require non-SYSFS_DEPRECATED 2.6.20+ kernel

README

@@ -9,13 +9,12 @@ Important Note:
   recommend to replace a distro's udev installation with the upstream version.
 
 Requirements:
-  - Version 2.6.19 of the Linux kernel for reliable operation of this release of
-    udev. The kernel may have a requirement on udev too, see Documentation/Changes
-    in the kernel source tree for the actual dependency.
+  - Version 2.6.20 of the Linux kernel for reliable operation of this release of
+    udev. The kernel must not use the CONFIG_SYSFS_DEPRECATED* option.
 
   - The kernel must have sysfs, unix domain sockets and networking enabled.
-    (unix domain sockets (CONFIG_UNIX) as a loadable kernel module may work,
-    but it does not make any sense - don't complain if anything goes wrong.)
+    Unix domain sockets (CONFIG_UNIX) as a loadable kernel module is not
+    supported.
 
   - The proc filesystem must be mounted on /proc/, the sysfs filesystem must
     be mounted at /sys/. No other locations are supported by udev.

udev/udevd.c

@@ -823,9 +823,10 @@ int main(int argc, char *argv[])
 		util_strlcat(path, "/class/mem/null", sizeof(path));
 		if (lstat(path, &statbuf) == 0) {
 			if (S_ISDIR(statbuf.st_mode)) {
-				const char *depr_str = "<6>udev: deprecated sysfs layout (kernel too old, "
-							"or CONFIG_SYSFS_DEPRECATED) is unsupported, some "
-							"udev features may fail\n";
+				const char *depr_str =
+					"<6>udev: deprecated sysfs layout; update the kernel or "
+					"disable CONFIG_SYSFS_DEPRECATED; some udev features will "
+					"not work correctly\n";
 
 				write(fd, depr_str, strlen(depr_str));
 			}