[Toybox] [RESEND PATCH] mdev: browse /sys/block only if directory exists

[Gaël PORTAY]

When the kernel block layer is disabled, mdev terminates in error
because it cannot browse /sys/block.

It reports the following message.

	mdev: /sys/block: No such file or directory
---
 toys/pending/mdev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/toys/pending/mdev.c b/toys/pending/mdev.c
index a270e52..cab56d3 100644
--- a/toys/pending/mdev.c
+++ b/toys/pending/mdev.c
@@ -223,10 +223,12 @@ static int callback(struct dirtree *node)
 void mdev_main(void)
 {
   // Handle -s
+  struct stat st;
 
   if (toys.optflags) {
     dirtree_read("/sys/class", callback);
-    dirtree_read("/sys/block", callback);
+    if (!stat("/sys/block", &st))
+      dirtree_read("/sys/block", callback);
   } else { // hotplug support
     make_device(NULL);
   }
-- 
2.15.0