gpiolib: translate pin number in GPIO ACPI callbacks

Hello qipeng.zha,

The patch 4de60970abf9: "gpiolib: translate pin number in GPIO ACPI callbacks" from Mar 11, 2015, leads to the following static checker warning:

drivers/gpio/gpiolib-acpi.c:559 acpi_gpio_adr_space_handler()
warn: unsigned 'pin' is never less than zero.

drivers/gpio/gpiolib-acpi.c
550
551 length = min(agpio->pin_table_length, (u16)(pin_index + bits));
552 for (i = pin_index; i < length; ++i) {

   553                  unsigned pin = agpio->pin_table[i];
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^

"pin" is already assigned.

   554                  struct acpi_gpio_connection *conn;
   555                  struct gpio_desc *desc;
   556                  bool found;
   557  
   558                  pin = acpi_gpiochip_pin_to_gpio_offset(chip, pin);
   559                  if (pin < 0) {
                            ^^^^^^^

Error checking doesn't work.

   560                          status = AE_BAD_PARAMETER;
   561                          goto out;
   562                  }
   563  
   564                  mutex_lock(&achip->conn_lock);

regards,
dan carpenter