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Subject[PATCH] platform: add support for samsung nc210/nc110
Date
From: Jason Stubbs <jasonbstubbs@gmail.com>

This patch adds support for the NC210/NC110 to the samsung-laptop driver.

All SABI commands except for set_brightness work as expected. The behaviour
of set_brightness is as follows:

- Setting a new brightness will only step one level toward the new brightness
level. For example, setting a level of 5 when the current level is 2 will
result in a brightness level of 3.
- A spurious KEY_BRIGHTNESS_UP or KEY_BRIGHTNESS_DOWN event is also generated
along with the change in brightness.
- Neither of the above two issues occur when changing from/to brightness level 0.

Along with adding the DMI checks for the NC210/NC110, this patch adds
detection and a non-intrusive workaround for the above issues.

Signed-off-by: Jason Stubbs <jasonbstubbs@gmail.com>
--
diff --git a/drivers/platform/x86/samsung-laptop.c b/drivers/platform/x86/samsung-laptop.c
index ebf1b07..89fd703 100644
--- a/drivers/platform/x86/samsung-laptop.c
+++ b/drivers/platform/x86/samsung-laptop.c
@@ -226,6 +226,7 @@ static struct backlight_device *backlight_device;
static struct mutex sabi_mutex;
static struct platform_device *sdev;
static struct rfkill *rfk;
+static int has_stepping_quirk;

static int force;
module_param(force, bool, 0);
@@ -382,6 +383,17 @@ static void set_brightness(u8 user_brightness)
{
u8 user_level = user_brightness + sabi_config->min_brightness;

+ if (has_stepping_quirk && user_level != 0) {
+ /*
+ * short circuit if the specified level is what's already set
+ * to prevent the screen from flickering needlessly
+ */
+ if (user_brightness == read_brightness())
+ return;
+
+ sabi_set_command(sabi_config->commands.set_brightness, 0);
+ }
+
sabi_set_command(sabi_config->commands.set_brightness, user_level);
}

@@ -390,6 +402,34 @@ static int get_brightness(struct backlight_device *bd)
return (int)read_brightness();
}

+static void check_for_stepping_quirk(void)
+{
+ u8 initial_level = read_brightness();
+ u8 check_level;
+
+ /*
+ * Some laptops (nc210/nc110 at the very least) exhibit the strange
+ * behaviour of stepping toward rather than setting the brightness
+ * except when changing to/from brightness level 0. This behaviour
+ * is checked for here and worked around in set_brightness.
+ */
+
+ if (initial_level <= 2)
+ check_level = initial_level + 2;
+ else
+ check_level = initial_level - 2;
+
+ has_stepping_quirk = 0;
+ set_brightness(check_level);
+
+ if (read_brightness() != check_level) {
+ has_stepping_quirk = 1;
+ pr_info("enabled workaround for brightness stepping quirk\n");
+ }
+
+ set_brightness(initial_level);
+}
+
static int update_status(struct backlight_device *bd)
{
set_brightness(bd->props.brightness);
@@ -668,6 +708,15 @@ static struct dmi_system_id __initdata samsung_dmi_table[] = {
},
.callback = dmi_check_cb,
},
+ {
+ .ident = "NC210/NC110",
+ .matches = {
+ DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+ DMI_MATCH(DMI_PRODUCT_NAME, "NC210/NC110"),
+ DMI_MATCH(DMI_BOARD_NAME, "NC210/NC110"),
+ },
+ .callback = dmi_check_cb,
+ },
{ },
};
MODULE_DEVICE_TABLE(dmi, samsung_dmi_table);
@@ -776,6 +825,9 @@ static int __init samsung_init(void)
}
}

+ /* Check for stepping quirk */
+ check_for_stepping_quirk();
+
/* knock up a platform device to hang stuff off of */
sdev = platform_device_register_simple("samsung", -1, NULL, 0);
if (IS_ERR(sdev))

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