[PATCH libpciaccess] Support for 32-bit domains

[Keith Busch]

On Fri, Aug 12, 2016 at 11:43:52AM +0200, Mark Kettenis wrote:
> 'struct pci_device' isn't an opaque struct, and the "documentation"
> never says that you can't build your own.  It isn't unreasonable to
> expect to be able to fill in the domain, bus, device and function
> yourself and be able to call pci_device_cfg_read().  It also means
> that code can copy a 'struct pci_device' instance around.  Code using
> the old ABI would lose the new 32-bit domain field in that case.

Hm, that also has potential memory corruption if a program allocates
their own with the older, smaller sized struct.

Unless versioning the symbols is ok (yikes!), I think ignoring these types
of domains in Linux is the simplest thing we can do. It's certainly okay
with us and infinitely better than the current behavior. :)

Here's the alternate proposal, assuming this is more readily acceptable:

  https://lists.x.org/archives/xorg-devel/2016-August/050593.html

Inlined here for convenience:

---
diff --git a/src/linux_sysfs.c b/src/linux_sysfs.c
index 6367b11..f09a832 100644
--- a/src/linux_sysfs.c
+++ b/src/linux_sysfs.c
@@ -119,18 +119,28 @@ pci_system_linux_sysfs_create( void )
 
 
 /**
- * Filter out the names "." and ".." from the scanned sysfs entries.
+ * Filter out the names "." and ".." from the scanned sysfs entries, and
+ * domains requiring 32-bits.
  *
  * \param d  Directory entry being processed by \c scandir.
  *
  * \return
- * Zero if the entry name matches either "." or "..", non-zero otherwise.
+ * Zero if the entry name matches either "." or "..", or the domain requires
+ * 32 bits, non-zero otherwise.
  *
  * \sa scandir, populate_entries
  */
 static int
 scan_sys_pci_filter( const struct dirent * d )
 {
+    if (d->d_name[0] != '.') {
+        unsigned dom = 0;
+
+        sscanf(d->d_name, "%x:", &dom);
+        if (dom > USHRT_MAX)
+            return 0;
+    }
+
     return !((strcmp( d->d_name, "." ) == 0)
 	     || (strcmp( d->d_name, ".." ) == 0));
 }
--