[libcamera-devel] [PATCH v7 1/9] libcamera: sysfs: Add new namespace to interact with sysfs

[Jacopo Mondi]

Hi Niklas,

On Tue, Aug 04, 2020 at 07:26:01PM +0300, Laurent Pinchart wrote:
> Hi Niklas,
>
> Thank you for the patch.
>
> On Tue, Aug 04, 2020 at 06:13:50PM +0200, Niklas Söderlund wrote:
> > To support stable and unique camera IDs access to information in sysfs
> > is needed. Add a new libcamera::sysfs namespace to contain such sysfs
> > helpers.
> >
> > As a first helper add a method to lookup a character device sysfs path.
>
> I would have turned this the other way around ("Add a helper function to
> lookup the sysfs path of a character device. Store the function in a new
> libcamera::sysfs namespace as there is not class to host it.") but it
> doesn't matter much.
>
> > Suggested-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> > ---
> >  include/libcamera/internal/meson.build |  1 +
> >  include/libcamera/internal/sysfs.h     | 22 ++++++++++++
> >  src/libcamera/meson.build              |  1 +
> >  src/libcamera/sysfs.cpp                | 48 ++++++++++++++++++++++++++
> >  4 files changed, 72 insertions(+)
> >  create mode 100644 include/libcamera/internal/sysfs.h
> >  create mode 100644 src/libcamera/sysfs.cpp
> >
> > diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
> > index d868eff47f920da0..150103388fdb219d 100644
> > --- a/include/libcamera/internal/meson.build
> > +++ b/include/libcamera/internal/meson.build
> > @@ -25,6 +25,7 @@ libcamera_internal_headers = files([
> >      'process.h',
> >      'pub_key.h',
> >      'semaphore.h',
> > +    'sysfs.h',
> >      'thread.h',
> >      'utils.h',
> >      'v4l2_controls.h',
> > diff --git a/include/libcamera/internal/sysfs.h b/include/libcamera/internal/sysfs.h
> > new file mode 100644
> > index 0000000000000000..72f436205d8d30e8
> > --- /dev/null
> > +++ b/include/libcamera/internal/sysfs.h
> > @@ -0,0 +1,22 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2020, Google Inc.
> > + *
> > + * sysfs.h - Miscellaneous utility functions to access sysfs
> > + */
> > +#ifndef __LIBCAMERA_INTERNAL_SYSFS_H__
> > +#define __LIBCAMERA_INTERNAL_SYSFS_H__
> > +
> > +#include <string>
> > +
> > +namespace libcamera {
> > +
> > +namespace sysfs {
> > +
> > +std::string charDevPath(const std::string &devicePath);
>
> s/devicePath/deviceNode/
>
> > +
> > +} /* namespace sysfs */
> > +
> > +} /* namespace libcamera */
> > +
> > +#endif /* __LIBCAMERA_INTERNAL_SYSFS_H__ */
> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> > index 3aad4386ffc296db..bada45bcb11e9e88 100644
> > --- a/src/libcamera/meson.build
> > +++ b/src/libcamera/meson.build
> > @@ -41,6 +41,7 @@ libcamera_sources = files([
> >      'semaphore.cpp',
> >      'signal.cpp',
> >      'stream.cpp',
> > +    'sysfs.cpp',
> >      'thread.cpp',
> >      'timer.cpp',
> >      'utils.cpp',
> > diff --git a/src/libcamera/sysfs.cpp b/src/libcamera/sysfs.cpp
> > new file mode 100644
> > index 0000000000000000..3b2920663e9c3bcc
> > --- /dev/null
> > +++ b/src/libcamera/sysfs.cpp
> > @@ -0,0 +1,48 @@
> > +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> > +/*
> > + * Copyright (C) 2020, Google Inc.
> > + *
> > + * sysfs.cpp - Miscellaneous utility functions to access sysfs
> > + */
> > +
> > +#include "libcamera/internal/sysfs.h"
> > +
>
> #include <sstream>
>
> for std::ostringstream.
>
> > +#include <sys/stat.h>
> > +#include <sys/sysmacros.h>
> > +
> > +#include "libcamera/internal/log.h"
> > +
> > +/**
> > + * \file sysfs.h
> > + * \brief Miscellaneous utility functions to access sysfs
> > + */
> > +
> > +namespace libcamera {
> > +
> > +LOG_DEFINE_CATEGORY(SYSFS);
>
> SysFs ? Up to you.
>
> > +
> > +namespace sysfs {
> > +
> > +/**
> > + * \brief Retrive the sysfs path for a characther device
>
> s/Retrive/Retrieve/
> s/characther/character/
>
> > + * \param[in] devicePath Path to charachter device
>
> s/devicePath/deviceNode/
> s/charachter/character/
> s/device$/device node/
>
> > + * \return The sysfs path on success or empty string on failure
>
> s/empty/an empty/
>
> > + */
> > +std::string charDevPath(const std::string &devicePath)
>
> s/devicePath/deviceNode/
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
> > +{
> > +	struct stat st;
> > +	int ret = stat(devicePath.c_str(), &st);
> > +	if (ret < 0) {
> > +		LOG(SYSFS, Error)
> > +			<< "Unable to stat '" << devicePath << "'";

As you have to rework it, I think the stat error is relevant to be
printed out

> > +		return {};
> > +	}
> > +
> > +	std::ostringstream dev("/sys/dev/char/", std::ios_base::ate);
> > +	dev << major(st.st_rdev) << ":" << minor(st.st_rdev);

Usually we have an empty line before return.

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

Thanks
  j

> > +	return dev.str();
> > +}
> > +
> > +} /* namespace sysfs */
> > +
> > +} /* namespace libcamera */
>
> --
> Regards,
>
> Laurent Pinchart
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