thinkpad-acpi: untangle ACPI/vendor backlight selection

acpi_video_backlight_support() already tells us if ACPI is handling
backlight control through the generic ACPI handle.  It is better to just
trust it.

While at it, adjust down a printk priority, and test earlier for
brightness_enable=0.

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

2 files changed, 24 insertions, 22 deletions

diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index f6f80257addb..1565eefd6fd5 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1024,6 +1024,10 @@ ThinkPad-specific interface.  The driver will disable its native
 backlight brightness control interface if it detects that the standard
 ACPI interface is available in the ThinkPad.
 
+If you want to use the thinkpad-acpi backlight brightness control
+instead of the generic ACPI video backlight brightness control for some
+reason, you should use the acpi_backlight=vendor kernel parameter.
+
 The brightness_enable module parameter can be used to control whether
 the LCD brightness control feature will be enabled when available.
 brightness_enable=0 forces it to be disabled.  brightness_enable=1
diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 9d6fc4c7c08e..b9430e887e95 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -6216,28 +6216,6 @@ static int __init brightness_init(struct ibm_init_struct *iibm)
         if (tp_features.bright_unkfw)
                 return 1;
 
-        if (tp_features.bright_acpimode) {
-                if (acpi_video_backlight_support()) {
-                        if (brightness_enable > 1) {
-                                printk(TPACPI_NOTICE
-                                       "Standard ACPI backlight interface "
-                                       "available, not loading native one.\n");
-                                return 1;
-                        } else if (brightness_enable == 1) {
-                                printk(TPACPI_NOTICE
-                                       "Backlight control force enabled, even if standard "
-                                       "ACPI backlight interface is available\n");
-                        }
-                } else {
-                        if (brightness_enable > 1) {
-                                printk(TPACPI_NOTICE
-                                       "Standard ACPI backlight interface not "
-                                       "available, thinkpad_acpi native "
-                                       "brightness control enabled\n");
-                        }
-                }
-        }
-
         if (!brightness_enable) {
                 dbg_printk(TPACPI_DBG_INIT | TPACPI_DBG_BRGHT,
                            "brightness support disabled by "
@@ -6245,6 +6223,26 @@ static int __init brightness_init(struct ibm_init_struct *iibm)
                 return 1;
         }
 
+        if (acpi_video_backlight_support()) {
+                if (brightness_enable > 1) {
+                        printk(TPACPI_INFO
+                               "Standard ACPI backlight interface "
+                               "available, not loading native one.\n");
+                        return 1;
+                } else if (brightness_enable == 1) {
+                        printk(TPACPI_WARN
+                                "Cannot enable backlight brightness support, "
+                                "ACPI is already handling it.  Refer to the "
+                                "acpi_backlight kernel parameter\n");
+                        return 1;
+                }
+        } else if (tp_features.bright_acpimode && brightness_enable > 1) {
+                printk(TPACPI_NOTICE
+                        "Standard ACPI backlight interface not "
+                        "available, thinkpad_acpi native "
+                        "brightness control enabled\n");
+        }
+
         /*
          * Check for module parameter bogosity, note that we
          * init brightness_mode to TPACPI_BRGHT_MODE_MAX in order to be