[PATCH v5 1/5] libcamera: v4l2_device: add frame start event helpers

[Barnabás Pőcze]

Hi


2025. 03. 02. 0:17 keltezéssel, Kieran Bingham írta:
> Quoting Stanislaw Gruszka (2025-02-25 16:41:12)
>> Add helper to check if frame start event are supported by subdevice.
>> Since kernel does not have interface to query supported events
>> use subscribe interface.
>>
>> Additionally add helper for checking if the event enabled.
>> Will be needed later to proper code flow if enabling the event
>> fail for some reason.
>>
>> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com> # v3
>> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka at linux.intel.com>
>> ---
>>   include/libcamera/internal/v4l2_device.h |  1 +
>>   src/libcamera/v4l2_device.cpp            | 19 +++++++++++++++++++
>>   2 files changed, 20 insertions(+)
>>
>> diff --git a/include/libcamera/internal/v4l2_device.h b/include/libcamera/internal/v4l2_device.h
>> index affe52c2..a647c96a 100644
>> --- a/include/libcamera/internal/v4l2_device.h
>> +++ b/include/libcamera/internal/v4l2_device.h
>> @@ -45,6 +45,7 @@ public:
>>          const std::string &deviceNode() const { return deviceNode_; }
>>          std::string devicePath() const;
>>
>> +       bool supportsFrameStartEvent();
>>          int setFrameStartEnabled(bool enable);
>>          Signal<uint32_t> frameStart;
>>
>> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
>> index 2f65a43a..23c7d1ef 100644
>> --- a/src/libcamera/v4l2_device.cpp
>> +++ b/src/libcamera/v4l2_device.cpp
>> @@ -449,6 +449,25 @@ std::string V4L2Device::devicePath() const
>>          return path;
>>   }
>>
>> +/**
>> + * \brief Check if frame start event is supported
>> + * \return True if frame start event is supported, false otherwise
>> + */
>> +
>> +bool V4L2Device::supportsFrameStartEvent()
>> +{
>> +       struct v4l2_event_subscription event {
>> +       };
> 
> Curiously my local clang-format is trying to make this one line, but the
> CI doesn't report anything here.
> 
> So I'll leave it as it is ;-)
> 
> Aha, and I've already got a tag on here so ... to the next one.

Mine also does not like it (clang-format version 19.1.7):

$ ./utils/checkstyle.py HEAD~5..
----------------------------------------------------------------------------------------------
e7ff7c085a79342e933ae378e710e98a52f1799d libcamera: v4l2_device: add frame start event helpers
----------------------------------------------------------------------------------------------
--- src/libcamera/v4l2_device.cpp
+++ src/libcamera/v4l2_device.cpp
@@ -456,8 +456,7 @@
  
  bool V4L2Device::supportsFrameStartEvent()
  {
-	struct v4l2_event_subscription event {
-	};
+	struct v4l2_event_subscription event{};
  	event.type = V4L2_EVENT_FRAME_SYNC;
  
  	int ret = ioctl(VIDIOC_SUBSCRIBE_EVENT, &event);
---
1 potential issue detected, please review

---------------------------------------------------------------------------------------------------
2f377f31a4b7f9993c765208ece1c20430def83f pipeline: simple: Use proper device for frame start events
---------------------------------------------------------------------------------------------------
No issue detected

----------------------------------------------------------------------------------------------------
80571431a1d6d3cd9b2540d6f85e247b442a5036 pipeline: simple: Connect and disconnect start frame events
----------------------------------------------------------------------------------------------------
No issue detected

--------------------------------------------------------------------------------------
56169675ca7acee83648c1fa04278da3f446e0c6 pipeline: simple: Do not apply controls twice
--------------------------------------------------------------------------------------
No issue detected

----------------------------------------------------------------------------------------------------
005bd327d8ab71172ee7b8c61dac826e78af520c pipeline: simple: Create DelayedControls instance once only
----------------------------------------------------------------------------------------------------
No issue detected


Regards,
Barnabás Pőcze

> 
> --
> Kieran
> 
>> +       event.type = V4L2_EVENT_FRAME_SYNC;
>> +
>> +       int ret = ioctl(VIDIOC_SUBSCRIBE_EVENT, &event);
>> +       if (ret)
>> +               return false;
>> +
>> +       ioctl(VIDIOC_UNSUBSCRIBE_EVENT, &event);
>> +       return true;
>> +}
>> +
>>   /**
>>    * \brief Enable or disable frame start event notification
>>    * \param[in] enable True to enable frame start events, false to disable them
>> --
>> 2.43.0
>>