b304bc013e
The File abstraction is a base helper and not part of the libcamera API. Move it to to allow usage by users of the base library. Reviewed-by: Hirokazu Honda <hiroh@chromium.org> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
112 lines
2.7 KiB
C++
112 lines
2.7 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2020, Google Inc.
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*
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* sysfs.cpp - Miscellaneous utility functions to access sysfs
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*/
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#include "libcamera/internal/sysfs.h"
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#include <fstream>
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#include <sstream>
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#include <sys/stat.h>
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#include <sys/sysmacros.h>
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#include <libcamera/base/file.h>
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#include <libcamera/base/log.h>
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/**
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* \file sysfs.h
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* \brief Miscellaneous utility functions to access sysfs
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*/
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namespace libcamera {
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LOG_DEFINE_CATEGORY(SysFs)
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namespace sysfs {
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/**
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* \brief Retrieve the sysfs path for a character device
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* \param[in] deviceNode Path to character device node
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* \return The sysfs path on success or an empty string on failure
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*/
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std::string charDevPath(const std::string &deviceNode)
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{
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struct stat st;
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int ret = stat(deviceNode.c_str(), &st);
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if (ret < 0) {
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ret = -errno;
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LOG(SysFs, Error)
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<< "Unable to stat '" << deviceNode << "': "
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<< strerror(-ret);
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return {};
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}
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std::ostringstream dev("/sys/dev/char/", std::ios_base::ate);
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dev << major(st.st_rdev) << ":" << minor(st.st_rdev);
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return dev.str();
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}
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/**
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* \brief Retrieve the path of the firmware node for a device
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* \param[in] device Path in sysfs to search
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*
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* Physical devices in a system are described by the system firmware. Depending
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* on the type of platform, devices are identified using different naming
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* schemes. The Linux kernel abstract those differences with "firmware nodes".
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* This function retrieves the firmware node path corresponding to the
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* \a device.
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*
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* For DT-based systems, the path is the full name of the DT node that
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* represents the device. For ACPI-based systems, the path is the absolute
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* namespace path to the ACPI object that represents the device. In both cases,
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* the path is guaranteed to be unique and persistent as long as the system
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* firmware is not modified.
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*
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* \return The firmware node path on success or an empty string on failure
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*/
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std::string firmwareNodePath(const std::string &device)
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{
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std::string fwPath, node;
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struct stat st;
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/* Lookup for DT-based systems */
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node = device + "/of_node";
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if (!stat(node.c_str(), &st)) {
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char *ofPath = realpath(node.c_str(), nullptr);
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if (!ofPath)
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return {};
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static const char prefix[] = "/sys/firmware/devicetree";
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if (strncmp(ofPath, prefix, strlen(prefix)) == 0)
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fwPath = ofPath + strlen(prefix);
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else
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fwPath = ofPath;
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free(ofPath);
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return fwPath;
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}
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/* Lookup for ACPI-based systems */
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node = device + "/firmware_node/path";
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if (File::exists(node)) {
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std::ifstream file(node);
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if (!file.is_open())
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return {};
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std::getline(file, fwPath);
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file.close();
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return fwPath;
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}
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return {};
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}
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} /* namespace sysfs */
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} /* namespace libcamera */
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