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Merge tag 'backlight-next-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight

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Pull backlight updates from Lee Jones:
 "New Functionality:
   - Provide support for ACPI enumeration; gpio_backlight

  Fix-ups:
   - SPDX fixups; pwm_bl
   - Fix linear	brightness levels to include number available; pwm_bl"

* tag 'backlight-next-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/backlight:
  backlight: pwm_bl: Fix heuristic to determine number of brightness levels
  backlight: gpio_backlight: Enable ACPI enumeration
  backlight: pwm_bl: Convert to use SPDX identifier
This commit is contained in:
Linus Torvalds
2019-07-16 09:25:04 -07:00
parent 9637d51734 73fbfc4994
commit 5095062641
2 changed files with 17 additions and 36 deletions
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30
drivers/video/backlight/pwm_bl.c
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@@ -1,8 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/drivers/video/backlight/pwm_bl.c
*
* simple PWM based backlight control, board code has to setup
* Simple PWM based backlight control, board code has to setup
* 1) pin configuration so PWM waveforms can output
* 2) platform_data being correctly configured
*/
@@ -191,29 +189,17 @@ int pwm_backlight_brightness_default(struct device *dev,
struct platform_pwm_backlight_data *data,
unsigned int period)
{
unsigned int counter = 0;
unsigned int i, n;
unsigned int i;
u64 retval;
/*
* Count the number of bits needed to represent the period number. The
* number of bits is used to calculate the number of levels used for the
* brightness-levels table, the purpose of this calculation is have a
* pre-computed table with enough levels to get linear brightness
* perception. The period is divided by the number of bits so for a
* 8-bit PWM we have 255 / 8 = 32 brightness levels or for a 16-bit PWM
* we have 65535 / 16 = 4096 brightness levels.
*
* Note that this method is based on empirical testing on different
* devices with PWM of 8 and 16 bits of resolution.
* Once we have 4096 levels there's little point going much higher...
* neither interactive sliders nor animation benefits from having
* more values in the table.
*/
n = period;
while (n) {
counter += n % 2;
n >>= 1;
}
data->max_brightness =
min((int)DIV_ROUND_UP(period, fls(period)), 4096);
data->max_brightness = DIV_ROUND_UP(period, counter);
data->levels = devm_kcalloc(dev, data->max_brightness,
sizeof(*data->levels), GFP_KERNEL);
if (!data->levels)
@@ -705,5 +691,5 @@ static struct platform_driver pwm_backlight_driver = {
module_platform_driver(pwm_backlight_driver);
MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:pwm-backlight");