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

[Laurent Pinchart]

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

-- 
Regards,

Laurent Pinchart