diff -ur /home/alex/instaladores-linux/xserver/xorg-git/lib/libpciaccess/src/linux_devmem.c libpciaccess/src/linux_devmem.c
--- /home/alex/instaladores-linux/xserver/xorg-git/lib/libpciaccess/src/linux_devmem.c	2008-10-27 10:57:37.000000000 -0500
+++ libpciaccess/src/linux_devmem.c	2009-01-15 10:21:24.000000000 -0500
@@ -124,9 +124,12 @@
     else {
 	size_t bytes;
 
+        memset(buffer, 0, rom_size);
 	for (bytes = 0; bytes < rom_size; /* empty */) {
-	    const ssize_t got = pread(fd, buffer, rom_size - bytes, 
-				      rom_base + bytes);
+	    const ssize_t got = pread64(fd, 
+		(unsigned char *)buffer + bytes, 
+		rom_size - bytes, 
+		rom_base + bytes);
 	    if (got == -1) {
 		err = errno;
 		break;
diff -ur /home/alex/instaladores-linux/xserver/xorg-git/lib/libpciaccess/src/linux_sysfs.c libpciaccess/src/linux_sysfs.c
--- /home/alex/instaladores-linux/xserver/xorg-git/lib/libpciaccess/src/linux_sysfs.c	2008-10-27 10:57:37.000000000 -0500
+++ libpciaccess/src/linux_sysfs.c	2009-01-15 10:44:52.000000000 -0500
@@ -56,6 +56,7 @@
 #include "linux_devmem.h"
 
 static void pci_device_linux_sysfs_enable(struct pci_device *dev);
+static void pci_device_linux_sysfs_disable(struct pci_device *dev);
 
 static int pci_device_linux_sysfs_read_rom( struct pci_device * dev,
     void * buffer );
@@ -334,6 +335,9 @@
 	return errno;
     }
 
+    /* devices need to be enabled in order to read their ROM (refcount +1)*/
+    pci_device_linux_sysfs_enable(dev);
+
     rom_size = st.st_size;
     if ( rom_size == 0 )
 	rom_size = 0x10000;
@@ -365,6 +369,14 @@
     write( fd, "0", 1 );
 
     close( fd );
+    if (total_bytes == 0) {
+        /* Failed to read entire ROM, falling back to /dev/mem  */
+        err = pci_device_linux_devmem_read_rom(dev, buffer);
+    }
+
+    /* undo enabling of pci device (refcount -1) */
+    pci_device_linux_sysfs_disable(dev);
+
     return err;
 }
 
@@ -698,3 +710,23 @@
     write( fd, "1", 1 );
     close(fd);
 }
+
+static void pci_device_linux_sysfs_disable(struct pci_device *dev)
+{
+    char name[256];
+    int fd;
+
+    snprintf( name, 255, "%s/%04x:%02x:%02x.%1u/enable",
+	      SYS_BUS_PCI,
+	      dev->domain,
+	      dev->bus,
+	      dev->dev,
+	      dev->func );
+    
+    fd = open( name, O_RDWR );
+    if (fd == -1)
+       return;
+
+    write( fd, "0", 1 );
+    close(fd);
+}