backlight: add backlight type

There may be multiple ways of controlling the backlight on a given
machine.  Allow drivers to expose the type of interface they are
providing, making it possible for userspace to make appropriate policy
decisions.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

59 files changed, 111 insertions, 2 deletions

diff --git a/Documentation/ABI/stable/sysfs-class-backlight b/Documentation/ABI/stable/sysfs-class-backlight
index 4d637e1c4ff7..70302f370e7e 100644
--- a/Documentation/ABI/stable/sysfs-class-backlight
+++ b/Documentation/ABI/stable/sysfs-class-backlight
@@ -34,3 +34,23 @@ Contact:	Richard Purdie <rpurdie@rpsys.net>
 Description:
                 Maximum brightness for <backlight>.
 Users:          HAL
+
+What:           /sys/class/backlight/<backlight>/type
+Date:           September 2010
+KernelVersion:  2.6.37
+Contact:        Matthew Garrett <mjg@redhat.com>
+Description:
+                The type of interface controlled by <backlight>.
+                "firmware": The driver uses a standard firmware interface
+                "platform": The driver uses a platform-specific interface
+                "raw": The driver controls hardware registers directly
+
+                In the general case, when multiple backlight
+                interfaces are available for a single device, firmware
+                control should be preferred to platform control should
+                be preferred to raw control. Using a firmware
+                interface reduces the probability of confusion with
+                the hardware and the OS independently updating the
+                backlight state. Platform interfaces are mostly a
+                holdover from pre-standardisation of firmware
+                interfaces.
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 90f8f7676d1f..a9eec8c95a1f 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -795,6 +795,7 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
                 count++;
 
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_FIRMWARE;
                 props.max_brightness = device->brightness->count - 3;
                 device->backlight = backlight_device_register(name, NULL, device,
                                                               &acpi_backlight_ops,
diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
index d3a9c6e02477..18d7bcc54ce0 100644
--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
+++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
@@ -98,6 +98,7 @@ static int nouveau_nv40_backlight_init(struct drm_device *dev)
                 return 0;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 31;
         bd = backlight_device_register("nv_backlight", &dev->pdev->dev, dev,
                                        &nv40_bl_ops, &props);
@@ -121,6 +122,7 @@ static int nouveau_nv50_backlight_init(struct drm_device *dev)
                 return 0;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 1025;
         bd = backlight_device_register("nv_backlight", &dev->pdev->dev, dev,
                                        &nv50_bl_ops, &props);
diff --git a/drivers/hid/hid-picolcd.c b/drivers/hid/hid-picolcd.c
index de9cf21b3494..657da5a3d5c6 100644
--- a/drivers/hid/hid-picolcd.c
+++ b/drivers/hid/hid-picolcd.c
@@ -944,6 +944,7 @@ static int picolcd_init_backlight(struct picolcd_data *data, struct hid_report *
         }
 
         memset(&props, 0, sizeof(props));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 0xff;
         bdev = backlight_device_register(dev_name(dev), dev, data,
                         &picolcd_blops, &props);
diff --git a/drivers/macintosh/via-pmu-backlight.c b/drivers/macintosh/via-pmu-backlight.c
index ade1e656bfb2..b1d91170ded0 100644
--- a/drivers/macintosh/via-pmu-backlight.c
+++ b/drivers/macintosh/via-pmu-backlight.c
@@ -163,6 +163,7 @@ void __init pmu_backlight_init()
         snprintf(name, sizeof(name), "pmubl");
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, NULL, NULL, &pmu_backlight_data,
                                        &props);
diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index ad3d099bf5c1..c9784705f6ac 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -1031,6 +1031,7 @@ static int __devinit acer_backlight_init(struct device *dev)
         struct backlight_device *bd;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = max_brightness;
         bd = backlight_device_register("acer-wmi", dev, NULL, &acer_bl_ops,
                                        &props);
diff --git a/drivers/platform/x86/asus-laptop.c b/drivers/platform/x86/asus-laptop.c
index f3aa6a7fdab6..5a6f7d7575d6 100644
--- a/drivers/platform/x86/asus-laptop.c
+++ b/drivers/platform/x86/asus-laptop.c
@@ -667,6 +667,7 @@ static int asus_backlight_init(struct asus_laptop *asus)
 
         memset(&props, 0, sizeof(struct backlight_properties));
         props.max_brightness = 15;
+        props.type = BACKLIGHT_PLATFORM;
 
         bd = backlight_device_register(ASUS_LAPTOP_FILE,
                                        &asus->platform_device->dev, asus,
diff --git a/drivers/platform/x86/asus_acpi.c b/drivers/platform/x86/asus_acpi.c
index fe495939c307..f503607c0645 100644
--- a/drivers/platform/x86/asus_acpi.c
+++ b/drivers/platform/x86/asus_acpi.c
@@ -1507,6 +1507,7 @@ static int __init asus_acpi_init(void)
         }
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = 15;
         asus_backlight_device = backlight_device_register("asus", NULL, NULL,
                                                           &asus_backlight_data,
diff --git a/drivers/platform/x86/classmate-laptop.c b/drivers/platform/x86/classmate-laptop.c
index 911135425224..94f93b621d7b 100644
--- a/drivers/platform/x86/classmate-laptop.c
+++ b/drivers/platform/x86/classmate-laptop.c
@@ -564,6 +564,7 @@ static int cmpc_ipml_add(struct acpi_device *acpi)
                 return -ENOMEM;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = 7;
         ipml->bd = backlight_device_register("cmpc_bl", &acpi->dev,
                                              acpi->handle, &cmpc_bl_ops,
diff --git a/drivers/platform/x86/compal-laptop.c b/drivers/platform/x86/compal-laptop.c
index 034572b980c9..eb95878fa583 100644
--- a/drivers/platform/x86/compal-laptop.c
+++ b/drivers/platform/x86/compal-laptop.c
@@ -970,6 +970,7 @@ static int __init compal_init(void)
         if (!acpi_video_backlight_support()) {
                 struct backlight_properties props;
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = BACKLIGHT_LEVEL_MAX;
                 compalbl_device = backlight_device_register(DRIVER_NAME,
                                                             NULL, NULL,
diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index ad24ef36f9f7..de301aa8e5c3 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -671,6 +671,7 @@ static int __init dell_init(void)
         if (max_intensity) {
                 struct backlight_properties props;
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = max_intensity;
                 dell_backlight_device = backlight_device_register("dell_backlight",
                                                                   &platform_device->dev,
diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
index 49d9ad708f89..6605beac0d0e 100644
--- a/drivers/platform/x86/eeepc-laptop.c
+++ b/drivers/platform/x86/eeepc-laptop.c
@@ -1147,6 +1147,7 @@ static int eeepc_backlight_init(struct eeepc_laptop *eeepc)
         struct backlight_device *bd;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = 15;
         bd = backlight_device_register(EEEPC_LAPTOP_FILE,
                                        &eeepc->platform_device->dev, eeepc,
diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
index 95e3b0948e9c..493054c2dbe1 100644
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -1128,6 +1128,7 @@ static int __init fujitsu_init(void)
 
                 memset(&props, 0, sizeof(struct backlight_properties));
                 max_brightness = fujitsu->max_brightness;
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = max_brightness - 1;
                 fujitsu->bl_device = backlight_device_register("fujitsu-laptop",
                                                                NULL, NULL,
diff --git a/drivers/platform/x86/msi-laptop.c b/drivers/platform/x86/msi-laptop.c
index 7e9bb6df9d39..142d38579314 100644
--- a/drivers/platform/x86/msi-laptop.c
+++ b/drivers/platform/x86/msi-laptop.c
@@ -804,6 +804,7 @@ static int __init msi_init(void)
         } else {
                 struct backlight_properties props;
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = MSI_LCD_LEVEL_MAX - 1;
                 msibl_device = backlight_device_register("msi-laptop-bl", NULL,
                                                          NULL, &msibl_ops,
diff --git a/drivers/platform/x86/msi-wmi.c b/drivers/platform/x86/msi-wmi.c
index 35278ad7e628..d5419c9ec07a 100644
--- a/drivers/platform/x86/msi-wmi.c
+++ b/drivers/platform/x86/msi-wmi.c
@@ -254,6 +254,7 @@ static int __init msi_wmi_init(void)
         if (!acpi_video_backlight_support()) {
                 struct backlight_properties props;
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = ARRAY_SIZE(backlight_map) - 1;
                 backlight = backlight_device_register(DRV_NAME, NULL, NULL,
                                                       &msi_backlight_ops,
diff --git a/drivers/platform/x86/panasonic-laptop.c b/drivers/platform/x86/panasonic-laptop.c
index cc1e0ba104d7..05be30ee158b 100644
--- a/drivers/platform/x86/panasonic-laptop.c
+++ b/drivers/platform/x86/panasonic-laptop.c
@@ -602,6 +602,7 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
         }
         /* initialize backlight */
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = pcc->sinf[SINF_AC_MAX_BRIGHT];
         pcc->backlight = backlight_device_register("panasonic", NULL, pcc,
                                                    &pcc_backlight_ops, &props);
diff --git a/drivers/platform/x86/sony-laptop.c b/drivers/platform/x86/sony-laptop.c
index 5e83370b0812..13d8d63bcca9 100644
--- a/drivers/platform/x86/sony-laptop.c
+++ b/drivers/platform/x86/sony-laptop.c
@@ -1305,8 +1305,9 @@ static int sony_nc_add(struct acpi_device *device)
                        "controlled by ACPI video driver\n");
         } else if (ACPI_SUCCESS(acpi_get_handle(sony_nc_acpi_handle, "GBRT",
                                                 &handle))) {
-                                                        struct backlight_properties props;
+                struct backlight_properties props;
                 memset(&props, 0, sizeof(struct backlight_properties));
+                props.type = BACKLIGHT_PLATFORM;
                 props.max_brightness = SONY_MAX_BRIGHTNESS - 1;
                 sony_backlight_device = backlight_device_register("sony", NULL,
                                                                   NULL,
diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index eb9922385ef8..947bdcaa0ce9 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -6307,6 +6307,7 @@ static int __init brightness_init(struct ibm_init_struct *iibm)
                 return 1;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = bright_maxlvl;
         props.brightness = b & TP_EC_BACKLIGHT_LVLMSK;
         ibm_backlight_device = backlight_device_register(TPACPI_BACKLIGHT_DEV_NAME,
diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
index 209cced786c6..63f42a22e102 100644
--- a/drivers/platform/x86/toshiba_acpi.c
+++ b/drivers/platform/x86/toshiba_acpi.c
@@ -1018,6 +1018,7 @@ static int __init toshiba_acpi_init(void)
                 create_toshiba_proc_entries();
         }
 
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = HCI_LCD_BRIGHTNESS_LEVELS - 1;
         toshiba_backlight_device = backlight_device_register("toshiba",
                                                              &toshiba_acpi.p_dev->dev,
diff --git a/drivers/staging/olpc_dcon/olpc_dcon.c b/drivers/staging/olpc_dcon/olpc_dcon.c
index b90c2cf3e247..750fe5045efa 100644
--- a/drivers/staging/olpc_dcon/olpc_dcon.c
+++ b/drivers/staging/olpc_dcon/olpc_dcon.c
@@ -574,6 +574,7 @@ static const struct backlight_ops dcon_bl_ops = {
 
 static struct backlight_properties dcon_bl_props = {
         .max_brightness = 15,
+        .type = BACKLIGHT_RAW,
         .power = FB_BLANK_UNBLANK,
 };
 
diff --git a/drivers/staging/samsung-laptop/samsung-laptop.c b/drivers/staging/samsung-laptop/samsung-laptop.c
index 6607a89ccb4b..25294462b8b6 100644
--- a/drivers/staging/samsung-laptop/samsung-laptop.c
+++ b/drivers/staging/samsung-laptop/samsung-laptop.c
@@ -781,6 +781,7 @@ static int __init samsung_init(void)
 
         /* create a backlight device to talk to this one */
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = sabi_config->max_brightness;
         backlight_device = backlight_device_register("samsung", &sdev->dev,
                                                      NULL, &backlight_ops,
diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c
index 1fa6ce3e4a23..68ab460a735c 100644
--- a/drivers/usb/misc/appledisplay.c
+++ b/drivers/usb/misc/appledisplay.c
@@ -282,6 +282,7 @@ static int appledisplay_probe(struct usb_interface *iface,
         snprintf(bl_name, sizeof(bl_name), "appledisplay%d",
                 atomic_inc_return(&count_displays) - 1);
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 0xff;
         pdata->bd = backlight_device_register(bl_name, NULL, pdata,
                                               &appledisplay_bl_data, &props);
diff --git a/drivers/video/atmel_lcdfb.c b/drivers/video/atmel_lcdfb.c
index bac163450216..4b4e8dadd6b2 100644
--- a/drivers/video/atmel_lcdfb.c
+++ b/drivers/video/atmel_lcdfb.c
@@ -127,6 +127,7 @@ static void init_backlight(struct atmel_lcdfb_info *sinfo)
                 return;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 0xff;
         bl = backlight_device_register("backlight", &sinfo->pdev->dev, sinfo,
                                        &atmel_lcdc_bl_ops, &props);
diff --git a/drivers/video/aty/aty128fb.c b/drivers/video/aty/aty128fb.c
index 4cb6a576c567..b0b2ac335347 100644
--- a/drivers/video/aty/aty128fb.c
+++ b/drivers/video/aty/aty128fb.c
@@ -1818,6 +1818,7 @@ static void aty128_bl_init(struct aty128fb_par *par)
         snprintf(name, sizeof(name), "aty128bl%d", info->node);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, info->dev, par, &aty128_bl_data,
                                        &props);
diff --git a/drivers/video/aty/atyfb_base.c b/drivers/video/aty/atyfb_base.c
index 94e293fce1d2..d437b3daf1f5 100644
--- a/drivers/video/aty/atyfb_base.c
+++ b/drivers/video/aty/atyfb_base.c
@@ -2241,6 +2241,7 @@ static void aty_bl_init(struct atyfb_par *par)
         snprintf(name, sizeof(name), "atybl%d", info->node);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, info->dev, par, &aty_bl_data,
                                        &props);
diff --git a/drivers/video/aty/radeon_backlight.c b/drivers/video/aty/radeon_backlight.c
index 9b811ddbce83..db572df7e1ef 100644
--- a/drivers/video/aty/radeon_backlight.c
+++ b/drivers/video/aty/radeon_backlight.c
@@ -158,6 +158,7 @@ void radeonfb_bl_init(struct radeonfb_info *rinfo)
         snprintf(name, sizeof(name), "radeonbl%d", rinfo->info->node);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, rinfo->info->dev, pdata,
                                        &radeon_bl_data, &props);
diff --git a/drivers/video/backlight/88pm860x_bl.c b/drivers/video/backlight/88pm860x_bl.c
index b224396b86d5..e59623a15f3f 100644
--- a/drivers/video/backlight/88pm860x_bl.c
+++ b/drivers/video/backlight/88pm860x_bl.c
@@ -227,6 +227,7 @@ static int pm860x_backlight_probe(struct platform_device *pdev)
         }
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = MAX_BRIGHTNESS;
         bl = backlight_device_register(name, &pdev->dev, data,
                                         &pm860x_backlight_ops, &props);
diff --git a/drivers/video/backlight/adp5520_bl.c b/drivers/video/backlight/adp5520_bl.c
index 9f436e014f85..af3119707dbf 100644
--- a/drivers/video/backlight/adp5520_bl.c
+++ b/drivers/video/backlight/adp5520_bl.c
@@ -303,6 +303,7 @@ static int __devinit adp5520_bl_probe(struct platform_device *pdev)
         mutex_init(&data->lock);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = ADP5020_MAX_BRIGHTNESS;
         bl = backlight_device_register(pdev->name, data->master, data,
                                        &adp5520_bl_ops, &props);
diff --git a/drivers/video/backlight/adp8860_bl.c b/drivers/video/backlight/adp8860_bl.c
index 734c650a47c4..d2a96a421ffd 100644
--- a/drivers/video/backlight/adp8860_bl.c
+++ b/drivers/video/backlight/adp8860_bl.c
@@ -709,6 +709,7 @@ static int __devinit adp8860_probe(struct i2c_client *client,
         i2c_set_clientdata(client, data);
 
         memset(&props, 0, sizeof(props));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = ADP8860_MAX_BRIGHTNESS;
 
         mutex_init(&data->lock);
diff --git a/drivers/video/backlight/adx_bl.c b/drivers/video/backlight/adx_bl.c
index fe9af129c5dd..c861c41af442 100644
--- a/drivers/video/backlight/adx_bl.c
+++ b/drivers/video/backlight/adx_bl.c
@@ -104,6 +104,7 @@ static int __devinit adx_backlight_probe(struct platform_device *pdev)
         }
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 0xff;
         bldev = backlight_device_register(dev_name(&pdev->dev), &pdev->dev,
                                           bl, &adx_backlight_ops, &props);
diff --git a/drivers/video/backlight/atmel-pwm-bl.c b/drivers/video/backlight/atmel-pwm-bl.c
index e6a66dab088c..0443a4f71858 100644
--- a/drivers/video/backlight/atmel-pwm-bl.c
+++ b/drivers/video/backlight/atmel-pwm-bl.c
@@ -168,6 +168,7 @@ static int atmel_pwm_bl_probe(struct platform_device *pdev)
         }
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
         bldev = backlight_device_register("atmel-pwm-bl", &pdev->dev, pwmbl,
                                           &atmel_pwm_bl_ops, &props);
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 08703299ef61..80d292fb92d8 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -19,6 +19,12 @@
 #include <asm/backlight.h>
 #endif
 
+static const char const *backlight_types[] = {
+        [BACKLIGHT_RAW] = "raw",
+        [BACKLIGHT_PLATFORM] = "platform",
+        [BACKLIGHT_FIRMWARE] = "firmware",
+};
+
 #if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
                            defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
 /* This callback gets called when something important happens inside a
@@ -169,6 +175,14 @@ static ssize_t backlight_store_brightness(struct device *dev,
         return rc;
 }
 
+static ssize_t backlight_show_type(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct backlight_device *bd = to_backlight_device(dev);
+
+        return sprintf(buf, "%s\n", backlight_types[bd->props.type]);
+}
+
 static ssize_t backlight_show_max_brightness(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
@@ -234,6 +248,7 @@ static struct device_attribute bl_device_attributes[] = {
         __ATTR(actual_brightness, 0444, backlight_show_actual_brightness,
                      NULL),
         __ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL),
+        __ATTR(type, 0444, backlight_show_type, NULL),
         __ATTR_NULL,
 };
 
@@ -292,9 +307,16 @@ struct backlight_device *backlight_device_register(const char *name,
         dev_set_drvdata(&new_bd->dev, devdata);
 
         /* Set default properties */
-        if (props)
+        if (props) {
                 memcpy(&new_bd->props, props,
                        sizeof(struct backlight_properties));
+                if (props->type <= 0 || props->type >= BACKLIGHT_TYPE_MAX) {
+                        WARN(1, "%s: invalid backlight type", name);
+                        new_bd->props.type = BACKLIGHT_RAW;
+                }
+        } else {
+                new_bd->props.type = BACKLIGHT_RAW;
+        }
 
         rc = device_register(&new_bd->dev);
         if (rc) {
diff --git a/drivers/video/backlight/corgi_lcd.c b/drivers/video/backlight/corgi_lcd.c
index 1e71c35083bb..af6098396fe6 100644
--- a/drivers/video/backlight/corgi_lcd.c
+++ b/drivers/video/backlight/corgi_lcd.c
@@ -562,6 +562,7 @@ static int __devinit corgi_lcd_probe(struct spi_device *spi)
         lcd->mode = (pdata) ? pdata->init_mode : CORGI_LCD_MODE_VGA;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = pdata->max_intensity;
         lcd->bl_dev = backlight_device_register("corgi_bl", &spi->dev, lcd,
                                                 &corgi_bl_ops, &props);
diff --git a/drivers/video/backlight/cr_bllcd.c b/drivers/video/backlight/cr_bllcd.c
index 397d15eb1ea8..6c8c54041fae 100644
--- a/drivers/video/backlight/cr_bllcd.c
+++ b/drivers/video/backlight/cr_bllcd.c
@@ -193,6 +193,7 @@ static int cr_backlight_probe(struct platform_device *pdev)
         }
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         bdp = backlight_device_register("cr-backlight", &pdev->dev, NULL,
                                         &cr_backlight_ops, &props);
         if (IS_ERR(bdp)) {
diff --git a/drivers/video/backlight/da903x_bl.c b/drivers/video/backlight/da903x_bl.c
index 87659ed79bd7..62043f12a5a4 100644
--- a/drivers/video/backlight/da903x_bl.c
+++ b/drivers/video/backlight/da903x_bl.c
@@ -136,6 +136,7 @@ static int da903x_backlight_probe(struct platform_device *pdev)
                 da903x_write(data->da903x_dev, DA9034_WLED_CONTROL2,
                                 DA9034_WLED_ISET(pdata->output_current));
 
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = max_brightness;
         bl = backlight_device_register(pdev->name, data->da903x_dev, data,
                                        &da903x_backlight_ops, &props);
diff --git a/drivers/video/backlight/ep93xx_bl.c b/drivers/video/backlight/ep93xx_bl.c
index b0cc49184803..9f1e389d51d2 100644
--- a/drivers/video/backlight/ep93xx_bl.c
+++ b/drivers/video/backlight/ep93xx_bl.c
@@ -87,6 +87,7 @@ static int __init ep93xxbl_probe(struct platform_device *dev)
         ep93xxbl->mmio = EP93XX_RASTER_BRIGHTNESS;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = EP93XX_MAX_BRIGHT;
         bl = backlight_device_register(dev->name, &dev->dev, ep93xxbl,
                                        &ep93xxbl_ops, &props);
diff --git a/drivers/video/backlight/generic_bl.c b/drivers/video/backlight/generic_bl.c
index 312ca619735d..8c6befd65a33 100644
--- a/drivers/video/backlight/generic_bl.c
+++ b/drivers/video/backlight/generic_bl.c
@@ -91,6 +91,7 @@ static int genericbl_probe(struct platform_device *pdev)
                 name = machinfo->name;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = machinfo->max_intensity;
         bd = backlight_device_register(name, &pdev->dev, NULL, &genericbl_ops,
                                        &props);
diff --git a/drivers/video/backlight/hp680_bl.c b/drivers/video/backlight/hp680_bl.c
index 267d23f8d645..38aa00272141 100644
--- a/drivers/video/backlight/hp680_bl.c
+++ b/drivers/video/backlight/hp680_bl.c
@@ -109,6 +109,7 @@ static int __devinit hp680bl_probe(struct platform_device *pdev)
         struct backlight_device *bd;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = HP680_MAX_INTENSITY;
         bd = backlight_device_register("hp680-bl", &pdev->dev, NULL,
                                        &hp680bl_ops, &props);
diff --git a/drivers/video/backlight/jornada720_bl.c b/drivers/video/backlight/jornada720_bl.c
index 2f177b3a4885..40e4fa8fcf92 100644
--- a/drivers/video/backlight/jornada720_bl.c
+++ b/drivers/video/backlight/jornada720_bl.c
@@ -106,6 +106,7 @@ static int jornada_bl_probe(struct platform_device *pdev)
         struct backlight_device *bd;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = BL_MAX_BRIGHT;
         bd = backlight_device_register(S1D_DEVICENAME, &pdev->dev, NULL,
                                        &jornada_bl_ops, &props);
diff --git a/drivers/video/backlight/kb3886_bl.c b/drivers/video/backlight/kb3886_bl.c
index f439a8632287..72dd5556a35b 100644
--- a/drivers/video/backlight/kb3886_bl.c
+++ b/drivers/video/backlight/kb3886_bl.c
@@ -149,6 +149,7 @@ static int kb3886bl_probe(struct platform_device *pdev)
                 machinfo->limit_mask = -1;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = machinfo->max_intensity;
         kb3886_backlight_device = backlight_device_register("kb3886-bl",
                                                             &pdev->dev, NULL,
diff --git a/drivers/video/backlight/locomolcd.c b/drivers/video/backlight/locomolcd.c
index d2f59015d517..bbca3127071e 100644
--- a/drivers/video/backlight/locomolcd.c
+++ b/drivers/video/backlight/locomolcd.c
@@ -184,6 +184,7 @@ static int locomolcd_probe(struct locomo_dev *ldev)
         local_irq_restore(flags);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 4;
         locomolcd_bl_device = backlight_device_register("locomo-bl",
                                                         &ldev->dev, NULL,
diff --git a/drivers/video/backlight/max8925_bl.c b/drivers/video/backlight/max8925_bl.c
index 209acc105cbc..07e8e273ced0 100644
--- a/drivers/video/backlight/max8925_bl.c
+++ b/drivers/video/backlight/max8925_bl.c
@@ -136,6 +136,7 @@ static int __devinit max8925_backlight_probe(struct platform_device *pdev)
         data->current_brightness = 0;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = MAX_BRIGHTNESS;
         bl = backlight_device_register(name, &pdev->dev, data,
                                         &max8925_backlight_ops, &props);
diff --git a/drivers/video/backlight/mbp_nvidia_bl.c b/drivers/video/backlight/mbp_nvidia_bl.c
index 1485f7345f49..74c33944aa86 100644
--- a/drivers/video/backlight/mbp_nvidia_bl.c
+++ b/drivers/video/backlight/mbp_nvidia_bl.c
@@ -367,6 +367,7 @@ static int __init mbp_init(void)
                 return -ENXIO;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = 15;
         mbp_backlight_device = backlight_device_register("mbp_backlight", NULL,
                                                          NULL,
diff --git a/drivers/video/backlight/omap1_bl.c b/drivers/video/backlight/omap1_bl.c
index d3bc56296c8d..08d26a72394c 100644
--- a/drivers/video/backlight/omap1_bl.c
+++ b/drivers/video/backlight/omap1_bl.c
@@ -146,6 +146,7 @@ static int omapbl_probe(struct platform_device *pdev)
                 return -ENOMEM;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = OMAPBL_MAX_INTENSITY;
         dev = backlight_device_register("omap-bl", &pdev->dev, bl, &omapbl_ops,
                                         &props);
diff --git a/drivers/video/backlight/pcf50633-backlight.c b/drivers/video/backlight/pcf50633-backlight.c
index 3c424f7efdcc..ef5628d60563 100644
--- a/drivers/video/backlight/pcf50633-backlight.c
+++ b/drivers/video/backlight/pcf50633-backlight.c
@@ -112,6 +112,7 @@ static int __devinit pcf50633_bl_probe(struct platform_device *pdev)
         if (!pcf_bl)
                 return -ENOMEM;
 
+        bl_props.type = BACKLIGHT_RAW;
         bl_props.max_brightness = 0x3f;
         bl_props.power = FB_BLANK_UNBLANK;
 
diff --git a/drivers/video/backlight/progear_bl.c b/drivers/video/backlight/progear_bl.c
index 809278c90738..6af183d6465e 100644
--- a/drivers/video/backlight/progear_bl.c
+++ b/drivers/video/backlight/progear_bl.c
@@ -84,6 +84,7 @@ static int progearbl_probe(struct platform_device *pdev)
         pci_write_config_byte(sb_dev, SB_MPS1, temp | 0x20);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = HW_LEVEL_MAX - HW_LEVEL_MIN;
         progear_backlight_device = backlight_device_register("progear-bl",
                                                              &pdev->dev, NULL,
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 21866ec69656..2c2a2c703c14 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -108,6 +108,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
                 dev_dbg(&pdev->dev, "got pwm for backlight\n");
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = data->max_brightness;
         bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
                                        &pwm_backlight_ops, &props);
diff --git a/drivers/video/backlight/s6e63m0.c b/drivers/video/backlight/s6e63m0.c
index 5927db0da999..322040f686c2 100644
--- a/drivers/video/backlight/s6e63m0.c
+++ b/drivers/video/backlight/s6e63m0.c
@@ -778,6 +778,7 @@ static int __devinit s6e63m0_probe(struct spi_device *spi)
 
         bd->props.max_brightness = MAX_BRIGHTNESS;
         bd->props.brightness = MAX_BRIGHTNESS;
+        bd->props.type = BACKLIGHT_RAW;
         lcd->bd = bd;
 
         /*
diff --git a/drivers/video/backlight/tosa_bl.c b/drivers/video/backlight/tosa_bl.c
index 2a04b382ec48..425a7365470b 100644
--- a/drivers/video/backlight/tosa_bl.c
+++ b/drivers/video/backlight/tosa_bl.c
@@ -102,6 +102,7 @@ static int __devinit tosa_bl_probe(struct i2c_client *client,
         data->i2c = client;
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 512 - 1;
         data->bl = backlight_device_register("tosa-bl", &client->dev, data,
                                              &bl_ops, &props);
diff --git a/drivers/video/backlight/wm831x_bl.c b/drivers/video/backlight/wm831x_bl.c
index 08fd87f3aecc..d4c6eb248ff9 100644
--- a/drivers/video/backlight/wm831x_bl.c
+++ b/drivers/video/backlight/wm831x_bl.c
@@ -193,6 +193,7 @@ static int wm831x_backlight_probe(struct platform_device *pdev)
         data->current_brightness = 0;
         data->isink_reg = isink_reg;
 
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = max_isel;
         bl = backlight_device_register("wm831x", &pdev->dev, data,
                                        &wm831x_backlight_ops, &props);
diff --git a/drivers/video/bf54x-lq043fb.c b/drivers/video/bf54x-lq043fb.c
index e7d0f525041e..2464b910b590 100644
--- a/drivers/video/bf54x-lq043fb.c
+++ b/drivers/video/bf54x-lq043fb.c
@@ -649,6 +649,7 @@ static int __devinit bfin_bf54x_probe(struct platform_device *pdev)
         }
 #ifndef NO_BL_SUPPORT
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 255;
         bl_dev = backlight_device_register("bf54x-bl", NULL, NULL,
                                            &bfin_lq043fb_bl_ops, &props);
diff --git a/drivers/video/bfin-t350mcqb-fb.c b/drivers/video/bfin-t350mcqb-fb.c
index 3cf77676947c..d8de29f0dd8d 100644
--- a/drivers/video/bfin-t350mcqb-fb.c
+++ b/drivers/video/bfin-t350mcqb-fb.c
@@ -545,6 +545,7 @@ static int __devinit bfin_t350mcqb_probe(struct platform_device *pdev)
         }
 #ifndef NO_BL_SUPPORT
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = 255;
         bl_dev = backlight_device_register("bf52x-bl", NULL, NULL,
                                            &bfin_lq043fb_bl_ops, &props);
diff --git a/drivers/video/imxfb.c b/drivers/video/imxfb.c
index 69bd4a581d4a..ef72cb483834 100644
--- a/drivers/video/imxfb.c
+++ b/drivers/video/imxfb.c
@@ -499,6 +499,7 @@ static void imxfb_init_backlight(struct imxfb_info *fbi)
 
         memset(&props, 0, sizeof(struct backlight_properties));
         props.max_brightness = 0xff;
+        props.type = BACKLIGHT_RAW;
         writel(fbi->pwmr, fbi->regs + LCDC_PWMR);
 
         bl = backlight_device_register("imxfb-bl", &fbi->pdev->dev, fbi,
diff --git a/drivers/video/nvidia/nv_backlight.c b/drivers/video/nvidia/nv_backlight.c
index 6aac6d1b937b..8471008aa6ff 100644
--- a/drivers/video/nvidia/nv_backlight.c
+++ b/drivers/video/nvidia/nv_backlight.c
@@ -111,6 +111,7 @@ void nvidia_bl_init(struct nvidia_par *par)
         snprintf(name, sizeof(name), "nvidiabl%d", info->node);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, info->dev, par, &nvidia_bl_ops,
                                        &props);
diff --git a/drivers/video/omap2/displays/panel-acx565akm.c b/drivers/video/omap2/displays/panel-acx565akm.c
index e77310653207..7e04c921aa2a 100644
--- a/drivers/video/omap2/displays/panel-acx565akm.c
+++ b/drivers/video/omap2/displays/panel-acx565akm.c
@@ -534,6 +534,7 @@ static int acx_panel_probe(struct omap_dss_device *dssdev)
 
         props.fb_blank = FB_BLANK_UNBLANK;
         props.power = FB_BLANK_UNBLANK;
+        props.type = BACKLIGHT_RAW;
 
         bldev = backlight_device_register("acx565akm", &md->spi->dev,
                         md, &acx565akm_bl_ops, &props);
diff --git a/drivers/video/omap2/displays/panel-sharp-ls037v7dw01.c b/drivers/video/omap2/displays/panel-sharp-ls037v7dw01.c
index 9a138f650e05..d2b35d2df2a6 100644
--- a/drivers/video/omap2/displays/panel-sharp-ls037v7dw01.c
+++ b/drivers/video/omap2/displays/panel-sharp-ls037v7dw01.c
@@ -99,6 +99,7 @@ static int sharp_ls_panel_probe(struct omap_dss_device *dssdev)
 
         memset(&props, 0, sizeof(struct backlight_properties));
         props.max_brightness = dssdev->max_backlight_level;
+        props.type = BACKLIGHT_RAW;
 
         bl = backlight_device_register("sharp-ls", &dssdev->dev, dssdev,
                         &sharp_ls_bl_ops, &props);
diff --git a/drivers/video/omap2/displays/panel-taal.c b/drivers/video/omap2/displays/panel-taal.c
index 61026f96ad20..c74e8b778ba1 100644
--- a/drivers/video/omap2/displays/panel-taal.c
+++ b/drivers/video/omap2/displays/panel-taal.c
@@ -729,6 +729,8 @@ static int taal_probe(struct omap_dss_device *dssdev)
                 props.max_brightness = 255;
         else
                 props.max_brightness = 127;
+
+        props.type = BACKLIGHT_RAW;
         bldev = backlight_device_register("taal", &dssdev->dev, dssdev,
                                           &taal_bl_ops, &props);
         if (IS_ERR(bldev)) {
diff --git a/drivers/video/riva/fbdev.c b/drivers/video/riva/fbdev.c
index da388186d617..d8ab7be4fd6b 100644
--- a/drivers/video/riva/fbdev.c
+++ b/drivers/video/riva/fbdev.c
@@ -355,6 +355,7 @@ static void riva_bl_init(struct riva_par *par)
         snprintf(name, sizeof(name), "rivabl%d", info->node);
 
         memset(&props, 0, sizeof(struct backlight_properties));
+        props.type = BACKLIGHT_RAW;
         props.max_brightness = FB_BACKLIGHT_LEVELS - 1;
         bd = backlight_device_register(name, info->dev, par, &riva_bl_ops,
                                        &props);
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 4a3d52e545e1..5ffc6dda4675 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -32,6 +32,13 @@ enum backlight_update_reason {
         BACKLIGHT_UPDATE_SYSFS,
 };
 
+enum backlight_type {
+        BACKLIGHT_RAW = 1,
+        BACKLIGHT_PLATFORM,
+        BACKLIGHT_FIRMWARE,
+        BACKLIGHT_TYPE_MAX,
+};
+
 struct backlight_device;
 struct fb_info;
 
@@ -62,6 +69,8 @@ struct backlight_properties {
         /* FB Blanking active? (values as for power) */
         /* Due to be removed, please use (state & BL_CORE_FBBLANK) */
         int fb_blank;
+        /* Backlight type */
+        enum backlight_type type;
         /* Flags used to signal drivers of state changes */
         /* Upper 4 bits are reserved for driver internal use */
         unsigned int state;