[libcamera-devel] [PATCH v3 4/5] libcamera: pipeline: uvcvideo: Generate unique camera names

[Jacopo Mondi]

Hi Niklas,

On Wed, Jul 29, 2020 at 01:42:24AM +0200, Niklas Söderlund wrote:
> Generate camera names that are unique and persistent between system
> resets. The name is constructed from the USB vendor and product
> information that is stored on USB device itself and the USB bus and
> device numbers where the hardware is plugged in.
>
> Before this change example of camera names:
>
> Venus USB2.0 Camera: Venus USB2
> Logitech Webcam C930e
>
> After this change the same cameras are:
>
> 0ac8:3420:3:10
> 046d:0843:3:4
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 34 +++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index 93e3dc17e3a7105e..72f3f5d9f7c414d0 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -6,6 +6,7 @@
>   */
>
>  #include <algorithm>
> +#include <fstream>
>  #include <iomanip>
>  #include <math.h>
>  #include <tuple>
> @@ -81,6 +82,9 @@ public:
>  	bool match(DeviceEnumerator *enumerator) override;
>
>  private:
> +	std::string generateName(const MediaDevice *media,
> +				 const std::string path);
> +
>  	int processControl(ControlList *controls, unsigned int id,
>  			   const ControlValue &value);
>  	int processControls(UVCCameraData *data, Request *request);
> @@ -379,6 +383,28 @@ int PipelineHandlerUVC::queueRequestDevice(Camera *camera, Request *request)
>  	return 0;
>  }
>
> +std::string PipelineHandlerUVC::generateName(const MediaDevice *media,

Is media used ?

> +					     const std::string path)

I would have passed the CameraData instance and got the path from
there.

> +{
> +	static const std::vector<std::string> files = { "idVendor", "idProduct", "busnum", "devnum" };

less than 120 cols ?

> +	std::vector<std::string> values;
> +	std::string value;
> +
> +	for (const std::string &name : files) {
> +		std::ifstream file(path + "/../" + name);
> +
> +		if (!file.is_open())
> +			return "";

Return or just skip that file ? If you want to return is this worth an
error message ?
> +
> +		std::getline(file, value);
> +		file.close();

This applies to the other patches as well, reading
std::ifstream::close documentation I see:

"Note that any open file is automatically closed when the ifstream object is destroyed."

Do you need to call close ? I got suspicious as it felt weird that an
STL library opens a file on construction but requires manual closure..

> +
> +		values.push_back(value);
> +	}
> +
> +	return utils::join(values, ":");
> +}
> +
>  bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
>  {
>  	MediaDevice *media;
> @@ -405,8 +431,14 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
>  		return false;
>
>  	/* Create and register the camera. */
> +	std::string name = generateName(media, data->video_->devicePath());
> +	if (name.empty()) {
> +		LOG(UVC, Error) << "Failed to generate camera name";
> +		return false;
> +	}

Oh the error is here, and is better here than in the function. But
then you have to fail if you don't find one of the files... I think
what you have here is right then...

> +
>  	std::set<Stream *> streams{ &data->stream_ };
> -	std::shared_ptr<Camera> camera = Camera::create(this, media->model(), streams);
> +	std::shared_ptr<Camera> camera = Camera::create(this, name, streams);

nits apart
Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Thanks
  j

>  	registerCamera(std::move(camera), std::move(data));
>
>  	/* Enable hot-unplug notifications. */
> --
> 2.27.0
>
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