Input: adp5588-keypad - fix NULL dereference in adp5588_gpio_add()

The kpad structure is assigned to i2c client via i2s_set_clientdata()
at the end of adp5588_probe(), but in adp5588_gpio_add() we tried to
access it (via dev_get_drvdata! which is not nice at all) causing an
oops.

Let's pass pointer to kpad directly into adp5588_gpio_add() and
adp5588_gpio_remove() to avoid accessing driver data before it is
set up.

Also split out building of gpiomap into a separate function to
clear the logic.
Reported-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/keyboard/adp5588-keys.c

@@ -173,16 +173,14 @@ static int adp5588_gpio_direction_output(struct gpio_chip *chip,
 	return ret;
 }
 
-static int __devinit adp5588_gpio_add(struct device *dev)
+static int __devinit adp5588_build_gpiomap(struct adp5588_kpad *kpad,
+				const struct adp5588_kpad_platform_data *pdata)
 {
-	struct adp5588_kpad *kpad = dev_get_drvdata(dev);
-	const struct adp5588_kpad_platform_data *pdata = dev->platform_data;
-	const struct adp5588_gpio_platform_data *gpio_data = pdata->gpio_data;
-	int i, error;
-
-	if (gpio_data) {
-		int j = 0;
 	bool pin_used[MAXGPIO];
+	int n_unused = 0;
+	int i;
+
+	memset(pin_used, 0, sizeof(pin_used));
 
 	for (i = 0; i < pdata->rows; i++)
 		pin_used[i] = true;
@@ -193,21 +191,31 @@ static int __devinit adp5588_gpio_add(struct device *dev)
 	for (i = 0; i < kpad->gpimapsize; i++)
 		pin_used[kpad->gpimap[i].pin - GPI_PIN_BASE] = true;
 
-		for (i = 0; i < MAXGPIO; i++) {
+	for (i = 0; i < MAXGPIO; i++)
 		if (!pin_used[i])
-				kpad->gpiomap[j++] = i;
-		}
-		kpad->gc.ngpio = j;
+			kpad->gpiomap[n_unused++] = i;
 
-		if (kpad->gc.ngpio)
-			kpad->export_gpio = true;
-	}
+	return n_unused;
+}
+
+static int __devinit adp5588_gpio_add(struct adp5588_kpad *kpad)
+{
+	struct device *dev = &kpad->client->dev;
+	const struct adp5588_kpad_platform_data *pdata = dev->platform_data;
+	const struct adp5588_gpio_platform_data *gpio_data = pdata->gpio_data;
+	int i, error;
 
-	if (!kpad->export_gpio) {
+	if (!gpio_data)
+		return 0;
+
+	kpad->gc.ngpio = adp5588_build_gpiomap(kpad, pdata);
+	if (kpad->gc.ngpio == 0) {
 		dev_info(dev, "No unused gpios left to export\n");
 		return 0;
 	}
 
+	kpad->export_gpio = true;
+
 	kpad->gc.direction_input = adp5588_gpio_direction_input;
 	kpad->gc.direction_output = adp5588_gpio_direction_output;
 	kpad->gc.get = adp5588_gpio_get_value;
@@ -243,9 +251,9 @@ static int __devinit adp5588_gpio_add(struct device *dev)
 	return 0;
 }
 
-static void __devexit adp5588_gpio_remove(struct device *dev)
+static void __devexit adp5588_gpio_remove(struct adp5588_kpad *kpad)
 {
-	struct adp5588_kpad *kpad = dev_get_drvdata(dev);
+	struct device *dev = &kpad->client->dev;
 	const struct adp5588_kpad_platform_data *pdata = dev->platform_data;
 	const struct adp5588_gpio_platform_data *gpio_data = pdata->gpio_data;
 	int error;
@@ -266,12 +274,12 @@ static void __devexit adp5588_gpio_remove(struct device *dev)
 		dev_warn(dev, "gpiochip_remove failed %d\n", error);
 }
 #else
-static inline int adp5588_gpio_add(struct device *dev)
+static inline int adp5588_gpio_add(struct adp5588_kpad *kpad)
 {
 	return 0;
 }
 
-static inline void adp5588_gpio_remove(struct device *dev)
+static inline void adp5588_gpio_remove(struct adp5588_kpad *kpad)
 {
 }
 #endif
@@ -581,7 +589,7 @@ static int __devinit adp5588_probe(struct i2c_client *client,
 	if (kpad->gpimapsize)
 		adp5588_report_switch_state(kpad);
 
-	error = adp5588_gpio_add(&client->dev);
+	error = adp5588_gpio_add(kpad);
 	if (error)
 		goto err_free_irq;
 
@@ -611,7 +619,7 @@ static int __devexit adp5588_remove(struct i2c_client *client)
 	free_irq(client->irq, kpad);
 	cancel_delayed_work_sync(&kpad->work);
 	input_unregister_device(kpad->input);
-	adp5588_gpio_remove(&client->dev);
+	adp5588_gpio_remove(kpad);
 	kfree(kpad);
 
 	return 0;