arch/powerpc/platforms/powermac/backlight.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Miscellaneous procedures for dealing with the PowerMac hardware.
   4  * Contains support for the backlight.
   5  *
   6  *   Copyright (C) 2000 Benjamin Herrenschmidt
   7  *   Copyright (C) 2006 Michael Hanselmann <[email protected]>
   8  *
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/backlight.h>
  13 #include <linux/adb.h>
  14 #include <linux/pmu.h>
  15 #include <linux/atomic.h>
  16 #include <linux/export.h>
  17 #include <asm/backlight.h>
  18
  19 #define OLD_BACKLIGHT_MAX 15
  20
  21 static void pmac_backlight_key_worker(struct work_struct *work);
  22 static void pmac_backlight_set_legacy_worker(struct work_struct *work);
  23
  24 static DECLARE_WORK(pmac_backlight_key_work, pmac_backlight_key_worker);
  25 static DECLARE_WORK(pmac_backlight_set_legacy_work, pmac_backlight_set_legacy_worker);
  26
  27 /* Although these variables are used in interrupt context, it makes no sense to
  28  * protect them. No user is able to produce enough key events per second and
  29  * notice the errors that might happen.
  30  */
  31 static int pmac_backlight_key_queued;
  32 static int pmac_backlight_set_legacy_queued;
  33
  34 /* The via-pmu code allows the backlight to be grabbed, in which case the
  35  * in-kernel control of the brightness needs to be disabled. This should
  36  * only be used by really old PowerBooks.
  37  */
  38 static atomic_t kernel_backlight_disabled = ATOMIC_INIT(0);
  39
  40 /* Protect the pmac_backlight variable below.
  41    You should hold this lock when using the pmac_backlight pointer to
  42    prevent its potential removal. */
  43 DEFINE_MUTEX(pmac_backlight_mutex);
  44
  45 /* Main backlight storage
  46  *
  47  * Backlight drivers in this variable are required to have the "ops"
  48  * attribute set and to have an update_status function.
  49  *
  50  * We can only store one backlight here, but since Apple laptops have only one
  51  * internal display, it doesn't matter. Other backlight drivers can be used
  52  * independently.
  53  *
  54  */
  55 struct backlight_device *pmac_backlight;
  56
  57 int pmac_has_backlight_type(const char *type)
  58 {
  59         struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
  60
  61         if (bk_node) {
  62                 const char *prop = of_get_property(bk_node,
  63                                 "backlight-control", NULL);
  64                 if (prop && strncmp(prop, type, strlen(type)) == 0) {
  65                         of_node_put(bk_node);
  66                         return 1;
  67                 }
  68                 of_node_put(bk_node);
  69         }
  70
  71         return 0;
  72 }
  73
  74 static void pmac_backlight_key_worker(struct work_struct *work)
  75 {
  76         if (atomic_read(&kernel_backlight_disabled))
  77                 return;
  78
  79         mutex_lock(&pmac_backlight_mutex);
  80         if (pmac_backlight) {
  81                 struct backlight_properties *props;
  82                 int brightness;
  83
  84                 props = &pmac_backlight->props;
  85
  86                 brightness = props->brightness +
  87                         ((pmac_backlight_key_queued?-1:1) *
  88                          (props->max_brightness / 15));
  89
  90                 if (brightness < 0)
  91                         brightness = 0;
  92                 else if (brightness > props->max_brightness)
  93                         brightness = props->max_brightness;
  94
  95                 props->brightness = brightness;
  96                 backlight_update_status(pmac_backlight);
  97         }
  98         mutex_unlock(&pmac_backlight_mutex);
  99 }
 100
 101 /* This function is called in interrupt context */
 102 void pmac_backlight_key(int direction)
 103 {
 104         if (atomic_read(&kernel_backlight_disabled))
 105                 return;
 106
 107         /* we can receive multiple interrupts here, but the scheduled work
 108          * will run only once, with the last value
 109          */
 110         pmac_backlight_key_queued = direction;
 111         schedule_work(&pmac_backlight_key_work);
 112 }
 113
 114 static int __pmac_backlight_set_legacy_brightness(int brightness)
 115 {
 116         int error = -ENXIO;
 117
 118         mutex_lock(&pmac_backlight_mutex);
 119         if (pmac_backlight) {
 120                 struct backlight_properties *props;
 121
 122                 props = &pmac_backlight->props;
 123                 props->brightness = brightness *
 124                         (props->max_brightness + 1) /
 125                         (OLD_BACKLIGHT_MAX + 1);
 126
 127                 if (props->brightness > props->max_brightness)
 128                         props->brightness = props->max_brightness;
 129                 else if (props->brightness < 0)
 130                         props->brightness = 0;
 131
 132                 backlight_update_status(pmac_backlight);
 133
 134                 error = 0;
 135         }
 136         mutex_unlock(&pmac_backlight_mutex);
 137
 138         return error;
 139 }
 140
 141 static void pmac_backlight_set_legacy_worker(struct work_struct *work)
 142 {
 143         if (atomic_read(&kernel_backlight_disabled))
 144                 return;
 145
 146         __pmac_backlight_set_legacy_brightness(pmac_backlight_set_legacy_queued);
 147 }
 148
 149 /* This function is called in interrupt context */
 150 void pmac_backlight_set_legacy_brightness_pmu(int brightness) {
 151         if (atomic_read(&kernel_backlight_disabled))
 152                 return;
 153
 154         pmac_backlight_set_legacy_queued = brightness;
 155         schedule_work(&pmac_backlight_set_legacy_work);
 156 }
 157
 158 int pmac_backlight_set_legacy_brightness(int brightness)
 159 {
 160         return __pmac_backlight_set_legacy_brightness(brightness);
 161 }
 162
 163 int pmac_backlight_get_legacy_brightness(void)
 164 {
 165         int result = -ENXIO;
 166
 167         mutex_lock(&pmac_backlight_mutex);
 168         if (pmac_backlight) {
 169                 struct backlight_properties *props;
 170
 171                 props = &pmac_backlight->props;
 172
 173                 result = props->brightness *
 174                         (OLD_BACKLIGHT_MAX + 1) /
 175                         (props->max_brightness + 1);
 176         }
 177         mutex_unlock(&pmac_backlight_mutex);
 178
 179         return result;
 180 }
 181
 182 void pmac_backlight_disable(void)
 183 {
 184         atomic_inc(&kernel_backlight_disabled);
 185 }
 186
 187 void pmac_backlight_enable(void)
 188 {
 189         atomic_dec(&kernel_backlight_disabled);
 190 }
 191
 192 EXPORT_SYMBOL_GPL(pmac_backlight);
 193 EXPORT_SYMBOL_GPL(pmac_backlight_mutex);
 194 EXPORT_SYMBOL_GPL(pmac_has_backlight_type);