ACPI video: Don't export sysfs backlight interface if query _BCL fail

Currently the acpi video module export the backlight interface to sysfs
also if acpi_video_device_lcd_query_levels() fails to read _BLC method
(e.g.  because the method is not available).  In this case the userspace
don't know which brightness level are supported and can't set a brightness
level (echo return with: "write error: Invalid Argument").  This happend
e.g.  on a ASUS RF1 (correct supported by the asus-laptop module).

The video module should not export the backlight interface if query _BLC fail,
because you can't set anything from userspace and this make it useless.

http://bugzilla.kernel.org/show_bug.cgi?id=8375

Signed-off-by: Danny Kukawka <dkukawka@suse.de>
Acked-by: Luming Yu <luming.yu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 42 insertions, 38 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 39273dae7004..5f014d3764c8 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -559,7 +559,6 @@ acpi_video_bus_DOS(struct acpi_video_bus *video, int bios_flag, int lcd_flag)
 
 static void acpi_video_device_find_cap(struct acpi_video_device *device)
 {
-        acpi_integer status;
         acpi_handle h_dummy1;
         int i;
         u32 max_level = 0;
@@ -593,50 +592,55 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
                 device->cap._DSS = 1;
         }
 
-        status = acpi_video_device_lcd_query_levels(device, &obj);
-
-        if (obj && obj->type == ACPI_TYPE_PACKAGE && obj->package.count >= 2) {
-                int count = 0;
-                union acpi_object *o;
-
-                br = kzalloc(sizeof(*br), GFP_KERNEL);
-                if (!br) {
-                        printk(KERN_ERR "can't allocate memory\n");
-                } else {
-                        br->levels = kmalloc(obj->package.count *
-                                             sizeof *(br->levels), GFP_KERNEL);
-                        if (!br->levels)
-                                goto out;
-
-                        for (i = 0; i < obj->package.count; i++) {
-                                o = (union acpi_object *)&obj->package.
-                                    elements[i];
-                                if (o->type != ACPI_TYPE_INTEGER) {
-                                        printk(KERN_ERR PREFIX "Invalid data\n");
-                                        continue;
-                                }
-                                br->levels[count] = (u32) o->integer.value;
-                                if (br->levels[count] > max_level)
-                                        max_level = br->levels[count];
-                                count++;
-                        }
-                      out:
-                        if (count < 2) {
-                                kfree(br->levels);
-                                kfree(br);
+        if (ACPI_SUCCESS(acpi_video_device_lcd_query_levels(device, &obj))) {
+
+                if (obj->package.count >= 2) {
+                        int count = 0;
+                        union acpi_object *o;
+
+                        br = kzalloc(sizeof(*br), GFP_KERNEL);
+                        if (!br) {
+                                printk(KERN_ERR "can't allocate memory\n");
                         } else {
-                                br->count = count;
-                                device->brightness = br;
-                                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
-                                                  "found %d brightness levels\n",
-                                                  count));
+                                br->levels = kmalloc(obj->package.count *
+                                                     sizeof *(br->levels), GFP_KERNEL);
+                                if (!br->levels)
+                                        goto out;
+
+                                for (i = 0; i < obj->package.count; i++) {
+                                        o = (union acpi_object *)&obj->package.
+                                            elements[i];
+                                        if (o->type != ACPI_TYPE_INTEGER) {
+                                                printk(KERN_ERR PREFIX "Invalid data\n");
+                                                continue;
+                                        }
+                                        br->levels[count] = (u32) o->integer.value;
+
+                                        if (br->levels[count] > max_level)
+                                                max_level = br->levels[count];
+                                        count++;
+                                }
+                              out:
+                                if (count < 2) {
+                                        kfree(br->levels);
+                                        kfree(br);
+                                } else {
+                                        br->count = count;
+                                        device->brightness = br;
+                                        ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+                                                          "found %d brightness levels\n",
+                                                          count));
+                                }
                         }
                 }
+
+        } else {
+                ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Could not query available LCD brightness level\n"));
         }
 
         kfree(obj);
 
-        if (device->cap._BCL && device->cap._BCM && device->cap._BQC){
+        if (device->cap._BCL && device->cap._BCM && device->cap._BQC && max_level > 0){
                 unsigned long tmp;
                 static int count = 0;
                 char *name;