drivers/video/fbdev/core/fb_backlight.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 #include <linux/export.h>
   4 #include <linux/fb.h>
   5 #include <linux/mutex.h>
   6
   7 #if IS_ENABLED(CONFIG_FB_BACKLIGHT)
   8 /*
   9  * This function generates a linear backlight curve
  10  *
  11  *     0: off
  12  *   1-7: min
  13  * 8-127: linear from min to max
  14  */
  15 void fb_bl_default_curve(struct fb_info *fb_info, u8 off, u8 min, u8 max)
  16 {
  17         unsigned int i, flat, count, range = (max - min);
  18
  19         mutex_lock(&fb_info->bl_curve_mutex);
  20
  21         fb_info->bl_curve[0] = off;
  22
  23         for (flat = 1; flat < (FB_BACKLIGHT_LEVELS / 16); ++flat)
  24                 fb_info->bl_curve[flat] = min;
  25
  26         count = FB_BACKLIGHT_LEVELS * 15 / 16;
  27         for (i = 0; i < count; ++i)
  28                 fb_info->bl_curve[flat + i] = min + (range * (i + 1) / count);
  29
  30         mutex_unlock(&fb_info->bl_curve_mutex);
  31 }
  32 EXPORT_SYMBOL_GPL(fb_bl_default_curve);
  33
  34 struct backlight_device *fb_bl_device(struct fb_info *info)
  35 {
  36         return info->bl_dev;
  37 }
  38 EXPORT_SYMBOL(fb_bl_device);
  39 #endif