linux: Switch to kernel version check to determine if sysfs can relate devs

We rely on the kernel version for determining capabilities, except for
sysfs_can_relate_devices. This changes sysfs_can_relate_devices over to
a kernel version check to.

This makes things more consistent, removes a whole bunch of code, and since
it stops us from needlessly banging sysfs, it reduces the avarage run time for
the stress test on my system from 21.8 to 16.7 seconds.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 5b7cf40..5e79ea0 100644 (file)
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -51,13 +51,13 @@
  *  - The binary "descriptors" file was added in 2.6.23, commit
  *    69d42a78f935d19384d1f6e4f94b65bb162b36df, but it only contains the
  *    active config descriptors
- *  - The "busnum" file was added in 2.6.22
+ *  - The "busnum" file was added in 2.6.22, commit
+ *    83f7d958eab2fbc6b159ee92bf1493924e1d0f72
  *  - The "devnum" file has been present since pre-2.6.18
  *  - the "bConfigurationValue" file has been present since pre-2.6.18
  *
  * If we have bConfigurationValue, busnum, and devnum, then we can determine
  * the active configuration without having to open the usbfs node in RDWR mode.
- * We assume this is the case if we see the busnum file (indicates 2.6.22+).
  * The busnum file is important as that is the only way we can relate sysfs
  * devices to usbfs nodes.
  *
@@ -106,9 +106,10 @@ static int supports_flag_zero_packet = -1;
  * systems. appropriate choice made at initialization time. */
 static clockid_t monotonic_clkid = -1;
 
-/* do we have a busnum to relate devices? this also implies that we can read
+/* Linux 2.6.22 (commit 83f7d958eab2fbc6b159ee92bf1493924e1d0f72) adds a busnum
+ * to sysfs, so we can relate devices. This also implies that we can read
  * the active configuration through bConfigurationValue */
-static int sysfs_can_relate_devices = 0;
+static int sysfs_can_relate_devices = -1;
 
 /* Linux 2.6.26 (commit 217a9081d8e69026186067711131b77f0ce219ed) adds all
  * config descriptors (rather then just the active config) to the sysfs
@@ -345,22 +346,6 @@ static int kernel_version_ge(int major, int minor, int sublevel)
        return ksublevel >= sublevel;
 }
 
-/* Return 1 if filename exists inside dirname in sysfs.
-   SYSFS_DEVICE_PATH is assumed to be the beginning of the path. */
-static int sysfs_has_file(const char *dirname, const char *filename)
-{
-       struct stat statbuf;
-       char path[PATH_MAX];
-       int r;
-
-       snprintf(path, PATH_MAX, "%s/%s/%s", SYSFS_DEVICE_PATH, dirname, filename);
-       r = stat(path, &statbuf);
-       if (r == 0 && S_ISREG(statbuf.st_mode))
-               return 1;
-
-       return 0;
-}
-
 static int op_init(struct libusb_context *ctx)
 {
        struct stat statbuf;
@@ -408,57 +393,30 @@ static int op_init(struct libusb_context *ctx)
                }
        }
 
-       r = stat(SYSFS_DEVICE_PATH, &statbuf);
-       if (r == 0 && S_ISDIR(statbuf.st_mode)) {
-               DIR *devices = opendir(SYSFS_DEVICE_PATH);
-               struct dirent *entry;
-
-               usbi_dbg("found usb devices in sysfs");
-
-               if (!devices) {
-                       usbi_err(ctx, "opendir devices failed errno=%d", errno);
-                       return LIBUSB_ERROR_IO;
+       if (-1 == sysfs_can_relate_devices) {
+               /* sysfs has busnum since Linux 2.6.22 */
+               sysfs_can_relate_devices = kernel_version_ge(2,6,22);
+               if (-1 == sysfs_can_relate_devices) {
+                       usbi_err(ctx, "error checking for sysfs busnum");
+                       return LIBUSB_ERROR_OTHER;
                }
+       }
 
-               /* Make sure sysfs supports all the required files. If it
-                * does not, then usbfs will be used instead.  Determine
-                * this by looping through the directories in
-                * SYSFS_DEVICE_PATH.  With the assumption that there will
-                * always be subdirectories of the name usbN (usb1, usb2,
-                * etc) representing the root hubs, check the usbN
-                * subdirectories to see if they have all the needed files.
-                * This algorithm uses the usbN subdirectories (root hubs)
-                * because a device disconnection will cause a race
-                * condition regarding which files are available, sometimes
-                * causing an incorrect result.  The root hubs are used
-                * because it is assumed that they will always be present.
-                * See the "sysfs vs usbfs" comment at the top of this file
-                * for more details.  */
-               while ((entry = readdir(devices))) {
-                       int has_busnum=0, has_devnum=0;
-                       int has_configuration_value=0;
-
-                       /* Only check the usbN directories. */
-                       if (strncmp(entry->d_name, "usb", 3) != 0)
-                               continue;
-
-                       /* Check for the files libusbx needs from sysfs. */
-                       has_busnum = sysfs_has_file(entry->d_name, "busnum");
-                       has_devnum = sysfs_has_file(entry->d_name, "devnum");
-                       has_configuration_value = sysfs_has_file(entry->d_name, "bConfigurationValue");
-
-                       if (has_busnum && has_devnum && has_configuration_value) {
-                               sysfs_can_relate_devices = 1;
-                               break;
-                       }
+       if (sysfs_can_relate_devices || sysfs_has_descriptors) {
+               r = stat(SYSFS_DEVICE_PATH, &statbuf);
+               if (r != 0 || !S_ISDIR(statbuf.st_mode)) {
+                       usbi_warn(ctx, "sysfs not mounted");
+                       sysfs_can_relate_devices = 0;
+                       sysfs_has_descriptors = 0;
                }
-               closedir(devices);
-       } else {
-               usbi_dbg("sysfs usb info not available");
-               sysfs_has_descriptors = 0;
-               sysfs_can_relate_devices = 0;
        }
 
+       if (sysfs_can_relate_devices)
+               usbi_dbg("sysfs can relate devices");
+
+       if (sysfs_has_descriptors)
+               usbi_dbg("sysfs has complete descriptors");
+
        usbi_mutex_static_lock(&hotplug_lock);
        r = LIBUSB_SUCCESS;
        if (init_count == 0) {

diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 27ae94c..0a6f397 100644 (file)
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 10704
+#define LIBUSB_NANO 10705