pwm-backlight: Track enable state

Follow up patches will add support for more complex means of powering
the backlight on and off such as using a regulator. To prevent calls to
the regulator API from becoming unbalanced, keep track of the enabled
state internally.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index ab9d5e6..4053efb 100644 (file)
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -27,6 +27,7 @@ struct pwm_bl_data {
        unsigned int            period;
        unsigned int            lth_brightness;
        unsigned int            *levels;
+       bool                    enabled;
        int                     (*notify)(struct device *,
                                          int brightness);
        void                    (*notify_after)(struct device *,
@@ -40,6 +41,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
 {
        int duty_cycle, err;
 
+       if (pb->enabled)
+               return;
+
        if (pb->levels) {
                duty_cycle = pb->levels[brightness];
                max = pb->levels[max];
@@ -52,12 +56,18 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness,
 
        pwm_config(pb->pwm, duty_cycle, pb->period);
        pwm_enable(pb->pwm);
+       pb->enabled = true;
 }
 
 static void pwm_backlight_power_off(struct pwm_bl_data *pb)
 {
+       if (!pb->enabled)
+               return;
+
        pwm_config(pb->pwm, 0, pb->period);
        pwm_disable(pb->pwm);
+
+       pb->enabled = false;
 }
 
 static int pwm_backlight_update_status(struct backlight_device *bl)
@@ -216,6 +226,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
        pb->check_fb = data->check_fb;
        pb->exit = data->exit;
        pb->dev = &pdev->dev;
+       pb->enabled = false;
 
        pb->pwm = devm_pwm_get(&pdev->dev, NULL);
        if (IS_ERR(pb->pwm)) {