[libcamera-devel] [PATCH v7 7/9] libcamera: pipeline: uvcvideo: Generate unique camera names

[Niklas Söderlund]

Hi Laurent,

Thanks for your feedback.

On 2020-08-04 21:52:47 +0300, Laurent Pinchart wrote:
> Hi Niklas,
> 
> Thank you for the patch.
> 
> On Tue, Aug 04, 2020 at 06:13:56PM +0200, Niklas Söderlund wrote:
> > Generate camera names that are unique and persistent between system
> > resets. The name is constructed from the USB device information as well
> > as the USB controller on the host.
> > 
> > Before this change example of camera names:
> > 
> > Venus USB2.0 Camera: Venus USB2
> > Logitech Webcam C930e
> > 
> > After this change the same cameras are:
> > 
> > \_SB_.PCI0.RP05.PXSX-2.1.1:1.0-0ac8:3420
> > \_SB_.PCI0.RP05.PXSX-2.4:1.0-046d:0843
> > 
> > On OF-based system:
> > 
> > base/soc/usb at 7e980000/usb-port at 1-1.3:1.0-0ac8:3420
> > 
> > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > ---
> > * Changes since v5
> > - New algorithm to generate IDs.
> > 
> > * Changes since v3
> > - Switch argument to generateName() to UVCCameraData pointer.
> > ---
> >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 77 +++++++++++++++++++-
> >  1 file changed, 76 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > index 93e3dc17e3a7105e..70c057b543f85c7b 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>
> > @@ -20,6 +21,7 @@
> >  #include "libcamera/internal/log.h"
> >  #include "libcamera/internal/media_device.h"
> >  #include "libcamera/internal/pipeline_handler.h"
> > +#include "libcamera/internal/sysfs.h"
> >  #include "libcamera/internal/utils.h"
> >  #include "libcamera/internal/v4l2_controls.h"
> >  #include "libcamera/internal/v4l2_videodevice.h"
> > @@ -81,6 +83,8 @@ public:
> >  	bool match(DeviceEnumerator *enumerator) override;
> >  
> >  private:
> > +	std::string generateID(const UVCCameraData *data);
> 
> s/ID/Id/
> 
> > +
> >  	int processControl(ControlList *controls, unsigned int id,
> >  			   const ControlValue &value);
> >  	int processControls(UVCCameraData *data, Request *request);
> > @@ -379,6 +383,71 @@ int PipelineHandlerUVC::queueRequestDevice(Camera *camera, Request *request)
> >  	return 0;
> >  }
> >  
> > +std::string PipelineHandlerUVC::generateID(const UVCCameraData *data)
> > +{
> > +	const std::string path = data->video_->devicePath();
> > +
> > +	/* Creata a device ID from the USB devices vendor and product ID. */
> > +	std::string deviceId;
> > +	for (const std::string &name : { "idVendor", "idProduct" }) {
> > +		std::ifstream file(path + "/../" + name);
> > +
> > +		if (!file.is_open())
> > +			return {};
> > +
> > +		std::string value;
> > +		std::getline(file, value);
> > +		file.close();
> > +
> > +		deviceId += value + (deviceId.empty() ? ":" : "");
> 
> 		if (!deviceId.empty())
> 			deviceId += ":";
> 
> 		deviceId += value;
> 
> so this will work with more than two iterations :-)

:-)

> 
> > +	}
> 
> Of course you could also use utils::join() if you wanted.
> 
> I'd move this block after the next, to follow the same order as in the
> ID string, but maybe it's just me.

I had not noticed but now that it's pointed out it drives me mad, I will 
sort them to match the output order :-)

> 
> > +
> > +	/*
> > +	 * Create a USB ID from the device path which has the known format:
> > +	 *
> > +	 *	bus , "-", ports, ":", config, ".", interface ;
> 
> s/bus ,/ bus,/ (maybe path = ... ?)

Good catch, I also like adding of path = ... .

> 
> > +	 *	bus = number ;
> > +	 *	ports = port, [ ".", ports ] ;
> > +	 *	port = number ;
> > +	 *	config = number ;
> > +	 *	interface = number ;
> > +	 *
> > +	 * Example: 3-2.4:1.0
> > +	 *
> > +	 * The bus is not guaranteed to be stable and needs to be stripped from
> > +	 * the USB ID. The final USB ID is built up of the ports, config and
> > +	 * interface properties.
> > +	 *
> > +	 * Example 2.4:1.0.
> > +	 */
> > +	std::string usbId = basename(path.c_str());
> > +	usbId = usbId.substr(usbId.find('-') + 1, std::string::npos);
> 
> The second argument defaults to std::string::npos, so you could leave it
> out if you wanted.
> 
> > +
> > +	/* Create a controller ID from first device described in firmware. */
> > +	std::string controllerId;
> > +	std::string searchPath = path;
> > +	while (true) {
> > +		searchPath += "/..";
> > +		char *realPath = realpath(searchPath.c_str(), nullptr);
> > +		if (!realPath) {
> > +			LOG(UVC, Error) << "Failed to lookup " << searchPath;
> > +			return {};
> > +		}
> > +		searchPath = realPath;
> > +		free(realPath);
> > +
> > +		if (searchPath.empty() || searchPath == "/") {
> > +			LOG(UVC, Error) << "Can not find controller ID";
> > +			return {};
> > +		}
> 
> As path is guaranteed to be a real path, I think this could be
> simplified.
> 
> 		std::string::size_type pos = searchPath.rfind('-');

With s@'-'@'/'@ it works and is much nicer, thanks for this snippet.

> 		if (pos <= 1) {
> 			LOG(UVC, Error) << "Can not find controller ID";
> 			return {};
> 		}
> 
> 		searchPath = searchPath::substr(0, pos);
> 
> > +
> > +		if (!sysfs::firmwareId(searchPath, &controllerId))
> > +			break;
> > +	}
> > +
> > +	return controllerId + "-" + usbId + "-" + deviceId;
> > +}
> > +
> >  bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
> >  {
> >  	MediaDevice *media;
> > @@ -405,8 +474,14 @@ bool PipelineHandlerUVC::match(DeviceEnumerator *enumerator)
> >  		return false;
> >  
> >  	/* Create and register the camera. */
> > +	std::string id = generateID(data.get());
> > +	if (id.empty()) {
> > +		LOG(UVC, Error) << "Failed to generate camera ID";
> > +		return false;
> > +	}
> > +
> >  	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, id, streams);
> >  	registerCamera(std::move(camera), std::move(data));
> >  
> >  	/* Enable hot-unplug notifications. */
> 
> -- 
> Regards,
> 
> Laurent Pinchart

-- 
Regards,
Niklas Söderlund