[PATCH] sony-laptop: limit brightness range to DSDT provided ones

The new style brightness control provides an operating range of 9 values
(seems consistent over a large number of models sharing the same
brightness control methods).
Read and use the minimum and maximum values to limit the backlight
interface between those boundaries.

Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

1 files changed, 103 insertions, 24 deletions

diff --git a/drivers/platform/x86/sony-laptop.c b/drivers/platform/x86/sony-laptop.c
index 9d80ae4e6be6..6fe8cd6e23b5 100644
--- a/drivers/platform/x86/sony-laptop.c
+++ b/drivers/platform/x86/sony-laptop.c
@@ -934,6 +934,14 @@ static ssize_t sony_nc_sysfs_store(struct device *dev,
 /*
  * Backlight device
  */
+struct sony_backlight_props {
+        struct backlight_device *dev;
+        int                     handle;
+        u8                      offset;
+        u8                      maxlvl;
+};
+struct sony_backlight_props sony_bl_props;
+
 static int sony_backlight_update_status(struct backlight_device *bd)
 {
         return acpi_callsetfunc(sony_nc_acpi_handle, "SBRT",
@@ -954,19 +962,23 @@ static int sony_nc_get_brightness_ng(struct backlight_device *bd)
 {
         int result;
         int *handle = (int *)bl_get_data(bd);
+        struct sony_backlight_props *sdev =
+                (struct sony_backlight_props *)bl_get_data(bd);
 
-        sony_call_snc_handle(*handle, 0x0200, &result);
+        sony_call_snc_handle(sdev->handle, 0x0200, &result);
 
-        return result & 0xff;
+        return (result & 0xff) - sdev->offset;
 }
 
 static int sony_nc_update_status_ng(struct backlight_device *bd)
 {
         int value, result;
         int *handle = (int *)bl_get_data(bd);
+        struct sony_backlight_props *sdev =
+                (struct sony_backlight_props *)bl_get_data(bd);
 
-        value = bd->props.brightness;
-        if (sony_call_snc_handle(*handle, 0x0100 | (value << 16), &result))
+        value = bd->props.brightness + sdev->offset;
+        if (sony_call_snc_handle(sdev->handle, 0x0100 | (value << 16), &result))
                 return -EIO;
 
         return value;
@@ -982,8 +994,6 @@ static const struct backlight_ops sony_backlight_ng_ops = {
         .update_status = sony_nc_update_status_ng,
         .get_brightness = sony_nc_get_brightness_ng,
 };
-static int backlight_ng_handle;
-static struct backlight_device *sony_backlight_device;
 
 /*
  * New SNC-only Vaios event mapping to driver known keys
@@ -1550,6 +1560,75 @@ static void sony_nc_kbd_backlight_resume(void)
                                 &ignore);
 }
 
+static void sony_nc_backlight_ng_read_limits(int handle,
+                struct sony_backlight_props *props)
+{
+        int offset;
+        acpi_status status;
+        u8 brlvl, i;
+        u8 min = 0xff, max = 0x00;
+        struct acpi_object_list params;
+        union acpi_object in_obj;
+        union acpi_object *lvl_enum;
+        struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+
+        props->handle = handle;
+        props->offset = 0;
+        props->maxlvl = 0xff;
+
+        offset = sony_find_snc_handle(handle);
+        if (offset < 0)
+                return;
+
+        /* try to read the boundaries from ACPI tables, if we fail the above
+         * defaults should be reasonable
+         */
+        params.count = 1;
+        params.pointer = &in_obj;
+        in_obj.type = ACPI_TYPE_INTEGER;
+        in_obj.integer.value = offset;
+        status = acpi_evaluate_object(sony_nc_acpi_handle, "SN06", &params,
+                        &buffer);
+        if (ACPI_FAILURE(status))
+                return;
+
+        lvl_enum = (union acpi_object *) buffer.pointer;
+        if (!lvl_enum) {
+                pr_err("No SN06 return object.");
+                return;
+        }
+        if (lvl_enum->type != ACPI_TYPE_BUFFER) {
+                pr_err("Invalid SN06 return object 0x%.2x\n",
+                       lvl_enum->type);
+                goto out_invalid;
+        }
+
+        /* the buffer lists brightness levels available, brightness levels are
+         * from 0 to 8 in the array, other values are used by ALS control.
+         */
+        for (i = 0; i < 9 && i < lvl_enum->buffer.length; i++) {
+
+                brlvl = *(lvl_enum->buffer.pointer + i);
+                dprintk("Brightness level: %d\n", brlvl);
+
+                if (!brlvl)
+                        break;
+
+                if (brlvl > max)
+                        max = brlvl;
+                if (brlvl < min)
+                        min = brlvl;
+        }
+        props->offset = min;
+        props->maxlvl = max;
+        dprintk("Brightness levels: min=%d max=%d\n", props->offset,
+                        props->maxlvl);
+
+out_invalid:
+        kfree(buffer.pointer);
+        return;
+}
+
 static void sony_nc_backlight_setup(void)
 {
         acpi_handle unused;
@@ -1558,14 +1637,14 @@ static void sony_nc_backlight_setup(void)
         struct backlight_properties props;
 
         if (sony_find_snc_handle(0x12f) != -1) {
-                backlight_ng_handle = 0x12f;
                 ops = &sony_backlight_ng_ops;
-                max_brightness = 0xff;
+                sony_nc_backlight_ng_read_limits(0x12f, &sony_bl_props);
+                max_brightness = sony_bl_props.maxlvl - sony_bl_props.offset;
 
         } else if (sony_find_snc_handle(0x137) != -1) {
-                backlight_ng_handle = 0x137;
                 ops = &sony_backlight_ng_ops;
-                max_brightness = 0xff;
+                sony_nc_backlight_ng_read_limits(0x137, &sony_bl_props);
+                max_brightness = sony_bl_props.maxlvl - sony_bl_props.offset;
 
         } else if (ACPI_SUCCESS(acpi_get_handle(sony_nc_acpi_handle, "GBRT",
                                                 &unused))) {
@@ -1578,22 +1657,22 @@ static void sony_nc_backlight_setup(void)
         memset(&props, 0, sizeof(struct backlight_properties));
         props.type = BACKLIGHT_PLATFORM;
         props.max_brightness = max_brightness;
-        sony_backlight_device = backlight_device_register("sony", NULL,
-                                                          &backlight_ng_handle,
-                                                          ops, &props);
+        sony_bl_props.dev = backlight_device_register("sony", NULL,
+                                                      &sony_bl_props,
+                                                      ops, &props);
 
-        if (IS_ERR(sony_backlight_device)) {
-                pr_warning(DRV_PFX "unable to register backlight device\n");
-                sony_backlight_device = NULL;
+        if (IS_ERR(sony_bl_props.dev)) {
+                pr_warn(DRV_PFX "unable to register backlight device\n");
+                sony_bl_props.dev = NULL;
         } else
-                sony_backlight_device->props.brightness =
-                    ops->get_brightness(sony_backlight_device);
+                sony_bl_props.dev->props.brightness =
+                        ops->get_brightness(sony_bl_props.dev);
 }
 
 static void sony_nc_backlight_cleanup(void)
 {
-        if (sony_backlight_device)
-                backlight_device_unregister(sony_backlight_device);
+        if (sony_bl_props.dev)
+                backlight_device_unregister(sony_bl_props.dev);
 }
 
 static int sony_nc_add(struct acpi_device *device)
@@ -2591,7 +2670,7 @@ static long sonypi_misc_ioctl(struct file *fp, unsigned int cmd,
         mutex_lock(&spic_dev.lock);
         switch (cmd) {
         case SONYPI_IOCGBRT:
-                if (sony_backlight_device == NULL) {
+                if (sony_bl_props.dev == NULL) {
                         ret = -EIO;
                         break;
                 }
@@ -2604,7 +2683,7 @@ static long sonypi_misc_ioctl(struct file *fp, unsigned int cmd,
                                 ret = -EFAULT;
                 break;
         case SONYPI_IOCSBRT:
-                if (sony_backlight_device == NULL) {
+                if (sony_bl_props.dev == NULL) {
                         ret = -EIO;
                         break;
                 }
@@ -2618,8 +2697,8 @@ static long sonypi_misc_ioctl(struct file *fp, unsigned int cmd,
                         break;
                 }
                 /* sync the backlight device status */
-                sony_backlight_device->props.brightness =
-                    sony_backlight_get_brightness(sony_backlight_device);
+                sony_bl_props.dev->props.brightness =
+                    sony_backlight_get_brightness(sony_bl_props.dev);
                 break;
         case SONYPI_IOCGBAT1CAP:
                 if (ec_read16(SONYPI_BAT1_FULL, &val16)) {