gpio: improve error path in gpiolib

At several places the gpiolib will proceed to handle a GPIO
descriptor even if it's ->chip member is NULL and no gpiochip
is associated.

Fix this by checking that both the descriptor cookie *and*
the chip pointer are valid.

Also bail out earlier with more specific diagnostic messages
on missing operations for setting as input/output or debounce.

ChangeLog v1->v2:
- Also return -EIO on gpiod_set_debounce() with missing
  operations in the vtable
- Fix indentations.

Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Frank Rowand <frank.rowand@sonymobile.com>
Cc: Tim Bird <tim.bird@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d6413b2..0cbddda 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1398,7 +1398,7 @@ static int gpiod_request(struct gpio_desc *desc, const char *label)
        int                     status = -EPROBE_DEFER;
        unsigned long           flags;
 
-       if (!desc) {
+       if (!desc || !desc->chip) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }
@@ -1406,8 +1406,6 @@ static int gpiod_request(struct gpio_desc *desc, const char *label)
        spin_lock_irqsave(&gpio_lock, flags);
 
        chip = desc->chip;
-       if (chip == NULL)
-               goto done;
 
        if (!try_module_get(chip->owner))
                goto done;
@@ -1630,16 +1628,20 @@ static int gpiod_direction_input(struct gpio_desc *desc)
        int                     status = -EINVAL;
        int                     offset;
 
-       if (!desc) {
+       if (!desc || !desc->chip) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }
 
+       chip = desc->chip;
+       if (!chip->get || !chip->direction_input) {
+               pr_warn("%s: missing get() or direction_input() operations\n",
+                       __func__);
+               return -EIO;
+       }
+
        spin_lock_irqsave(&gpio_lock, flags);
 
-       chip = desc->chip;
-       if (!chip || !chip->get || !chip->direction_input)
-               goto fail;
        status = gpio_ensure_requested(desc);
        if (status < 0)
                goto fail;
@@ -1691,7 +1693,7 @@ static int gpiod_direction_output(struct gpio_desc *desc, int value)
        int                     status = -EINVAL;
        int offset;
 
-       if (!desc) {
+       if (!desc || !desc->chip) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }
@@ -1704,11 +1706,15 @@ static int gpiod_direction_output(struct gpio_desc *desc, int value)
        if (!value && test_bit(FLAG_OPEN_SOURCE,  &desc->flags))
                return gpiod_direction_input(desc);
 
+       chip = desc->chip;
+       if (!chip->set || !chip->direction_output) {
+               pr_warn("%s: missing set() or direction_output() operations\n",
+                       __func__);
+               return -EIO;
+       }
+
        spin_lock_irqsave(&gpio_lock, flags);
 
-       chip = desc->chip;
-       if (!chip || !chip->set || !chip->direction_output)
-               goto fail;
        status = gpio_ensure_requested(desc);
        if (status < 0)
                goto fail;
@@ -1765,16 +1771,19 @@ static int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
        int                     status = -EINVAL;
        int                     offset;
 
-       if (!desc) {
+       if (!desc || !desc->chip) {
                pr_warn("%s: invalid GPIO\n", __func__);
                return -EINVAL;
        }
 
-       spin_lock_irqsave(&gpio_lock, flags);
-
        chip = desc->chip;
-       if (!chip || !chip->set || !chip->set_debounce)
-               goto fail;
+       if (!chip->set || !chip->set_debounce) {
+               pr_warn("%s: missing set() or set_debounce() operations\n",
+                       __func__);
+               return -EIO;
+       }
+
+       spin_lock_irqsave(&gpio_lock, flags);
 
        status = gpio_ensure_requested(desc);
        if (status < 0)