gpio: make the gpiochip a real device
GPIO chips have been around for years, but were never real devices,
instead they were piggy-backing on a parent device (such as a
platform_device or amba_device) but this was always optional.
GPIO chips could also exist without any device at all, with its
struct device *parent (ex *dev) pointer being set to null.
When sysfs was in use, a mock device would be created, with the
optional parent assigned, or just floating orphaned with NULL
as parent.
If sysfs is active, it will use this device as parent.
We now create a gpio_device struct containing a real
struct device and move the subsystem over to using that. The
list of struct gpio_chip:s is augmented to hold struct
gpio_device:s and we find gpio_chips:s by first looking up
the struct gpio_device.
The struct gpio_device is designed to stay around even if the
gpio_chip is removed, so as to satisfy users in userspace
that need a backing data structure to hold the state of the
session initiated with e.g. a character device even if there is
no physical chip anymore.
From this point on, gpiochips are devices.
Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 405dfca..28d3bf2 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -547,6 +547,7 @@
int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
{
struct gpio_chip *chip;
+ struct gpio_device *gdev;
struct gpiod_data *data;
unsigned long flags;
int status;
@@ -566,6 +567,7 @@
}
chip = desc->chip;
+ gdev = chip->gpiodev;
mutex_lock(&sysfs_lock);
@@ -605,7 +607,7 @@
if (chip->names && chip->names[offset])
ioname = chip->names[offset];
- dev = device_create_with_groups(&gpio_class, chip->parent,
+ dev = device_create_with_groups(&gpio_class, &gdev->dev,
MKDEV(0, 0), data, gpio_groups,
ioname ? ioname : "gpio%u",
desc_to_gpio(desc));
@@ -771,7 +773,7 @@
{
int status;
unsigned long flags;
- struct gpio_chip *chip;
+ struct gpio_device *gdev;
status = class_register(&gpio_class);
if (status < 0)
@@ -784,8 +786,8 @@
* registered, and so arch_initcall() can always gpio_export().
*/
spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(chip, &gpio_chips, list) {
- if (chip->cdev)
+ list_for_each_entry(gdev, &gpio_devices, list) {
+ if (gdev->chip->cdev)
continue;
/*
@@ -798,7 +800,7 @@
* gpio_lock prevents us from doing this.
*/
spin_unlock_irqrestore(&gpio_lock, flags);
- status = gpiochip_sysfs_register(chip);
+ status = gpiochip_sysfs_register(gdev->chip);
spin_lock_irqsave(&gpio_lock, flags);
}
spin_unlock_irqrestore(&gpio_lock, flags);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5c1ba87..3a073ab 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -16,6 +16,7 @@
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/pinctrl/consumer.h>
+#include <linux/idr.h>
#include "gpiolib.h"
@@ -42,6 +43,9 @@
#define extra_checks 0
#endif
+/* Device and char device-related information */
+static DEFINE_IDA(gpio_ida);
+
/* gpio_lock prevents conflicts during gpio_desc[] table updates.
* While any GPIO is requested, its gpio_chip is not removable;
* each GPIO's "requested" flag serves as a lock and refcount.
@@ -50,8 +54,7 @@
static DEFINE_MUTEX(gpio_lookup_lock);
static LIST_HEAD(gpio_lookup_list);
-LIST_HEAD(gpio_chips);
-
+LIST_HEAD(gpio_devices);
static void gpiochip_free_hogs(struct gpio_chip *chip);
static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
@@ -67,15 +70,16 @@
*/
struct gpio_desc *gpio_to_desc(unsigned gpio)
{
- struct gpio_chip *chip;
+ struct gpio_device *gdev;
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(chip, &gpio_chips, list) {
- if (chip->base <= gpio && chip->base + chip->ngpio > gpio) {
+ list_for_each_entry(gdev, &gpio_devices, list) {
+ if (gdev->chip->base <= gpio &&
+ gdev->chip->base + gdev->chip->ngpio > gpio) {
spin_unlock_irqrestore(&gpio_lock, flags);
- return &chip->desc[gpio - chip->base];
+ return &gdev->chip->desc[gpio - gdev->chip->base];
}
}
@@ -125,16 +129,16 @@
/* dynamic allocation of GPIOs, e.g. on a hotplugged device */
static int gpiochip_find_base(int ngpio)
{
- struct gpio_chip *chip;
+ struct gpio_device *gdev;
int base = ARCH_NR_GPIOS - ngpio;
- list_for_each_entry_reverse(chip, &gpio_chips, list) {
+ list_for_each_entry_reverse(gdev, &gpio_devices, list) {
/* found a free space? */
- if (chip->base + chip->ngpio <= base)
+ if (gdev->chip->base + gdev->chip->ngpio <= base)
break;
else
/* nope, check the space right before the chip */
- base = chip->base - ngpio;
+ base = gdev->chip->base - ngpio;
}
if (gpio_is_valid(base)) {
@@ -187,18 +191,28 @@
* Return -EBUSY if the new chip overlaps with some other chip's integer
* space.
*/
-static int gpiochip_add_to_list(struct gpio_chip *chip)
+static int gpiodev_add_to_list(struct gpio_device *gdev)
{
- struct gpio_chip *iterator;
- struct gpio_chip *previous = NULL;
+ struct gpio_device *iterator;
+ struct gpio_device *previous = NULL;
- if (list_empty(&gpio_chips)) {
- list_add_tail(&chip->list, &gpio_chips);
+ if (!gdev->chip)
+ return -EINVAL;
+
+ if (list_empty(&gpio_devices)) {
+ list_add_tail(&gdev->list, &gpio_devices);
return 0;
}
- list_for_each_entry(iterator, &gpio_chips, list) {
- if (iterator->base >= chip->base + chip->ngpio) {
+ list_for_each_entry(iterator, &gpio_devices, list) {
+ /*
+ * The list may contain dangling GPIO devices with no
+ * live chip assigned.
+ */
+ if (!iterator->chip)
+ continue;
+ if (iterator->chip->base >=
+ gdev->chip->base + gdev->chip->ngpio) {
/*
* Iterator is the first GPIO chip so there is no
* previous one
@@ -211,8 +225,8 @@
* [base, base + ngpio - 1]) between previous
* and iterator chip.
*/
- if (previous->base + previous->ngpio
- <= chip->base)
+ if (previous->chip->base + previous->chip->ngpio
+ <= gdev->chip->base)
goto found;
}
}
@@ -225,18 +239,18 @@
* Let iterator point to the last chip in the list.
*/
- iterator = list_last_entry(&gpio_chips, struct gpio_chip, list);
- if (iterator->base + iterator->ngpio <= chip->base) {
- list_add(&chip->list, &iterator->list);
+ iterator = list_last_entry(&gpio_devices, struct gpio_device, list);
+ if (iterator->chip->base + iterator->chip->ngpio <= gdev->chip->base) {
+ list_add(&gdev->list, &iterator->list);
return 0;
}
- dev_err(chip->parent,
+ dev_err(&gdev->dev,
"GPIO integer space overlap, cannot add chip\n");
return -EBUSY;
found:
- list_add_tail(&chip->list, &iterator->list);
+ list_add_tail(&gdev->list, &iterator->list);
return 0;
}
@@ -245,16 +259,16 @@
*/
static struct gpio_desc *gpio_name_to_desc(const char * const name)
{
- struct gpio_chip *chip;
+ struct gpio_device *gdev;
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(chip, &gpio_chips, list) {
+ list_for_each_entry(gdev, &gpio_devices, list) {
int i;
- for (i = 0; i != chip->ngpio; ++i) {
- struct gpio_desc *gpio = &chip->desc[i];
+ for (i = 0; i != gdev->chip->ngpio; ++i) {
+ struct gpio_desc *gpio = &gdev->chip->desc[i];
if (!gpio->name || !name)
continue;
@@ -302,6 +316,14 @@
return 0;
}
+static void gpiodevice_release(struct device *dev)
+{
+ struct gpio_device *gdev = dev_get_drvdata(dev);
+
+ list_del(&gdev->list);
+ ida_simple_remove(&gpio_ida, gdev->id);
+}
+
/**
* gpiochip_add_data() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
@@ -323,19 +345,60 @@
{
unsigned long flags;
int status = 0;
- unsigned id;
+ unsigned i;
int base = chip->base;
struct gpio_desc *descs;
+ struct gpio_device *gdev;
- descs = kcalloc(chip->ngpio, sizeof(descs[0]), GFP_KERNEL);
- if (!descs)
+ /*
+ * First: allocate and populate the internal stat container, and
+ * set up the struct device.
+ */
+ gdev = kmalloc(sizeof(*gdev), GFP_KERNEL);
+ if (!gdev)
return -ENOMEM;
+ gdev->chip = chip;
+ chip->gpiodev = gdev;
+ if (chip->parent) {
+ gdev->dev.parent = chip->parent;
+ gdev->dev.of_node = chip->parent->of_node;
+ } else {
+#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;
+ /* FIXME: devm_kcalloc() these and move to gpio_device */
+ descs = kcalloc(chip->ngpio, sizeof(descs[0]), GFP_KERNEL);
+ if (!descs) {
+ status = -ENOMEM;
+ goto err_free_gdev;
+ }
+
+ /* FIXME: move driver data into gpio_device dev_set_drvdata() */
chip->data = data;
if (chip->ngpio == 0) {
chip_err(chip, "tried to insert a GPIO chip with zero lines\n");
- return -EINVAL;
+ status = -EINVAL;
+ goto err_free_descs;
}
spin_lock_irqsave(&gpio_lock, flags);
@@ -350,15 +413,16 @@
chip->base = base;
}
- status = gpiochip_add_to_list(chip);
+ status = gpiodev_add_to_list(gdev);
if (status) {
spin_unlock_irqrestore(&gpio_lock, flags);
goto err_free_descs;
}
- for (id = 0; id < chip->ngpio; id++) {
- struct gpio_desc *desc = &descs[id];
+ for (i = 0; i < chip->ngpio; i++) {
+ struct gpio_desc *desc = &descs[i];
+ /* REVISIT: maybe a pointer to gpio_device is better */
desc->chip = chip;
/* REVISIT: most hardware initializes GPIOs as inputs (often
@@ -369,18 +433,15 @@
*/
desc->flags = !chip->direction_input ? (1 << FLAG_IS_OUT) : 0;
}
-
chip->desc = descs;
spin_unlock_irqrestore(&gpio_lock, flags);
#ifdef CONFIG_PINCTRL
+ /* FIXME: move pin ranges to gpio_device */
INIT_LIST_HEAD(&chip->pin_ranges);
#endif
- if (!chip->owner && chip->parent && chip->parent->driver)
- chip->owner = chip->parent->driver->owner;
-
status = gpiochip_set_desc_names(chip);
if (status)
goto err_remove_from_list;
@@ -391,28 +452,39 @@
acpi_gpiochip_add(chip);
- status = gpiochip_sysfs_register(chip);
+ status = device_add(&gdev->dev);
if (status)
goto err_remove_chip;
+ status = gpiochip_sysfs_register(chip);
+ if (status)
+ goto err_remove_device;
+
+ /* From this point, the .release() function cleans up gpio_device */
+ gdev->dev.release = gpiodevice_release;
+ get_device(&gdev->dev);
pr_debug("%s: registered GPIOs %d to %d on device: %s\n", __func__,
chip->base, chip->base + chip->ngpio - 1,
chip->label ? : "generic");
return 0;
+err_remove_device:
+ device_del(&gdev->dev);
err_remove_chip:
acpi_gpiochip_remove(chip);
gpiochip_free_hogs(chip);
of_gpiochip_remove(chip);
err_remove_from_list:
spin_lock_irqsave(&gpio_lock, flags);
- list_del(&chip->list);
+ list_del(&gdev->list);
spin_unlock_irqrestore(&gpio_lock, flags);
chip->desc = NULL;
err_free_descs:
kfree(descs);
-
+err_free_gdev:
+ ida_simple_remove(&gpio_ida, gdev->id);
+ kfree(gdev);
/* failures here can mean systems won't boot... */
pr_err("%s: GPIOs %d..%d (%s) failed to register\n", __func__,
chip->base, chip->base + chip->ngpio - 1,
@@ -429,15 +501,18 @@
*/
void gpiochip_remove(struct gpio_chip *chip)
{
+ struct gpio_device *gdev = chip->gpiodev;
struct gpio_desc *desc;
unsigned long flags;
unsigned id;
bool requested = false;
+ /* Numb the device, cancelling all outstanding operations */
+ gdev->chip = NULL;
+
+ /* FIXME: should the legacy sysfs handling be moved to gpio_device? */
gpiochip_sysfs_unregister(chip);
-
gpiochip_irqchip_remove(chip);
-
acpi_gpiochip_remove(chip);
gpiochip_remove_pin_ranges(chip);
gpiochip_free_hogs(chip);
@@ -450,15 +525,23 @@
if (test_bit(FLAG_REQUESTED, &desc->flags))
requested = true;
}
- list_del(&chip->list);
spin_unlock_irqrestore(&gpio_lock, flags);
if (requested)
dev_crit(chip->parent,
"REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
+ /* FIXME: need to be moved to gpio_device and held there */
kfree(chip->desc);
chip->desc = NULL;
+
+ /*
+ * The gpiochip side puts its use of the device to rest here:
+ * if there are no userspace clients, the chardev and device will
+ * be removed, else it will be dangling until the last user is
+ * gone.
+ */
+ put_device(&gdev->dev);
}
EXPORT_SYMBOL_GPL(gpiochip_remove);
@@ -477,17 +560,21 @@
int (*match)(struct gpio_chip *chip,
void *data))
{
+ struct gpio_device *gdev;
struct gpio_chip *chip;
unsigned long flags;
spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(chip, &gpio_chips, list)
- if (match(chip, data))
+ list_for_each_entry(gdev, &gpio_devices, list)
+ if (match(gdev->chip, data))
break;
/* No match? */
- if (&chip->list == &gpio_chips)
+ if (&gdev->list == &gpio_devices)
chip = NULL;
+ else
+ chip = gdev->chip;
+
spin_unlock_irqrestore(&gpio_lock, flags);
return chip;
@@ -617,14 +704,14 @@
{
struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
- if (!try_module_get(chip->owner))
+ if (!try_module_get(chip->gpiodev->owner))
return -ENODEV;
if (gpiochip_lock_as_irq(chip, d->hwirq)) {
chip_err(chip,
"unable to lock HW IRQ %lu for IRQ\n",
d->hwirq);
- module_put(chip->owner);
+ module_put(chip->gpiodev->owner);
return -EINVAL;
}
return 0;
@@ -635,7 +722,7 @@
struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
gpiochip_unlock_as_irq(chip, d->hwirq);
- module_put(chip->owner);
+ module_put(chip->gpiodev->owner);
}
static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
@@ -985,10 +1072,10 @@
if (!chip)
goto done;
- if (try_module_get(chip->owner)) {
+ if (try_module_get(chip->gpiodev->owner)) {
status = __gpiod_request(desc, label);
if (status < 0)
- module_put(chip->owner);
+ module_put(chip->gpiodev->owner);
}
done:
@@ -1034,7 +1121,7 @@
void gpiod_free(struct gpio_desc *desc)
{
if (desc && __gpiod_free(desc))
- module_put(desc->chip->owner);
+ module_put(desc->chip->gpiodev->owner);
else
WARN_ON(extra_checks);
}
@@ -2492,16 +2579,16 @@
static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
{
unsigned long flags;
- struct gpio_chip *chip = NULL;
+ struct gpio_device *gdev = NULL;
loff_t index = *pos;
s->private = "";
spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(chip, &gpio_chips, list)
+ list_for_each_entry(gdev, &gpio_devices, list)
if (index-- == 0) {
spin_unlock_irqrestore(&gpio_lock, flags);
- return chip;
+ return gdev;
}
spin_unlock_irqrestore(&gpio_lock, flags);
@@ -2511,14 +2598,14 @@
static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
unsigned long flags;
- struct gpio_chip *chip = v;
+ struct gpio_device *gdev = v;
void *ret = NULL;
spin_lock_irqsave(&gpio_lock, flags);
- if (list_is_last(&chip->list, &gpio_chips))
+ if (list_is_last(&gdev->list, &gpio_devices))
ret = NULL;
else
- ret = list_entry(chip->list.next, struct gpio_chip, list);
+ ret = list_entry(gdev->list.next, struct gpio_device, list);
spin_unlock_irqrestore(&gpio_lock, flags);
s->private = "\n";
@@ -2533,15 +2620,24 @@
static int gpiolib_seq_show(struct seq_file *s, void *v)
{
- struct gpio_chip *chip = v;
- struct device *dev;
+ struct gpio_device *gdev = v;
+ struct gpio_chip *chip = gdev->chip;
+ struct device *parent;
- seq_printf(s, "%sGPIOs %d-%d", (char *)s->private,
- chip->base, chip->base + chip->ngpio - 1);
- dev = chip->parent;
- if (dev)
- seq_printf(s, ", %s/%s", dev->bus ? dev->bus->name : "no-bus",
- dev_name(dev));
+ if (!chip) {
+ seq_printf(s, "%s%s: (dangling chip)", (char *)s->private,
+ dev_name(&gdev->dev));
+ return 0;
+ }
+
+ seq_printf(s, "%s%s: GPIOs %d-%d", (char *)s->private,
+ dev_name(&gdev->dev),
+ chip->base, chip->base + chip->ngpio - 1);
+ parent = chip->parent;
+ if (parent)
+ seq_printf(s, ", parent: %s/%s",
+ parent->bus ? parent->bus->name : "no-bus",
+ dev_name(parent));
if (chip->label)
seq_printf(s, ", %s", chip->label);
if (chip->can_sleep)
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 99ed3b0..feea2c8 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -12,14 +12,39 @@
#ifndef GPIOLIB_H
#define GPIOLIB_H
+#include <linux/gpio/driver.h>
#include <linux/err.h>
#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
enum of_gpio_flags;
enum gpiod_flags;
struct acpi_device;
/**
+ * struct gpio_device - internal state container for GPIO devices
+ * @id: numerical ID number for the GPIO chip
+ * @dev: the GPIO device struct
+ * @owner: helps prevent removal of modules exporting active GPIOs
+ * @chip: pointer to the corresponding gpiochip, holding static
+ * data for this device
+ * @list: links gpio_device:s together for traversal
+ *
+ * This state container holds most of the runtime variable data
+ * for a GPIO device and can hold references and live on after the
+ * GPIO chip has been removed, if it is still being used from
+ * userspace.
+ */
+struct gpio_device {
+ int id;
+ struct device dev;
+ struct module *owner;
+ struct gpio_chip *chip;
+ struct list_head list;
+};
+
+/**
* struct acpi_gpio_info - ACPI GPIO specific information
* @gpioint: if %true this GPIO is of type GpioInt otherwise type is GpioIo
* @active_low: in case of @gpioint, the pin is active low
@@ -90,7 +115,7 @@
struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip, u16 hwnum);
extern struct spinlock gpio_lock;
-extern struct list_head gpio_chips;
+extern struct list_head gpio_devices;
struct gpio_desc {
struct gpio_chip *chip;