Sysfs: Read failures of optional attributes are not fatal

Ameya Palande reported that with some kernels, reads of such
attributes fail on some hardware. He suggested to ignore read
failures completely, but I decided to turn the errors into
warnings in such cases. At least, the user will know that something
fishy is going on.

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/sysfs.c b/lib/sysfs.c
index a16c92a..986ecc9 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -93,21 +93,28 @@ sysfs_get_string(struct pci_dev *d, char *object, char *buf, int mandatory)
   struct pci_access *a = d->access;
   int fd, n;
   char namebuf[OBJNAMELEN];
+  void (*warn)(char *msg, ...) = (mandatory ? a->error : a->warning);
 
   sysfs_obj_name(d, object, namebuf);
   fd = open(namebuf, O_RDONLY);
   if (fd < 0)
     {
-      if (mandatory)
-	a->error("Cannot open %s: %s", namebuf, strerror(errno));
+      if (mandatory || errno != ENOENT)
+	warn("Cannot open %s: %s", namebuf, strerror(errno));
       return 0;
     }
   n = read(fd, buf, OBJBUFSIZE);
   close(fd);
   if (n < 0)
-    a->error("Error reading %s: %s", namebuf, strerror(errno));
+    {
+      warn("Error reading %s: %s", namebuf, strerror(errno));
+      return 0;
+     }
   if (n >= OBJBUFSIZE)
-    a->error("Value in %s too long", namebuf);
+    {
+      warn("Value in %s too long", namebuf);
+      return 0;
+    }
   buf[n] = 0;
   return 1;
 }