+static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
+{
+ unsigned int nlevels = data->max_brightness + 1;
+ unsigned int min_val = data->levels[0];
+ unsigned int max_val = data->levels[nlevels - 1];
+ /*
+ * Multiplying by 128 means that even in pathological cases such
+ * as (max_val - min_val) == nlevels the error at max_val is less
+ * than 1%.
+ */
+ unsigned int slope = (128 * (max_val - min_val)) / nlevels;
+ unsigned int margin = (max_val - min_val) / 20; /* 5% */
+ int i;
+
+ for (i = 1; i < nlevels; i++) {
+ unsigned int linear_value = min_val + ((i * slope) / 128);
+ unsigned int delta = abs(linear_value - data->levels[i]);
+
+ if (delta > margin)
+ return false;
+ }
+
+ return true;
+}
+