Backlight - Carve out a better location for private driver functionality (#8329)

* rename backlight_soft to match rules.mk

* rename backlight_soft to match rules.mk - update common_features

* Carve out a better location for private driver backlight functionality

1 files changed, 48 insertions, 0 deletions

diff --git a/quantum/backlight/backlight_software.c b/quantum/backlight/backlight_software.c
new file mode 100644
index 000000000..709304f55
--- /dev/null
+++ b/quantum/backlight/backlight_software.c
@@ -0,0 +1,48 @@
+#include "quantum.h"
+#include "backlight.h"
+#include "backlight_driver_common.h"
+
+#ifdef BACKLIGHT_BREATHING
+#    error "Backlight breathing is not available for software PWM. Please disable."
+#endif
+
+static uint16_t s_duty_pattern = 0;
+
+// clang-format off
+
+/** \brief PWM duty patterns
+ *
+ * We scale the current backlight level to an index within this array. This allows
+ * backlight_task to focus on just switching LEDs on/off, and we can predict the duty pattern
+ */
+static const uint16_t backlight_duty_table[] = {
+    0b0000000000000000,
+    0b1000000000000000,
+    0b1000000010000000,
+    0b1000001000010000,
+    0b1000100010001000,
+    0b1001001001001000,
+    0b1010101010101010,
+    0b1110111011101110,
+    0b1111111111111111,
+};
+#define backlight_duty_table_size (sizeof(backlight_duty_table) / sizeof(backlight_duty_table[0]))
+
+// clang-format on
+
+static uint8_t scale_backlight(uint8_t v) { return v * (backlight_duty_table_size - 1) / BACKLIGHT_LEVELS; }
+
+void backlight_init_ports(void) { backlight_pins_init(); }
+
+void backlight_set(uint8_t level) { s_duty_pattern = backlight_duty_table[scale_backlight(level)]; }
+
+void backlight_task(void) {
+    static uint8_t backlight_tick = 0;
+
+    if (s_duty_pattern & ((uint16_t)1 << backlight_tick)) {
+        backlight_pins_on();
+    } else {
+        backlight_pins_off();
+    }
+    backlight_tick = (backlight_tick + 1) % 16;
+}