ACPI: ibm_acpi: Add support for the generic backlight device

Add support for the generic backlight interface below /sys/class/backlight.
The patch keeps the procfs brightness handling for backward compatibility.

Add two generic functions brightness_get and brightness_set
to be used both by the procfs related and the sysfs related methods.

[apw@shadowen.org: backlight users need to select BACKLIGHT_CLASS_DEVICE]

Signed-off-by: Holger Macht <hmacht@suse.de>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 62 insertions, 14 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 0f9d4be7ed75..bc58a3b18e06 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -200,6 +200,7 @@ config ACPI_ASUS
 config ACPI_IBM
         tristate "IBM ThinkPad Laptop Extras"
         depends on X86
+        select BACKLIGHT_CLASS_DEVICE
         ---help---
           This is a Linux ACPI driver for the IBM ThinkPad laptops. It adds
           support for Fn-Fx key combinations, Bluetooth control, video
diff --git a/drivers/acpi/ibm_acpi.c b/drivers/acpi/ibm_acpi.c
index 003a9876c968..cd8722e4157e 100644
--- a/drivers/acpi/ibm_acpi.c
+++ b/drivers/acpi/ibm_acpi.c
@@ -78,6 +78,7 @@
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/proc_fs.h>
+#include <linux/backlight.h>
 #include <asm/uaccess.h>
 
 #include <acpi/acpi_drivers.h>
@@ -243,6 +244,8 @@ struct ibm_struct {
 
 static struct proc_dir_entry *proc_dir = NULL;
 
+static struct backlight_device *ibm_backlight_device;
+
 #define onoff(status,bit) ((status) & (1 << (bit)) ? "on" : "off")
 #define enabled(status,bit) ((status) & (1 << (bit)) ? "enabled" : "disabled")
 #define strlencmp(a,b) (strncmp((a), (b), strlen(b)))
@@ -1381,12 +1384,22 @@ static int ecdump_write(char *buf)
 
 static int brightness_offset = 0x31;
 
+static int brightness_get(struct backlight_device *bd)
+{
+       u8 level;
+       if (!acpi_ec_read(brightness_offset, &level))
+               return -EIO;
+
+       level &= 0x7;
+       return level;
+}
+
 static int brightness_read(char *p)
 {
         int len = 0;
-        u8 level;
+        int level;
 
-        if (!acpi_ec_read(brightness_offset, &level)) {
+        if ((level = brightness_get(NULL)) < 0) {
                 len += sprintf(p + len, "level:\t\tunreadable\n");
         } else {
                 len += sprintf(p + len, "level:\t\t%d\n", level & 0x7);
@@ -1401,16 +1414,34 @@ static int brightness_read(char *p)
 #define BRIGHTNESS_UP   4
 #define BRIGHTNESS_DOWN 5
 
-static int brightness_write(char *buf)
+static int brightness_set(int value)
 {
         int cmos_cmd, inc, i;
-        u8 level;
+        int current_value = brightness_get(NULL);
+
+        value &= 7;
+
+        cmos_cmd = value > current_value ? BRIGHTNESS_UP : BRIGHTNESS_DOWN;
+        inc = value > current_value ? 1 : -1;
+        for (i = current_value; i != value; i += inc) {
+                if (!cmos_eval(cmos_cmd))
+                        return -EIO;
+                if (!acpi_ec_write(brightness_offset, i + inc))
+                        return -EIO;
+        }
+
+        return 0;
+}
+
+static int brightness_write(char *buf)
+{
+        int level;
         int new_level;
         char *cmd;
 
         while ((cmd = next_cmd(&buf))) {
-                if (!acpi_ec_read(brightness_offset, &level))
-                        return -EIO;
+                if ((level = brightness_get(NULL)) < 0)
+                        return level;
                 level &= 7;
 
                 if (strlencmp(cmd, "up") == 0) {
@@ -1423,19 +1454,17 @@ static int brightness_write(char *buf)
                 } else
                         return -EINVAL;
 
-                cmos_cmd = new_level > level ? BRIGHTNESS_UP : BRIGHTNESS_DOWN;
-                inc = new_level > level ? 1 : -1;
-                for (i = level; i != new_level; i += inc) {
-                        if (!cmos_eval(cmos_cmd))
-                                return -EIO;
-                        if (!acpi_ec_write(brightness_offset, i + inc))
-                                return -EIO;
-                }
+                brightness_set(new_level);
         }
 
         return 0;
 }
 
+static int brightness_update_status(struct backlight_device *bd)
+{
+        return brightness_set(bd->props->brightness);
+}
+
 static int volume_offset = 0x30;
 
 static int volume_read(char *p)
@@ -1963,10 +1992,20 @@ IBM_PARAM(brightness);
 IBM_PARAM(volume);
 IBM_PARAM(fan);
 
+static struct backlight_properties ibm_backlight_data = {
+        .owner          = THIS_MODULE,
+        .get_brightness = brightness_get,
+        .update_status  = brightness_update_status,
+        .max_brightness = 7,
+};
+
 static void acpi_ibm_exit(void)
 {
         int i;
 
+        if (ibm_backlight_device)
+                backlight_device_unregister(ibm_backlight_device);
+
         for (i = ARRAY_SIZE(ibms) - 1; i >= 0; i--)
                 ibm_exit(&ibms[i]);
 
@@ -2034,6 +2073,14 @@ static int __init acpi_ibm_init(void)
                 }
         }
 
+        ibm_backlight_device = backlight_device_register("ibm", NULL,
+                                                         &ibm_backlight_data);
+        if (IS_ERR(ibm_backlight_device)) {
+                printk(IBM_ERR "Could not register ibm backlight device\n");
+                ibm_backlight_device = NULL;
+                acpi_ibm_exit();
+        }
+
         return 0;
 }