GPIO fixes for the v4.7 cycle:

- It was discovered that too many parts of the kernel does not
   respect gpiod_to_irq() returning zero for an invalid IRQ.
   While this gets fixed, we need to make it return negative
   errorcodes again.
 
 - Harden the library a bit when passed error pointers. It is
   a bug to use these, but let's be helpful and warn the users.
 
 - Fix an uninitialized spinlock in the 104-idi-48 driver.
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Merge tag 'gpio-v4.7-4' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio

Pull GPIO fixes from Linus Walleij:
 "More GPIO fixes.  Most prominent the gpiod_to_irq() fix brought to my
  attention by Hans de Goede.  The hardening patch is a consequence of
  the reasoning around that bug.

   - It was discovered that too many parts of the kernel does not
     respect gpiod_to_irq() returning zero for an invalid IRQ.  While
     this gets fixed, we need to make it return negative errorcodes
     again.

   - Harden the library a bit when passed error pointers.  It is a bug
     to use these, but let's be helpful and warn the users.

   - Fix an uninitialized spinlock in the 104-idi-48 driver"

* tag 'gpio-v4.7-4' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio:
  gpio: make library immune to error pointers
  gpio: make sure gpiod_to_irq() returns negative on NULL desc
  gpio: 104-idi-48: Fix missing spin_lock_init for ack_lock

drivers/gpio/gpio-104-idi-48.c

@@ -247,6 +247,7 @@ static int idi_48_probe(struct device *dev, unsigned int id)
 	idi48gpio->irq = irq[id];
 
 	spin_lock_init(&idi48gpio->lock);
+	spin_lock_init(&idi48gpio->ack_lock);
 
 	dev_set_drvdata(dev, idi48gpio);
 

drivers/gpio/gpiolib.c

@@ -1373,8 +1373,12 @@ done:
 #define VALIDATE_DESC(desc) do { \
 	if (!desc) \
 		return 0; \
+	if (IS_ERR(desc)) {						\
+		pr_warn("%s: invalid GPIO (errorpointer)\n", __func__); \
+		return PTR_ERR(desc); \
+	} \
 	if (!desc->gdev) { \
-		pr_warn("%s: invalid GPIO\n", __func__); \
+		pr_warn("%s: invalid GPIO (no device)\n", __func__); \
 		return -EINVAL; \
 	} \
 	if ( !desc->gdev->chip ) { \
@@ -1386,8 +1390,12 @@ done:
 #define VALIDATE_DESC_VOID(desc) do { \
 	if (!desc) \
 		return; \
+	if (IS_ERR(desc)) {						\
+		pr_warn("%s: invalid GPIO (errorpointer)\n", __func__); \
+		return; \
+	} \
 	if (!desc->gdev) { \
-		pr_warn("%s: invalid GPIO\n", __func__); \
+		pr_warn("%s: invalid GPIO (no device)\n", __func__); \
 		return; \
 	} \
 	if (!desc->gdev->chip) { \
@@ -2056,7 +2064,14 @@ int gpiod_to_irq(const struct gpio_desc *desc)
 	struct gpio_chip *chip;
 	int offset;
 
-	VALIDATE_DESC(desc);
+	/*
+	 * Cannot VALIDATE_DESC() here as gpiod_to_irq() consumer semantics
+	 * requires this function to not return zero on an invalid descriptor
+	 * but rather a negative error number.
+	 */
+	if (!desc || IS_ERR(desc) || !desc->gdev || !desc->gdev->chip)
+		return -EINVAL;
+
 	chip = desc->gdev->chip;
 	offset = gpio_chip_hwgpio(desc);
 	if (chip->to_irq) {