[libusb] [PATCH 3/7] linux_usbfs: Get device address from file descriptor

[Vianney le C. de Saint-M. <co...@qu...>]

Extend linux_get_device_address() to try to read the device address from
a file descriptor as a last resort, if provided.

Additionally, linux_get_device_address() will now return an error if the
path could not be parsed.

Signed-off-by: Vianney le Clément de Saint-Marcq <co...@qu...>
---
 libusb/os/linux_udev.c  |  2 +-
 libusb/os/linux_usbfs.c | 15 +++++++++++++--
 libusb/os/linux_usbfs.h |  2 +-
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/libusb/os/linux_udev.c b/libusb/os/linux_udev.c
index c97806ba..bea03e3a 100644
--- a/libusb/os/linux_udev.c
+++ b/libusb/os/linux_udev.c
@@ -232,7 +232,7 @@ static int udev_device_info(struct libusb_context *ctx, int detached,
 	}
 
 	return linux_get_device_address(ctx, detached, busnum, devaddr,
-					dev_node, *sys_name);
+					dev_node, *sys_name, -1);
 }
 
 static void udev_hotplug_event(struct udev_device* udev_dev)
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index dfbb6c4b..addde884 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -687,14 +687,23 @@ static int sysfs_get_active_config(struct libusb_device *dev, int *config)
 
 int linux_get_device_address (struct libusb_context *ctx, int detached,
 	uint8_t *busnum, uint8_t *devaddr,const char *dev_node,
-	const char *sys_name)
+	const char *sys_name, int fd)
 {
+	char proc_path[PATH_MAX], fd_path[PATH_MAX];
 	int sysfs_attr;
+	ssize_t r;
 
 	usbi_dbg("getting address for device: %s detached: %d", sys_name, detached);
 	/* can't use sysfs to read the bus and device number if the
 	 * device has been detached */
 	if (!sysfs_can_relate_devices || detached || NULL == sys_name) {
+		if (NULL == dev_node && fd >= 0) {
+			/* try to retrieve the device node from fd */
+			snprintf(proc_path, PATH_MAX, "/proc/self/fd/%d", fd);
+			r = readlink(proc_path, fd_path, PATH_MAX);
+			if (r > 0)
+				dev_node = fd_path;
+		}
 		if (NULL == dev_node) {
 			return LIBUSB_ERROR_OTHER;
 		}
@@ -704,6 +713,8 @@ int linux_get_device_address (struct libusb_context *ctx, int detached,
 			sscanf (dev_node, "/dev/bus/usb/%hhu/%hhu", busnum, devaddr);
 		} else if (!strncmp(dev_node, "/proc/bus/usb", 13)) {
 			sscanf (dev_node, "/proc/bus/usb/%hhu/%hhu", busnum, devaddr);
+		} else {
+			return LIBUSB_ERROR_OTHER;
 		}
 
 		return LIBUSB_SUCCESS;
@@ -1287,7 +1298,7 @@ static int sysfs_scan_device(struct libusb_context *ctx, const char *devname)
 	uint8_t busnum, devaddr;
 	int ret;
 
-	ret = linux_get_device_address (ctx, 0, &busnum, &devaddr, NULL, devname);
+	ret = linux_get_device_address (ctx, 0, &busnum, &devaddr, NULL, devname, -1);
 	if (LIBUSB_SUCCESS != ret) {
 		return ret;
 	}
diff --git a/libusb/os/linux_usbfs.h b/libusb/os/linux_usbfs.h
index 24496325..a57eb413 100644
--- a/libusb/os/linux_usbfs.h
+++ b/libusb/os/linux_usbfs.h
@@ -187,7 +187,7 @@ void linux_device_disconnected(uint8_t busnum, uint8_t devaddr);
 
 int linux_get_device_address (struct libusb_context *ctx, int detached,
 	uint8_t *busnum, uint8_t *devaddr, const char *dev_node,
-	const char *sys_name);
+	const char *sys_name, int fd);
 int linux_enumerate_device(struct libusb_context *ctx,
 	uint8_t busnum, uint8_t devaddr, const char *sysfs_dir);
 
-- 
2.19.2