[libcamera-devel] [PATCH v2 1/6] libcamera: v4l2_device: Add setFd()

[Kieran Bingham]

Hi Laurent,

On 12/08/2019 08:20, Kieran Bingham wrote:
> 
> 
> On 09/08/2019 23:48, Laurent Pinchart wrote:
>> Hi Kieran,
>>
>> Thank you for the patch.
>>
>> On Fri, Aug 09, 2019 at 04:04:54PM +0100, Kieran Bingham wrote:
>>> Provide a means for V4L2 device instances to set the fd_ explicitly.
>>> This allows for V4L2Devices to operate when they must use an external
>>> open() call.
>>>
>>> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>>> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>>> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
>>> ---
>>>  src/libcamera/include/v4l2_device.h |  1 +
>>>  src/libcamera/v4l2_device.cpp       | 26 ++++++++++++++++++++++++++
>>>  2 files changed, 27 insertions(+)
>>>
>>> diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
>>> index e7e9829cb05f..7c3af5f6ebe0 100644
>>> --- a/src/libcamera/include/v4l2_device.h
>>> +++ b/src/libcamera/include/v4l2_device.h
>>> @@ -39,6 +39,7 @@ protected:
>>>  	int ioctl(unsigned long request, void *argp);
>>>  
>>>  	int fd() { return fd_; }
>>> +	int setFd(int fd);
>>>  
>>>  private:
>>>  	void listControls();
>>> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
>>> index 9a00566a532b..ba4c0d725752 100644
>>> --- a/src/libcamera/v4l2_device.cpp
>>> +++ b/src/libcamera/v4l2_device.cpp
>>> @@ -308,6 +308,32 @@ int V4L2Device::ioctl(unsigned long request, void *argp)
>>>   * \return The V4L2 device file descriptor, -1 if the device node is not open
>>>   */
>>>  
>>> +/**
>>> + * \brief Set the file descriptor of a V4L2 device
>>> + * \param[in] fd The file descriptor handle
>>> + *
>>> + * This method allows a device to provide an already opened file descriptor
>>> + * referring to the V4L2 device node, instead of opening it with open(). This
>>> + * can be used for V4L2 M2M devices where a single video device node is used for
>>> + * both the output and capture devices, or when receiving an open file
>>> + * descriptor in a context that doesn't have permission to open the device node
>>> + * itself.
>>> + *
>>> + * This method and the open() method are mutually exclusive, only one of the two
>>> + * shall be used for a V4L2Device instance.
>>> + *
>>> + * \return 0 on success or a negative error code otherwise
>>> + */
>>> +int V4L2Device::setFd(int fd)
>>> +{
>>> +	if (fd_ != -1)
>>> +		return -1;
>>
>> Just one more comment, would -EBUSY be more appropriate ?
> 
> Yes, probably. I'll update.

This should really be:

	if (isOpen())
		return -EBUSY;

to match the open() call.

Then I think setFd() should move up in the file to between open() and
close() too.

I'll update for the next version.


>>
>>> +
>>> +	fd_ = fd;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>  /*
>>>   * \brief List and store information about all controls supported by the
>>>   * V4L2 device
>>
> 

-- 
Regards
--
Kieran