Linux: Rework bulk continuation check to generic kernel version check

The old check_flag_bulk_continuation() tested for one specific running
kernel version. The new kernel_version_ge() instead allows to test the
running kernel version against major, minor and sublevel parameters.

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 2b81189..2aa2026 100644 (file)
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -216,37 +216,35 @@ static clockid_t find_monotonic_clock(void)
        return CLOCK_REALTIME;
 }
 
-/* bulk continuation URB flag available from Linux 2.6.32 */
-static int check_flag_bulk_continuation(void)
+static int kernel_version_ge(int major, int minor, int sublevel)
 {
        struct utsname uts;
-       int atoms, major, minor, sublevel;
+       int atoms, kmajor, kminor, ksublevel;
 
        if (uname(&uts) < 0)
                return -1;
-       atoms = sscanf(uts.release, "%d.%d.%d", &major, &minor, &sublevel);
+       atoms = sscanf(uts.release, "%d.%d.%d", &kmajor, &kminor, &ksublevel);
        if (atoms < 1)
                return -1;
 
-       if (major > 2)
+       if (kmajor > major)
                return 1;
-       if (major < 2)
+       if (kmajor < major)
                return 0;
 
+       /* kmajor == major */
        if (atoms < 2)
-               return 0;
-
-       /* major == 2 */
-       if (minor < 6)
-               return 0;
-       if (minor > 6) /* Does not exist, just here for correctness */
+               return 0 == minor && 0 == sublevel;
+       if (kminor > minor)
                return 1;
+       if (kminor < minor)
+               return 0;
 
-       /* 2.6.x */
-       if (3 == atoms && sublevel >= 32)
-               return 1;
+       /* kminor == minor */
+       if (atoms < 3)
+               return 0 == sublevel;
 
-       return 0;
+       return ksublevel >= sublevel;
 }
 
 /* Return 1 if filename exists inside dirname in sysfs.
@@ -280,7 +278,8 @@ static int op_init(struct libusb_context *ctx)
                monotonic_clkid = find_monotonic_clock();
 
        if (supports_flag_bulk_continuation == -1) {
-               supports_flag_bulk_continuation = check_flag_bulk_continuation();
+               /* bulk continuation URB flag available from Linux 2.6.32 */
+               supports_flag_bulk_continuation = kernel_version_ge(2,6,32);
                if (supports_flag_bulk_continuation == -1) {
                        usbi_err(ctx, "error checking for bulk continuation support");
                        return LIBUSB_ERROR_OTHER;