leds: pca955x: check for I2C errors

This should also allow probing to fail when a pca955x chip is not
found on a I2C bus.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

drivers/leds/leds-pca955x.c

@@ -165,13 +165,18 @@ static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
  * Write to frequency prescaler register, used to program the
  * period of the PWM output.  period = (PSCx + 1) / 38
  */
-static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
+	int ret;
 
-	i2c_smbus_write_byte_data(client,
+	ret = i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
 		val);
+	if (ret < 0)
+		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
+			__func__, n, val, ret);
+	return ret;
 }
 
 /*
@@ -181,38 +186,56 @@ static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
  *
  * Duty cycle is (256 - PWMx) / 256
  */
-static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
+	int ret;
 
-	i2c_smbus_write_byte_data(client,
+	ret = i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
 		val);
+	if (ret < 0)
+		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
+			__func__, n, val, ret);
+	return ret;
 }
 
 /*
  * Write to LED selector register, which determines the source that
  * drives the LED output.
  */
-static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
+	int ret;
 
-	i2c_smbus_write_byte_data(client,
+	ret = i2c_smbus_write_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
 		val);
+	if (ret < 0)
+		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
+			__func__, n, val, ret);
+	return ret;
 }
 
 /*
  * Read the LED selector register, which determines the source that
  * drives the LED output.
  */
-static u8 pca955x_read_ls(struct i2c_client *client, int n)
+static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
+	int ret;
 
-	return (u8) i2c_smbus_read_byte_data(client,
+	ret = i2c_smbus_read_byte_data(client,
 		pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
+	if (ret < 0) {
+		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
+			__func__, n, ret);
+		return ret;
+	}
+	*val = (u8)ret;
+	return 0;
 }
 
 static int pca955x_led_set(struct led_classdev *led_cdev,
@@ -223,6 +246,7 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 	u8 ls;
 	int chip_ls;	/* which LSx to use (0-3 potentially) */
 	int ls_led;	/* which set of bits within LSx to use (0-3) */
+	int ret;
 
 	pca955x_led = container_of(led_cdev, struct pca955x_led, led_cdev);
 	pca955x = pca955x_led->pca955x;
@@ -232,7 +256,9 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 
 	mutex_lock(&pca955x->lock);
 
-	ls = pca955x_read_ls(pca955x->client, chip_ls);
+	ret = pca955x_read_ls(pca955x->client, chip_ls, &ls);
+	if (ret)
+		goto out;
 
 	switch (value) {
 	case LED_FULL:
@@ -252,26 +278,37 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 		 * OFF, HALF, or FULL.  But, this is probably better than
 		 * just turning off for all other values.
 		 */
-		pca955x_write_pwm(pca955x->client, 1,
-				255 - value);
+		ret = pca955x_write_pwm(pca955x->client, 1, 255 - value);
+		if (ret)
+			goto out;
 		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
 		break;
 	}
 
-	pca955x_write_ls(pca955x->client, chip_ls, ls);
+	ret = pca955x_write_ls(pca955x->client, chip_ls, ls);
 
+out:
 	mutex_unlock(&pca955x->lock);
 
-	return 0;
+	return ret;
 }
 
 #ifdef CONFIG_LEDS_PCA955X_GPIO
 /*
  * Read the INPUT register, which contains the state of LEDs.
  */
-static u8 pca955x_read_input(struct i2c_client *client, int n)
+static int pca955x_read_input(struct i2c_client *client, int n, u8 *val)
 {
-	return (u8)i2c_smbus_read_byte_data(client, n);
+	int ret = i2c_smbus_read_byte_data(client, n);
+
+	if (ret < 0) {
+		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
+			__func__, n, ret);
+		return ret;
+	}
+	*val = (u8)ret;
+	return 0;
+
 }
 
 static int pca955x_gpio_request_pin(struct gpio_chip *gc, unsigned int offset)
@@ -285,23 +322,32 @@ static int pca955x_gpio_request_pin(struct gpio_chip *gc, unsigned int offset)
 	return -EBUSY;
 }
 
-static void pca955x_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
-				   int val)
+static int pca955x_set_value(struct gpio_chip *gc, unsigned int offset,
+			     int val)
 {
 	struct pca955x *pca955x = gpiochip_get_data(gc);
 	struct pca955x_led *led = &pca955x->leds[offset];
 
 	if (val)
-		pca955x_led_set(&led->led_cdev, LED_FULL);
+		return pca955x_led_set(&led->led_cdev, LED_FULL);
 	else
-		pca955x_led_set(&led->led_cdev, LED_OFF);
+		return pca955x_led_set(&led->led_cdev, LED_OFF);
+}
+
+static void pca955x_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
+				   int val)
+{
+	pca955x_set_value(gc, offset, val);
 }
 
 static int pca955x_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
 {
 	struct pca955x *pca955x = gpiochip_get_data(gc);
 	struct pca955x_led *led = &pca955x->leds[offset];
-	u8 reg = pca955x_read_input(pca955x->client, led->led_num / 8);
+	u8 reg = 0;
+
+	/* There is nothing we can do about errors */
+	pca955x_read_input(pca955x->client, led->led_num / 8, &reg);
 
 	return !!(reg & (1 << (led->led_num % 8)));
 }
@@ -310,17 +356,13 @@ static int pca955x_gpio_direction_input(struct gpio_chip *gc,
 					unsigned int offset)
 {
 	/* To use as input ensure pin is not driven */
-	pca955x_gpio_set_value(gc, offset, 0);
-
-	return 0;
+	return pca955x_set_value(gc, offset, 0);
 }
 
 static int pca955x_gpio_direction_output(struct gpio_chip *gc,
 					 unsigned int offset, int val)
 {
-	pca955x_gpio_set_value(gc, offset, val);
-
-	return 0;
+	return pca955x_set_value(gc, offset, val);
 }
 #endif /* CONFIG_LEDS_PCA955X_GPIO */
 
@@ -495,19 +537,29 @@ static int pca955x_probe(struct i2c_client *client,
 				return err;
 
 			/* Turn off LED */
-			pca955x_led_set(&pca955x_led->led_cdev, LED_OFF);
+			err = pca955x_led_set(&pca955x_led->led_cdev, LED_OFF);
+			if (err)
+				return err;
 		}
 	}
 
 	/* PWM0 is used for half brightness or 50% duty cycle */
-	pca955x_write_pwm(client, 0, 255-LED_HALF);
+	err = pca955x_write_pwm(client, 0, 255 - LED_HALF);
+	if (err)
+		return err;
 
 	/* PWM1 is used for variable brightness, default to OFF */
-	pca955x_write_pwm(client, 1, 0);
+	err = pca955x_write_pwm(client, 1, 0);
+	if (err)
+		return err;
 
 	/* Set to fast frequency so we do not see flashing */
-	pca955x_write_psc(client, 0, 0);
-	pca955x_write_psc(client, 1, 0);
+	err = pca955x_write_psc(client, 0, 0);
+	if (err)
+		return err;
+	err = pca955x_write_psc(client, 1, 0);
+	if (err)
+		return err;
 
 #ifdef CONFIG_LEDS_PCA955X_GPIO
 	if (ngpios) {