Add fan abstraction

src/board/system76/common/fan.c

@@ -8,3 +8,72 @@ void fan_reset(void) {
     // Do not manually set fans to maximum speed
     fan_max = false;
 }
+
+// Get duty cycle based on temperature, adapted from
+// https://github.com/pop-os/system76-power/blob/master/src/fan.rs
+uint8_t fan_duty(const struct Fan * fan, int16_t temp) __reentrant {
+    for (int i = 0; i < fan->points_size; i++) {
+        const struct FanPoint * cur = &fan->points[i];
+
+        // If exactly the current temp, return the current duty
+        if (temp == cur->temp) {
+            return cur->duty;
+        } else if (temp < cur->temp) {
+            // If lower than first temp, return 0%
+            if (i == 0) {
+                return PWM_DUTY(0);
+            } else {
+                const struct FanPoint * prev = &fan->points[i - 1];
+
+                if (fan->interpolate) {
+                    // If in between current temp and previous temp, interpolate
+                    if (temp > prev->temp) {
+                        int16_t dtemp = (cur->temp - prev->temp);
+                        int16_t dduty = ((int16_t)cur->duty) - ((int16_t)prev->duty);
+                        return (uint8_t)(
+                            ((int16_t)prev->duty) +
+                            ((temp - prev->temp) * dduty) / dtemp
+                        );
+                    }
+                } else {
+                    return prev->duty;
+                }
+            }
+        }
+    }
+
+    // If no point is found, return 100%
+    return PWM_DUTY(100);
+}
+
+uint8_t fan_heatup(const struct Fan * fan, uint8_t duty) __reentrant {
+    uint8_t lowest = duty;
+
+    int i;
+    for (i = 0; (i + 1) < fan->heatup_size; i++) {
+        uint8_t value = fan->heatup[i + 1];
+        if (value < lowest) {
+            lowest = value;
+        }
+        fan->heatup[i] = value;
+    }
+    fan->heatup[i] = duty;
+
+    return lowest;
+}
+
+uint8_t fan_cooldown(const struct Fan * fan, uint8_t duty) __reentrant {
+    uint8_t highest = duty;
+
+    int i;
+    for (i = 0; (i + 1) < fan->cooldown_size; i++) {
+        uint8_t value = fan->cooldown[i + 1];
+        if (value > highest) {
+            highest = value;
+        }
+        fan->cooldown[i] = value;
+    }
+    fan->cooldown[i] = duty;
+
+    return highest;
+}