thinkpad-acpi: find ACPI video device by synthetic HID

The Linux ACPI core locates the ACPI video devices for us and marks them
with ACPI_VIDEO_HID.  Use that information to locate the video device
instead of a half-baked hunt for _BCL.

This uncouples the detection of the number of backlight brightness
levels on ThinkPads from the ACPI paths in vid_handle.

With this change, the driver should be able to always detect whether the
ThinkPad uses a 8-level or 16-level brightness scale even on newer
models for which the vid_handle paths have not been updated yet.

It will skip deactivated devices in the ACPI device tree, which is a
change in behaviour.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

1 files changed, 12 insertions, 40 deletions

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 5d6119bed00c..9d6fc4c7c08e 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -6080,13 +6080,18 @@ static struct backlight_ops ibm_backlight_data = {
 
 /* --------------------------------------------------------------------- */
 
+/*
+ * Call _BCL method of video device.  On some ThinkPads this will
+ * switch the firmware to the ACPI brightness control mode.
+ */
+
 static int __init tpacpi_query_bcl_levels(acpi_handle handle)
 {
         struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
         union acpi_object *obj;
         int rc;
 
-        if (ACPI_SUCCESS(acpi_evaluate_object(handle, NULL, NULL, &buffer))) {
+        if (ACPI_SUCCESS(acpi_evaluate_object(handle, "_BCL", NULL, &buffer))) {
                 obj = (union acpi_object *)buffer.pointer;
                 if (!obj || (obj->type != ACPI_TYPE_PACKAGE)) {
                         printk(TPACPI_ERR "Unknown _BCL data, "
@@ -6103,55 +6108,22 @@ static int __init tpacpi_query_bcl_levels(acpi_handle handle)
         return rc;
 }
 
-static acpi_status __init tpacpi_acpi_walk_find_bcl(acpi_handle handle,
-                                        u32 lvl, void *context, void **rv)
-{
-        char name[ACPI_PATH_SEGMENT_LENGTH];
-        struct acpi_buffer buffer = { sizeof(name), &name };
-
-        if (ACPI_SUCCESS(acpi_get_name(handle, ACPI_SINGLE_NAME, &buffer)) &&
-            !strncmp("_BCL", name, sizeof(name) - 1)) {
-                BUG_ON(!rv || !*rv);
-                **(int **)rv = tpacpi_query_bcl_levels(handle);
-                return AE_CTRL_TERMINATE;
-        } else {
-                return AE_OK;
-        }
-}
 
 /*
  * Returns 0 (no ACPI _BCL or _BCL invalid), or size of brightness map
  */
 static unsigned int __init tpacpi_check_std_acpi_brightness_support(void)
 {
-        int status;
+        acpi_handle video_device;
         int bcl_levels = 0;
-        void *bcl_ptr = &bcl_levels;
 
-        if (!vid_handle)
-                TPACPI_ACPIHANDLE_INIT(vid);
+        tpacpi_acpi_handle_locate("video", ACPI_VIDEO_HID, &video_device);
+        if (video_device)
+                bcl_levels = tpacpi_query_bcl_levels(video_device);
 
-        if (!vid_handle)
-                return 0;
-
-        /*
-         * Search for a _BCL method, and execute it.  This is safe on all
-         * ThinkPads, and as a side-effect, _BCL will place a Lenovo Vista
-         * BIOS in ACPI backlight control mode.  We do NOT have to care
-         * about calling the _BCL method in an enabled video device, any
-         * will do for our purposes.
-         */
+        tp_features.bright_acpimode = (bcl_levels > 0);
 
-        status = acpi_walk_namespace(ACPI_TYPE_METHOD, vid_handle, 3,
-                                     tpacpi_acpi_walk_find_bcl, NULL, NULL,
-                                     &bcl_ptr);
-
-        if (ACPI_SUCCESS(status) && bcl_levels > 2) {
-                tp_features.bright_acpimode = 1;
-                return bcl_levels - 2;
-        }
-
-        return 0;
+        return (bcl_levels > 2) ? (bcl_levels - 2) : 0;
 }
 
 /*