ACPI video: if no ACPI backlight support, use vendor drivers

If an ACPI graphics device supports backlight brightness functions (cmp. with
latest ACPI spec Appendix B), let the ACPI video driver control backlight and
switch backlight control off in vendor specific ACPI drivers (asus_acpi,
thinkpad_acpi, eeepc, fujitsu_laptop, msi_laptop, sony_laptop, acer-wmi).

Currently it is possible to load above drivers and let both poke on the
brightness HW registers, the video and vendor specific ACPI drivers -> bad.

This patch provides the basic support to check for BIOS capabilities before
driver loading time. Driver specific modifications are in separate follow up
patches.

"acpi_backlight=vendor"
	Prever vendor driver over ACPI driver for backlight.
"acpi_backlight=video" (default)
	Prever ACPI driver over vendor driver for backlight.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 16 insertions, 12 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 6597c2a37c36..2097c399dd06 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -739,7 +739,8 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
                 device->cap._DSS = 1;
         }
 
-        max_level = acpi_video_init_brightness(device);
+        if (acpi_video_backlight_support())
+                max_level = acpi_video_init_brightness(device);
 
         if (device->cap._BCL && device->cap._BCM && max_level > 0) {
                 int result;
@@ -785,18 +786,21 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
                         printk(KERN_ERR PREFIX "Create sysfs link\n");
 
         }
-        if (device->cap._DCS && device->cap._DSS){
-                static int count = 0;
-                char *name;
-                name = kzalloc(MAX_NAME_LEN, GFP_KERNEL);
-                if (!name)
-                        return;
-                sprintf(name, "acpi_video%d", count++);
-                device->output_dev = video_output_register(name,
-                                NULL, device, &acpi_output_properties);
-                kfree(name);
+
+        if (acpi_video_display_switch_support()) {
+
+                if (device->cap._DCS && device->cap._DSS) {
+                        static int count;
+                        char *name;
+                        name = kzalloc(MAX_NAME_LEN, GFP_KERNEL);
+                        if (!name)
+                                return;
+                        sprintf(name, "acpi_video%d", count++);
+                        device->output_dev = video_output_register(name,
+                                        NULL, device, &acpi_output_properties);
+                        kfree(name);
+                }
         }
-        return;
 }
 
 /*