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.

diff --git a/lib/sysfs.c b/lib/sysfs.c
index a16c92a2b8980b2a9b79bdadbd92407d07fd8f95..986ecc93185aec0429961e4c8fedc815855c19f5 100644 (file)
--- 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;
 }