1 files changed, 72 insertions, 0 deletions
diff --git a/sysfs.c b/sysfs.c
new file mode 100644
index 0000000..e073aa8
--- /dev/null
+++ b/sysfs.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Helpers for querying USB properties from sysfs
+ *
+ * Copied from name.c which is:
+ * Copyright (C) 1999, 2000 Thomas Sailer (sailer@ife.ee.ethz.ch)
+ * Copyright (C) 2013 Tom Gundersen (teg@jklm.no)
+ */
+
+#include <stdint.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <linux/limits.h>
+
+#include <libusb.h>
+
+#include "sysfs.h"
+
+/*
+ * The documentation of libusb_get_port_numbers() says "As per the USB 3.0
+ * specs, the current maximum limit for the depth is 7."
+ */
+#define USB_MAX_DEPTH 7
+
+#define SYSFS_DEV_ATTR_PATH "/sys/bus/usb/devices/%s/%s"
+
+int get_sysfs_name(char *buf, size_t size, libusb_device *dev)
+{
+	int len = 0;
+	uint8_t bnum = libusb_get_bus_number(dev);
+	uint8_t pnums[USB_MAX_DEPTH];
+	int num_pnums;
+
+	buf[0] = '\0';
+
+	num_pnums = libusb_get_port_numbers(dev, pnums, sizeof(pnums));
+	if (num_pnums == LIBUSB_ERROR_OVERFLOW) {
+		return -1;
+	} else if (num_pnums == 0) {
+		/* Special-case root devices */
+		return snprintf(buf, size, "usb%d", bnum);
+	}
+
+	len += snprintf(buf, size, "%d-", bnum);
+	for (int i = 0; i < num_pnums; i++)
+		len += snprintf(buf + len, size - len, i ? ".%d" : "%d", pnums[i]);
+
+	return len;
+}
+
+int read_sysfs_prop(char *buf, size_t size, char *sysfs_name, char *propname)
+{
+	int n, fd;
+	char path[PATH_MAX];
+
+	buf[0] = '\0';
+	snprintf(path, sizeof(path), SYSFS_DEV_ATTR_PATH, sysfs_name, propname);
+	fd = open(path, O_RDONLY);
+
+	if (fd == -1)
+		return 0;
+
+	n = read(fd, buf, size);
+
+	if (n > 0)
+		buf[n-1] = '\0';  // Turn newline into null terminator
+
+	close(fd);
+	return n;
+}