PCI: expose boot VGA device via sysfs.

X really would like to know which VGA device was considered the boot
device by the system. The x86 PCI fixups have support for discovering
this but we provide no way to expose it to userspace.

This adds a sysfs file per VGA class device which has the value 0 for
non the boot device or unknown, and 1 if the VGA device is the boot
device.
Acked-by: NGreg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: NDave Airlie <airlied@redhat.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pci-sysfs.c

@@ -240,6 +240,17 @@ struct device_attribute pci_dev_attrs[] = {
 	__ATTR_NULL,
 };
 
+static ssize_t
+boot_vga_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	return sprintf(buf, "%u\n",
+		!!(pdev->resource[PCI_ROM_RESOURCE].flags &
+		   IORESOURCE_ROM_SHADOW));
+}
+struct device_attribute vga_attr = __ATTR_RO(boot_vga);
+
 static ssize_t
 pci_read_config(struct kobject *kobj, struct bin_attribute *bin_attr,
 		char *buf, loff_t off, size_t count)
@@ -899,18 +910,27 @@ int __must_check pci_create_sysfs_dev_files (struct pci_dev *pdev)
 		pdev->rom_attr = attr;
 	}
 
+	if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA) {
+		retval = device_create_file(&pdev->dev, &vga_attr);
+		if (retval)
+			goto err_rom_file;
+	}
+
 	/* add platform-specific attributes */
 	retval = pcibios_add_platform_entries(pdev);
 	if (retval)
-		goto err_rom_file;
+		goto err_vga_file;
 
 	/* add sysfs entries for various capabilities */
 	retval = pci_create_capabilities_sysfs(pdev);
 	if (retval)
-		goto err_rom_file;
+		goto err_vga_file;
 
 	return 0;
 
+err_vga_file:
+	if ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
+		device_remove_file(&pdev->dev, &vga_attr);
 err_rom_file:
 	if (rom_size) {
 		sysfs_remove_bin_file(&pdev->dev.kobj, pdev->rom_attr);