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SubjectRe: [PATCH] platform: fix samsung brightness min/max calculations
Date
From: Jason Stubbs <jasonbstubbs@gmail.com>

For one of the SABI configs, the valid brightness levels are 1 through 8 with
0 being reserved for the BIOS. To make the range 0-based, the driver is meant
to offset values to/from userspace by 1 giving valid levels of 0 through 7.

Currently, the driver is reporting a max brightness of 8 and doing the offset
the wrong way such that setting a brightness of 8 will set as 7 in hardware
while setting a brightness of 0 will attempt (and fail) to set as -1 in
hardware.

This patch fixes these calculations as well as a potential miscalculation due
to an assumption of min_brightness being either 0 or 1.

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 01d5278..995b041 100644
--- a/drivers/platform/x86/samsung-laptop.c
+++ b/drivers/platform/x86/samsung-laptop.c
@@ -370,15 +370,17 @@ static u8 read_brightness(void)
&sretval);
if (!retval) {
user_brightness = sretval.retval[0];
- if (user_brightness != 0)
+ if (user_brightness > sabi_config->min_brightness)
user_brightness -= sabi_config->min_brightness;
+ else
+ user_brightness = 0;
}
return user_brightness;
}

static void set_brightness(u8 user_brightness)
{
- u8 user_level = user_brightness - sabi_config->min_brightness;
+ u8 user_level = user_brightness + sabi_config->min_brightness;

if (user_level == read_brightness()) {
return;
@@ -799,7 +801,8 @@ 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;
+ props.max_brightness = sabi_config->max_brightness -
+ sabi_config->min_brightness;
backlight_device = backlight_device_register("samsung", &sdev->dev,
NULL, &backlight_ops,
&props);

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