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-rw-r--r--src/libcamera/sysfs.cpp58
1 files changed, 58 insertions, 0 deletions
diff --git a/src/libcamera/sysfs.cpp b/src/libcamera/sysfs.cpp
index 398df2c2..6c8e9554 100644
--- a/src/libcamera/sysfs.cpp
+++ b/src/libcamera/sysfs.cpp
@@ -7,10 +7,12 @@
#include "libcamera/internal/sysfs.h"
+#include <fstream>
#include <sstream>
#include <sys/stat.h>
#include <sys/sysmacros.h>
+#include "libcamera/internal/file.h"
#include "libcamera/internal/log.h"
/**
@@ -47,6 +49,62 @@ std::string charDevPath(const std::string &deviceNode)
return dev.str();
}
+/**
+ * \brief Retrieve the path of the firmware node for a device
+ * \param[in] device Path in sysfs to search
+ *
+ * Physical devices in a system are described by the system firmware. Depending
+ * on the type of platform, devices are identified using different naming
+ * schemes. The Linux kernel abstract those differences with "firmware nodes".
+ * This function retrieves the firmware node path corresponding to the
+ * \a device.
+ *
+ * For DT-based systems, the path is the full name of the DT node that
+ * represents the device. For ACPI-based systems, the path is the absolute
+ * namespace path to the ACPI object that represents the device. In both cases,
+ * the path is guaranteed to be unique and persistent as long as the system
+ * firmware is not modified.
+ *
+ * \return The firmware node path on success or an empty string on failure
+ */
+std::string firmwareNodePath(const std::string &device)
+{
+ std::string fwPath, node;
+
+ /* Lookup for DT-based systems */
+ node = device + "/of_node";
+ if (File::exists(node)) {
+ char *ofPath = realpath(node.c_str(), nullptr);
+ if (!ofPath)
+ return {};
+
+ static const char prefix[] = "/sys/firmware/devicetree";
+ if (strncmp(ofPath, prefix, strlen(prefix)) == 0)
+ fwPath = ofPath + strlen(prefix);
+ else
+ fwPath = ofPath;
+
+ free(ofPath);
+
+ return fwPath;
+ }
+
+ /* Lookup for ACPI-based systems */
+ node = device + "/firmware_node/path";
+ if (File::exists(node)) {
+ std::ifstream file(node);
+ if (!file.is_open())
+ return {};
+
+ std::getline(file, fwPath);
+ file.close();
+
+ return fwPath;
+ }
+
+ return {};
+}
+
} /* namespace sysfs */
} /* namespace libcamera */