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

[Laurent Pinchart]

Hi Kieran,

On Mon, Aug 12, 2019 at 10:13:01AM +0100, Kieran Bingham wrote:
> On 12/08/2019 08:20, Kieran Bingham wrote:
> > On 09/08/2019 23:48, Laurent Pinchart wrote:
> >> 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.

Sounds good to me, you can keep my Rb.

> 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,

Laurent Pinchart