/**
+ * \brief Acquire resources associated with this camera
+ * \param[in] camera The camera for which to acquire resources
+ *
+ * Pipeline handlers may override this in order to get resources such as opening
+ * devices and allocating buffers when a camera is acquired.
+ *
+ * This is used by the uvcvideo pipeline handler to delay opening /dev/video#
+ * until the camera is acquired to avoid excess power consumption. The delayed
+ * opening of /dev/video# is a special case because the kernel uvcvideo driver
+ * powers on the USB device as soon as /dev/video# is opened. This behavior
+ * should *not* be copied by other pipeline handlers.
+ *
+ * \return True on success, false on failure
+ * \sa releaseDevice()
+ */
+bool PipelineHandler::acquireDevice([[maybe_unused]] Camera *camera)
+{
+ return true;
+}
+
+/**
* \brief Release resources associated with this camera
* \param[in] camera The camera for which to release resources
*
* Pipeline handlers may override this in order to perform cleanup operations
* when a camera is released, such as freeing memory.
+ *
+ * This is called once for every camera that is released. If there are resources
+ * shared by multiple cameras then the pipeline handler must take care to not
+ * release them until releaseDevice() has been called for all previously
+ * acquired cameras.
+ *
+ * \sa acquireDevice()
*/
void PipelineHandler::releaseDevice([[maybe_unused]] Camera *camera)
{