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/** * Convert a GPIO number to its descriptor */struct gpio_desc *gpio_to_desc(unsigned gpio){ struct gpio_device *gdev; unsigned long flags;  spin_lock_irqsave(&gpio_lock, flags);  list_for_each_entry(gdev, &gpio_devices, list) {  if (gdev->base <= gpio &&      gdev->base + gdev->ngpio > gpio) {   spin_unlock_irqrestore(&gpio_lock, flags);   return &gdev->descs[gpio - gdev->base];  } }  spin_unlock_irqrestore(&gpio_lock, flags);  if (!gpio_is_valid(gpio))  WARN(1, "invalid GPIO %d\n", gpio);  return NULL;}EXPORT_SYMBOL_GPL(gpio_to_desc);

/** * Get the GPIO descriptor corresponding to the given hw number for this chip. */struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip,        u16 hwnum){ struct gpio_device *gdev = chip->gpiodev;  if (hwnum >= gdev->ngpio)  return ERR_PTR(-EINVAL);  return &gdev->descs[hwnum];}

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