[libcamera-devel] [PATCH v2] libcamera: v4l2device: Obtain device capabilities

[Laurent Pinchart]

Hi Niklas,

Thank you for the patch.

On Wed, Jan 23, 2019 at 01:45:30PM +0000, Kieran Bingham wrote:
> The capabilities structure from the kernel can return capabilities of the
> driver, or potentially more specific device capabilities.
> 
> Handle this with an inline function 'device_caps()' to return the device
> specific capabilities when available, or fall back to the driver capabilities
> otherwise.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  src/libcamera/include/v4l2_device.h | 12 +++++++++---
>  src/libcamera/v4l2_device.cpp       |  7 +++++++
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
> index b92e1f1c96c3..cb3601ca070c 100644
> --- a/src/libcamera/include/v4l2_device.h
> +++ b/src/libcamera/include/v4l2_device.h
> @@ -26,10 +26,16 @@ struct V4L2Capability final : v4l2_capability {
>  	{
>  		return reinterpret_cast<const char *>(v4l2_capability::bus_info);
>  	}
> +	unsigned int device_caps() const
> +	{
> +		return capabilities & V4L2_CAP_DEVICE_CAPS
> +				    ? v4l2_capability::device_caps
> +				    : v4l2_capability::capabilities;
> +	}
>  
> -	bool isCapture() const { return capabilities & V4L2_CAP_VIDEO_CAPTURE; }
> -	bool isOutput() const { return capabilities & V4L2_CAP_VIDEO_OUTPUT; }
> -	bool hasStreaming() const { return capabilities & V4L2_CAP_STREAMING; }
> +	bool isCapture() const { return device_caps() & V4L2_CAP_VIDEO_CAPTURE; }
> +	bool isOutput() const { return device_caps() & V4L2_CAP_VIDEO_OUTPUT; }
> +	bool hasStreaming() const { return device_caps() & V4L2_CAP_STREAMING; }

We're probably reaching the limit of what inline functions should do. If
another layer of indirection is needed we may want to de-inline some of
the functions. It's fine for now.

>  };
>  
>  class MediaEntity;
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index 2b17fa1eb0e8..0ce2b187f2f0 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -49,6 +49,13 @@ LOG_DEFINE_CATEGORY(V4L2)
>   * \return The string containing the device location
>   */
>  
> +/**
> + * \fn unsigned int V4L2Capability::device_caps()
> + * \brief Retrieve the capabilities of the device
> + * \return The device specific capabilities if V4L2_CAP_DEVICE_CAPS is set or
> + * 	   driver capabilities otherwise

No need for special indentation here. This doesn't require a fix in a
follow-up patch, but you could fix it if you touch this code later.

> + */
> +
>  /**
>   * \fn bool V4L2Capability::isCapture()
>   * \brief Identify if the device is capable of capturing video

-- 
Regards,

Laurent Pinchart