Commit 
b4aa0163056b ("efifb: Implement vga_default_device() (v2)") added
efifb vga_default_device() so EFI systems that do not load shadow VBIOS or
setup VGA get proper value for boot_vga PCI sysfs attribute on the
corresponding PCI device.
Xorg doesn't detect devices when boot_vga=0, e.g., on some EFI systems such
as MacBookAir2,1.  Xorg detects the GPU and finds the DRI device but then
bails out with "no devices detected".
Note: When vga_default_device() is set boot_vga PCI sysfs attribute
reflects its state.  When unset this attribute is 1 whenever
IORESOURCE_ROM_SHADOW flag is set.
With introduction of sysfb/simplefb/simpledrm efifb is getting obsolete
while having native drivers for the GPU also makes selecting sysfb/efifb
optional.
Remove the efifb implementation of vga_default_device() and initialize
vgaarb's vga_default_device() with the PCI GPU that matches boot
screen_info in pci_fixup_video().
[bhelgaas: remove unused "dev" in efifb_setup()]
Fixes: b4aa0163056b ("efifb: Implement vga_default_device() (v2)")
Tested-by: Anibal Francisco Martinez Cortina <linuxkid.zeuz@gmail.com>
Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Matthew Garrett <matthew.garrett@nebula.com>
CC: stable@vger.kernel.org	# v3.5+
 
 #include <linux/pci.h>
 #include <linux/init.h>
 #include <linux/vgaarb.h>
+#include <linux/screen_info.h>
 
 #include <asm/machvec.h>
 
                return;
        /* Maybe, this machine supports legacy memory map. */
 
+       if (!vga_default_device()) {
+               resource_size_t start, end;
+               int i;
+
+               /* Does firmware framebuffer belong to us? */
+               for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
+                       if (!(pci_resource_flags(pdev, i) & IORESOURCE_MEM))
+                               continue;
+
+                       start = pci_resource_start(pdev, i);
+                       end  = pci_resource_end(pdev, i);
+
+                       if (!start || !end)
+                               continue;
+
+                       if (screen_info.lfb_base >= start &&
+                           (screen_info.lfb_base + screen_info.lfb_size) < end)
+                               vga_set_default_device(pdev);
+               }
+       }
+
        /* Is VGA routed to us? */
        bus = pdev->bus;
        while (bus) {
 
 #define vga_readb(x) (*(x))
 #define vga_writeb(x, y) (*(y) = (x))
 
-#ifdef CONFIG_FB_EFI
-#define __ARCH_HAS_VGA_DEFAULT_DEVICE
-extern struct pci_dev *vga_default_device(void);
-extern void vga_set_default_device(struct pci_dev *pdev);
-#endif
-
 #endif /* _ASM_X86_VGA_H */
 
        struct pci_bus *bus;
        u16 config;
 
+       if (!vga_default_device()) {
+               resource_size_t start, end;
+               int i;
+
+               /* Does firmware framebuffer belong to us? */
+               for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
+                       if (!(pci_resource_flags(pdev, i) & IORESOURCE_MEM))
+                               continue;
+
+                       start = pci_resource_start(pdev, i);
+                       end  = pci_resource_end(pdev, i);
+
+                       if (!start || !end)
+                               continue;
+
+                       if (screen_info.lfb_base >= start &&
+                           (screen_info.lfb_base + screen_info.lfb_size) < end)
+                               vga_set_default_device(pdev);
+               }
+       }
+
        /* Is VGA routed to us? */
        bus = pdev->bus;
        while (bus) {
 
 
 static bool request_mem_succeeded = false;
 
-static struct pci_dev *default_vga;
-
 static struct fb_var_screeninfo efifb_defined = {
        .activate               = FB_ACTIVATE_NOW,
        .height                 = -1,
        .fb_imageblit   = cfb_imageblit,
 };
 
-struct pci_dev *vga_default_device(void)
-{
-       return default_vga;
-}
-
-EXPORT_SYMBOL_GPL(vga_default_device);
-
-void vga_set_default_device(struct pci_dev *pdev)
-{
-       default_vga = pdev;
-}
-
 static int efifb_setup(char *options)
 {
        char *this_opt;
        int i;
-       struct pci_dev *dev = NULL;
 
        if (options && *options) {
                while ((this_opt = strsep(&options, ",")) != NULL) {
                }
        }
 
-       for_each_pci_dev(dev) {
-               int i;
-
-               if ((dev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
-                       continue;
-
-               for (i=0; i < DEVICE_COUNT_RESOURCE; i++) {
-                       resource_size_t start, end;
-
-                       if (!(pci_resource_flags(dev, i) & IORESOURCE_MEM))
-                               continue;
-
-                       start = pci_resource_start(dev, i);
-                       end  = pci_resource_end(dev, i);
-
-                       if (!start || !end)
-                               continue;
-
-                       if (screen_info.lfb_base >= start &&
-                           (screen_info.lfb_base + screen_info.lfb_size) < end)
-                               default_vga = dev;
-               }
-       }
-
        return 0;
 }