Linux 内核设备驱动之GPIO驱动之GPIO gpiochip注册

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我是靠谱客的博主自由香菇，最近开发中收集的这篇文章主要介绍Linux 内核设备驱动之GPIO驱动之GPIO gpiochip注册，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述


/**
 * gpiochip_add_data() - register a gpio_chip
 * @chip: the chip to register, with chip->base initialized
 * Context: potentially before irqs will work
 *
 * Returns a negative errno if the chip can't be registered, such as
 * because the chip->base is invalid or already associated with a
 * different chip.  Otherwise it returns zero as a success code.
 *
 * When gpiochip_add_data() is called very early during boot, so that GPIOs
 * can be freely used, the chip->parent device must be registered before
 * the gpio framework's arch_initcall().  Otherwise sysfs initialization
 * for GPIOs will fail rudely.
 *
 * gpiochip_add_data() must only be called after gpiolib initialization,
 * ie after core_initcall().
 *
 * If chip->base is negative, this requests dynamic assignment of
 * a range of valid GPIOs.
 */
int gpiochip_add_data(struct gpio_chip *chip, void *data)
{
 unsigned long flags;
 int  status = 0;
 unsigned i;
 int  base = chip->base;
 struct gpio_device *gdev;
 /*
  * First: allocate and populate the internal stat container, and
  * set up the struct device.
  */
 gdev = kzalloc(sizeof(*gdev), GFP_KERNEL);
 if (!gdev)
  return -ENOMEM;
 gdev->dev.bus = &gpio_bus_type;
 gdev->chip = chip;
 chip->gpiodev = gdev;
 if (chip->parent) {
  gdev->dev.parent = chip->parent;
  gdev->dev.of_node = chip->parent->of_node;
 }
#ifdef CONFIG_OF_GPIO
 /* If the gpiochip has an assigned OF node this takes precedence */
 if (chip->of_node)
  gdev->dev.of_node = chip->of_node;
#endif
 gdev->id = ida_simple_get(&gpio_ida, 0, 0, GFP_KERNEL);
 if (gdev->id < 0) {
  status = gdev->id;
  goto err_free_gdev;
 }
 dev_set_name(&gdev->dev, "gpiochip%d", gdev->id);
 device_initialize(&gdev->dev);
 dev_set_drvdata(&gdev->dev, gdev);
 if (chip->parent && chip->parent->driver)
  gdev->owner = chip->parent->driver->owner;
 else if (chip->owner)
  /* TODO: remove chip->owner */
  gdev->owner = chip->owner;
 else
  gdev->owner = THIS_MODULE;
 gdev->descs = kcalloc(chip->ngpio, sizeof(gdev->descs[0]), GFP_KERNEL);
 if (!gdev->descs) {
  status = -ENOMEM;
  goto err_free_gdev;
 }
 if (chip->ngpio == 0) {
  chip_err(chip, "tried to insert a GPIO chip with zero linesn");
  status = -EINVAL;
  goto err_free_descs;
 }
 if (chip->label)
  gdev->label = kstrdup(chip->label, GFP_KERNEL);
 else
  gdev->label = kstrdup("unknown", GFP_KERNEL);
 if (!gdev->label) {
  status = -ENOMEM;
  goto err_free_descs;
 }
 gdev->ngpio = chip->ngpio;
 gdev->data = data;
 spin_lock_irqsave(&gpio_lock, flags);
 /*
  * TODO: this allocates a Linux GPIO number base in the global
  * GPIO numberspace for this chip. In the long run we want to
  * get *rid* of this numberspace and use only descriptors, but
  * it may be a pipe dream. It will not happen before we get rid
  * of the sysfs interface anyways.
  */
 if (base < 0) {
  base = gpiochip_find_base(chip->ngpio);
  if (base < 0) {
   status = base;
   spin_unlock_irqrestore(&gpio_lock, flags);
   goto err_free_label;
  }
  /*
   * TODO: it should not be necessary to reflect the assigned
   * base outside of the GPIO subsystem. Go over drivers and
   * see if anyone makes use of this, else drop this and assign
   * a poison instead.
   */
  chip->base = base;
 }
 gdev->base = base;
 status = gpiodev_add_to_list(gdev);
 if (status) {
  spin_unlock_irqrestore(&gpio_lock, flags);
  goto err_free_label;
 }
 spin_unlock_irqrestore(&gpio_lock, flags);
 for (i = 0; i < chip->ngpio; i++) {
  struct gpio_desc *desc = &gdev->descs[i];
  desc->gdev = gdev;
  /*
   * REVISIT: most hardware initializes GPIOs as inputs
   * (often with pullups enabled) so power usage is
   * minimized. Linux code should set the gpio direction
   * first thing; but until it does, and in case
   * chip->get_direction is not set, we may expose the
   * wrong direction in sysfs.
   */
  if (chip->get_direction) {
   /*
    * If we have .get_direction, set up the initial
    * direction flag from the hardware.
    */
   int dir = chip->get_direction(chip, i);
   if (!dir)
    set_bit(FLAG_IS_OUT, &desc->flags);
  } else if (!chip->direction_input) {
   /*
    * If the chip lacks the .direction_input callback
    * we logically assume all lines are outputs.
    */
   set_bit(FLAG_IS_OUT, &desc->flags);
  }
 }
#ifdef CONFIG_PINCTRL
 INIT_LIST_HEAD(&gdev->pin_ranges);
#endif
 status = gpiochip_set_desc_names(chip);
 if (status)
  goto err_remove_from_list;
 status = gpiochip_irqchip_init_valid_mask(chip);
 if (status)
  goto err_remove_from_list;
 status = of_gpiochip_add(chip);
 if (status)
  goto err_remove_chip;
 acpi_gpiochip_add(chip);
 /*
  * By first adding the chardev, and then adding the device,
  * we get a device node entry in sysfs under
  * /sys/bus/gpio/devices/gpiochipN/dev that can be used for
  * coldplug of device nodes and other udev business.
  * We can do this only if gpiolib has been initialized.
  * Otherwise, defer until later.
  */
 if (gpiolib_initialized) {
  status = gpiochip_setup_dev(gdev);
  if (status)
   goto err_remove_chip;
 }
 return 0;
err_remove_chip:
 acpi_gpiochip_remove(chip);
 gpiochip_free_hogs(chip);
 of_gpiochip_remove(chip);
 gpiochip_irqchip_free_valid_mask(chip);
err_remove_from_list:
 spin_lock_irqsave(&gpio_lock, flags);
 list_del(&gdev->list);
 spin_unlock_irqrestore(&gpio_lock, flags);
err_free_label:
 kfree(gdev->label);
err_free_descs:
 kfree(gdev->descs);
err_free_gdev:
 ida_simple_remove(&gpio_ida, gdev->id);
 /* failures here can mean systems won't boot... */
 pr_err("%s: GPIOs %d..%d (%s) failed to registern", __func__,
        gdev->base, gdev->base + gdev->ngpio - 1,
        chip->label ? : "generic");
 kfree(gdev);
 return status;
}