[libcamera-devel] [PATCH v4 1/5] libcamera: v4l2_device: Add method to lookup device path

[Niklas Söderlund]

Hi Kieran,

Thanks for your feedback.

On 2020-07-29 11:28:12 +0100, Kieran Bingham wrote:
> Hi Niklas,
> 
> This looks fine to me.
> 
> On 29/07/2020 10:21, Niklas Söderlund wrote:
> > Add a method to lookup a V4L2 devices path in sysfs.
> > 
> > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> > ---
> > * Changes since v3
> > - s/the device path/the device path in sysfs/
> > ---
> >  include/libcamera/internal/v4l2_device.h |  1 +
> >  src/libcamera/v4l2_device.cpp            | 24 ++++++++++++++++++++++++
> >  2 files changed, 25 insertions(+)
> > 
> > diff --git a/include/libcamera/internal/v4l2_device.h b/include/libcamera/internal/v4l2_device.h
> > index bf643f2ec966bb33..3b605aab343b3b94 100644
> > --- a/include/libcamera/internal/v4l2_device.h
> > +++ b/include/libcamera/internal/v4l2_device.h
> > @@ -30,6 +30,7 @@ public:
> >  	int setControls(ControlList *ctrls);
> >  
> >  	const std::string &deviceNode() const { return deviceNode_; }
> > +	std::string devicePath() const;
> 
> I wonder if it warrants a simple addition in the test/v4l2_videodevice/
> but I'm not sure what it would actually do other than simply call it and
> make sure 'something' returns, which might not be much added value.

The error is fatal so if nothing is returned we would terminate 
execution ;-)

> 
> 
> But for this addition anyway:
> 
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> >  
> >  protected:
> >  	V4L2Device(const std::string &deviceNode);
> > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > index 56ea1ddda2c1425f..1cb8181ab6fd5a8d 100644
> > --- a/src/libcamera/v4l2_device.cpp
> > +++ b/src/libcamera/v4l2_device.cpp
> > @@ -9,6 +9,7 @@
> >  
> >  #include <fcntl.h>
> >  #include <iomanip>
> > +#include <limits.h>
> >  #include <string.h>
> >  #include <sys/ioctl.h>
> >  #include <sys/syscall.h>
> > @@ -350,6 +351,29 @@ int V4L2Device::setControls(ControlList *ctrls)
> >  	return ret;
> >  }
> >  
> > +/**
> > + * \brief Retrieve the device path in sysfs
> > + *
> > + * The device path in sysfs describes the device backing the V4L2 device.
> > + *
> > + * \todo When switching to C++17 use std::filesystem:: in the implementation.
> > + * \todo Query udev for this information as the path created for vdev here
> > + * migh not be correct.
> > + *
> > + * \return The device path in sysfs
> > + */
> > +std::string V4L2Device::devicePath() const
> > +{
> > +	std::string vdev = basename(deviceNode_.c_str());
> > +	std::string sysfs = "/sys/class/video4linux/" + vdev + "/device";
> > +
> > +	char path[PATH_MAX];
> > +	if (!realpath(sysfs.c_str(), path))
> > +		LOG(V4L2, Fatal) << "Can not resolve path for " << deviceNode_;
> > +
> > +	return path;
> > +}
> > +
> >  /**
> >   * \brief Perform an IOCTL system call on the device node
> >   * \param[in] request The IOCTL request code
> > 
> 
> -- 
> Regards
> --
> Kieran

-- 
Regards,
Niklas Söderlund