[libcamera-devel] [PATCH v7 3/9] libcamera: v4l2_device: Add method to lookup device path

[Niklas Söderlund]

Hi Jacopo,

Thanks for your feedback.

On 2020-08-05 09:25:40 +0200, Jacopo Mondi wrote:
> Hi Niklas,
> 
> On Tue, Aug 04, 2020 at 06:13:52PM +0200, Niklas Söderlund wrote:
> > Add a method to lookup a V4L2 devices path in sysfs.
> >
> > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > ---
> > * Changes since v6
> > - Use sysfs:: helper.
> > - Do not try to return std::string { nullptr } on error.
> >
> > * Changes since v5
> > - Expand documentation
> > - Use DeviceEnumerator interface to lookup device path
> > - Include stdlib.h
> > - Use realpath(..., nullptr); ...; free();
> >
> > * Changes since v3
> > - s/the device path/the device path in sysfs/
> > ---
> >  include/libcamera/internal/v4l2_device.h |  1 +
> >  src/libcamera/v4l2_device.cpp            | 28 ++++++++++++++++++++++++
> >  2 files changed, 29 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;
> >
> >  protected:
> >  	V4L2Device(const std::string &deviceNode);
> > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > index 56ea1ddda2c1425f..e55deabed46e30d4 100644
> > --- a/src/libcamera/v4l2_device.cpp
> > +++ b/src/libcamera/v4l2_device.cpp
> > @@ -9,12 +9,15 @@
> >
> >  #include <fcntl.h>
> >  #include <iomanip>
> > +#include <limits.h>
> 
> Is limits.h a leftover from when you used MAX_PATH ?

No, it's required for realpath();

> 
> > +#include <stdlib.h>
> >  #include <string.h>
> >  #include <sys/ioctl.h>
> >  #include <sys/syscall.h>
> >  #include <unistd.h>
> >
> >  #include "libcamera/internal/log.h"
> > +#include "libcamera/internal/sysfs.h"
> >  #include "libcamera/internal/utils.h"
> >  #include "libcamera/internal/v4l2_controls.h"
> >
> > @@ -350,6 +353,31 @@ int V4L2Device::setControls(ControlList *ctrls)
> >  	return ret;
> >  }
> >
> > +/**
> > + * \brief Retrieve the device path in sysfs
> > + *
> > + * This function returns the sysfs path to the physical device backing the V4L2
> > + * device. The path is guaranteed to be an absolute path, without any symbolic
> > + * link.
> > + *
> > + * \return The device path in sysfs
> > + */
> > +std::string V4L2Device::devicePath() const
> > +{
> > +	std::string devicePath = sysfs::charDevPath(deviceNode_) + "/device";
> > +
> > +	char *realPath = realpath(devicePath.c_str(), nullptr);
> > +	if (!realPath) {
> > +		LOG(V4L2, Fatal) << "Can not resolve path for " << devicePath;
> > +		return {};
> > +	}
> > +
> > +	std::string path{ realPath };
> > +	free(realPath);
> > +
> > +	return path;
> > +}
> > +
> 
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> 
> Thanks
>   j
> 
> >  /**
> >   * \brief Perform an IOCTL system call on the device node
> >   * \param[in] request The IOCTL request code
> > --
> > 2.28.0
> >
> > _______________________________________________
> > libcamera-devel mailing list
> > libcamera-devel at lists.libcamera.org
> > https://lists.libcamera.org/listinfo/libcamera-devel

-- 
Regards,
Niklas Söderlund