linux/drivers/gpio/gpiolib-sysfs.c

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// SPDX-License-Identifier: GPL-2.0
#include <linux/bitops.h>
#include <linux/cleanup.h>
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kdev_t.h>
#include <linux/kstrtox.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/srcu.h>
#include <linux/sysfs.h>
#include <linux/types.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include "gpiolib.h"
#include "gpiolib-sysfs.h"
struct kernfs_node;
#define GPIO_IRQF_TRIGGER_NONE 0
#define GPIO_IRQF_TRIGGER_FALLING BIT(0)
#define GPIO_IRQF_TRIGGER_RISING BIT(1)
#define GPIO_IRQF_TRIGGER_BOTH (GPIO_IRQF_TRIGGER_FALLING | \
GPIO_IRQF_TRIGGER_RISING)
struct gpiod_data {
struct gpio_desc *desc;
struct mutex mutex;
struct kernfs_node *value_kn;
int irq;
unsigned char irq_flags;
bool direction_can_change;
};
/*
* Lock to serialise gpiod export and unexport, and prevent re-export of
* gpiod whose chip is being unregistered.
*/
static DEFINE_MUTEX(sysfs_lock);
/*
* /sys/class/gpio/gpioN... only for GPIOs that are exported
* /direction
* * MAY BE OMITTED if kernel won't allow direction changes
* * is read/write as "in" or "out"
* * may also be written as "high" or "low", initializing
* output value as specified ("out" implies "low")
* /value
* * always readable, subject to hardware behavior
* * may be writable, as zero/nonzero
* /edge
* * configures behavior of poll(2) on /value
* * available only if pin can generate IRQs on input
* * is read/write as "none", "falling", "rising", or "both"
* /active_low
* * configures polarity of /value
* * is read/write as zero/nonzero
* * also affects existing and subsequent "falling" and "rising"
* /edge configuration
*/
static ssize_t direction_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
int value;
mutex_lock(&data->mutex);
gpiod_get_direction(desc);
value = !!test_bit(FLAG_IS_OUT, &desc->flags);
mutex_unlock(&data->mutex);
return sysfs_emit(buf, "%s\n", value ? "out" : "in");
}
static ssize_t direction_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
ssize_t status;
mutex_lock(&data->mutex);
if (sysfs_streq(buf, "high"))
status = gpiod_direction_output_raw(desc, 1);
else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
status = gpiod_direction_output_raw(desc, 0);
else if (sysfs_streq(buf, "in"))
status = gpiod_direction_input(desc);
else
status = -EINVAL;
mutex_unlock(&data->mutex);
return status ? : size;
}
static DEVICE_ATTR_RW(direction);
static ssize_t value_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
ssize_t status;
mutex_lock(&data->mutex);
status = gpiod_get_value_cansleep(desc);
mutex_unlock(&data->mutex);
if (status < 0)
return status;
return sysfs_emit(buf, "%zd\n", status);
}
static ssize_t value_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
ssize_t status;
long value;
status = kstrtol(buf, 0, &value);
mutex_lock(&data->mutex);
if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
status = -EPERM;
} else if (status == 0) {
gpiod_set_value_cansleep(desc, value);
status = size;
}
mutex_unlock(&data->mutex);
return status;
}
static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store);
static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
{
struct gpiod_data *data = priv;
sysfs_notify_dirent(data->value_kn);
return IRQ_HANDLED;
}
/* Caller holds gpiod-data mutex. */
static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
unsigned long irq_flags;
int ret;
CLASS(gpio_chip_guard, guard)(desc);
if (!guard.gc)
return -ENODEV;
data->irq = gpiod_to_irq(desc);
if (data->irq < 0)
return -EIO;
data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
if (!data->value_kn)
return -ENODEV;
irq_flags = IRQF_SHARED;
if (flags & GPIO_IRQF_TRIGGER_FALLING)
irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
if (flags & GPIO_IRQF_TRIGGER_RISING)
irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
/*
* FIXME: This should be done in the irq_request_resources callback
* when the irq is requested, but a few drivers currently fail
* to do so.
*
* Remove this redundant call (along with the corresponding
* unlock) when those drivers have been fixed.
*/
ret = gpiochip_lock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
if (ret < 0)
goto err_put_kn;
ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
"gpiolib", data);
if (ret < 0)
goto err_unlock;
data->irq_flags = flags;
return 0;
err_unlock:
gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
err_put_kn:
sysfs_put(data->value_kn);
return ret;
}
/*
* Caller holds gpiod-data mutex (unless called after class-device
* deregistration).
*/
static void gpio_sysfs_free_irq(struct device *dev)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
CLASS(gpio_chip_guard, guard)(desc);
if (!guard.gc)
return;
data->irq_flags = 0;
free_irq(data->irq, data);
gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
sysfs_put(data->value_kn);
}
static const char * const trigger_names[] = {
[GPIO_IRQF_TRIGGER_NONE] = "none",
[GPIO_IRQF_TRIGGER_FALLING] = "falling",
[GPIO_IRQF_TRIGGER_RISING] = "rising",
[GPIO_IRQF_TRIGGER_BOTH] = "both",
};
static ssize_t edge_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gpiod_data *data = dev_get_drvdata(dev);
int flags;
mutex_lock(&data->mutex);
flags = data->irq_flags;
mutex_unlock(&data->mutex);
if (flags >= ARRAY_SIZE(trigger_names))
return 0;
return sysfs_emit(buf, "%s\n", trigger_names[flags]);
}
static ssize_t edge_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct gpiod_data *data = dev_get_drvdata(dev);
ssize_t status = size;
int flags;
flags = sysfs_match_string(trigger_names, buf);
if (flags < 0)
return flags;
mutex_lock(&data->mutex);
if (flags == data->irq_flags) {
status = size;
goto out_unlock;
}
if (data->irq_flags)
gpio_sysfs_free_irq(dev);
if (flags) {
status = gpio_sysfs_request_irq(dev, flags);
if (!status)
status = size;
}
out_unlock:
mutex_unlock(&data->mutex);
return status;
}
static DEVICE_ATTR_RW(edge);
/* Caller holds gpiod-data mutex. */
static int gpio_sysfs_set_active_low(struct device *dev, int value)
{
struct gpiod_data *data = dev_get_drvdata(dev);
unsigned int flags = data->irq_flags;
struct gpio_desc *desc = data->desc;
int status = 0;
if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
return 0;
assign_bit(FLAG_ACTIVE_LOW, &desc->flags, value);
/* reconfigure poll(2) support if enabled on one edge only */
if (flags == GPIO_IRQF_TRIGGER_FALLING ||
flags == GPIO_IRQF_TRIGGER_RISING) {
gpio_sysfs_free_irq(dev);
status = gpio_sysfs_request_irq(dev, flags);
}
return status;
}
static ssize_t active_low_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
int value;
mutex_lock(&data->mutex);
value = !!test_bit(FLAG_ACTIVE_LOW, &desc->flags);
mutex_unlock(&data->mutex);
return sysfs_emit(buf, "%d\n", value);
}
static ssize_t active_low_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t size)
{
struct gpiod_data *data = dev_get_drvdata(dev);
ssize_t status;
long value;
status = kstrtol(buf, 0, &value);
if (status)
return status;
mutex_lock(&data->mutex);
status = gpio_sysfs_set_active_low(dev, value);
mutex_unlock(&data->mutex);
return status ? : size;
}
static DEVICE_ATTR_RW(active_low);
static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
int n)
{
struct device *dev = kobj_to_dev(kobj);
struct gpiod_data *data = dev_get_drvdata(dev);
struct gpio_desc *desc = data->desc;
umode_t mode = attr->mode;
bool show_direction = data->direction_can_change;
if (attr == &dev_attr_direction.attr) {
if (!show_direction)
mode = 0;
} else if (attr == &dev_attr_edge.attr) {
if (gpiod_to_irq(desc) < 0)
mode = 0;
if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
mode = 0;
}
return mode;
}
static struct attribute *gpio_attrs[] = {
&dev_attr_direction.attr,
&dev_attr_edge.attr,
&dev_attr_value.attr,
&dev_attr_active_low.attr,
NULL,
};
static const struct attribute_group gpio_group = {
.attrs = gpio_attrs,
.is_visible = gpio_is_visible,
};
static const struct attribute_group *gpio_groups[] = {
&gpio_group,
NULL
};
/*
* /sys/class/gpio/gpiochipN/
* /base ... matching gpio_chip.base (N)
* /label ... matching gpio_chip.label
* /ngpio ... matching gpio_chip.ngpio
*/
static ssize_t base_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
const struct gpio_device *gdev = dev_get_drvdata(dev);
return sysfs_emit(buf, "%u\n", gdev->base);
}
static DEVICE_ATTR_RO(base);
static ssize_t label_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
const struct gpio_device *gdev = dev_get_drvdata(dev);
return sysfs_emit(buf, "%s\n", gdev->label);
}
static DEVICE_ATTR_RO(label);
static ssize_t ngpio_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
const struct gpio_device *gdev = dev_get_drvdata(dev);
return sysfs_emit(buf, "%u\n", gdev->ngpio);
}
static DEVICE_ATTR_RO(ngpio);
static struct attribute *gpiochip_attrs[] = {
&dev_attr_base.attr,
&dev_attr_label.attr,
&dev_attr_ngpio.attr,
NULL,
};
ATTRIBUTE_GROUPS(gpiochip);
/*
* /sys/class/gpio/export ... write-only
* integer N ... number of GPIO to export (full access)
* /sys/class/gpio/unexport ... write-only
* integer N ... number of GPIO to unexport
*/
driver core: class: mark the struct class for sysfs callbacks as constant struct class should never be modified in a sysfs callback as there is nothing in the structure to modify, and frankly, the structure is almost never used in a sysfs callback, so mark it as constant to allow struct class to be moved to read-only memory. While we are touching all class sysfs callbacks also mark the attribute as constant as it can not be modified. The bonding code still uses this structure so it can not be removed from the function callbacks. Cc: "David S. Miller" <davem@davemloft.net> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Bartosz Golaszewski <brgl@bgdev.pl> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Miquel Raynal <miquel.raynal@bootlin.com> Cc: Namjae Jeon <linkinjeon@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Russ Weight <russell.h.weight@intel.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steve French <sfrench@samba.org> Cc: Vignesh Raghavendra <vigneshr@ti.com> Cc: linux-cifs@vger.kernel.org Cc: linux-gpio@vger.kernel.org Cc: linux-mtd@lists.infradead.org Cc: linux-rdma@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: netdev@vger.kernel.org Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Link: https://lore.kernel.org/r/20230325084537.3622280-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-25 09:45:37 +01:00
static ssize_t export_store(const struct class *class,
const struct class_attribute *attr,
const char *buf, size_t len)
{
struct gpio_desc *desc;
int status, offset;
long gpio;
status = kstrtol(buf, 0, &gpio);
if (status)
return status;
desc = gpio_to_desc(gpio);
/* reject invalid GPIOs */
if (!desc) {
pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
return -EINVAL;
}
CLASS(gpio_chip_guard, guard)(desc);
if (!guard.gc)
return -ENODEV;
offset = gpio_chip_hwgpio(desc);
if (!gpiochip_line_is_valid(guard.gc, offset)) {
pr_warn("%s: GPIO %ld masked\n", __func__, gpio);
return -EINVAL;
}
/* No extra locking here; FLAG_SYSFS just signifies that the
* request and export were done by on behalf of userspace, so
* they may be undone on its behalf too.
*/
status = gpiod_request_user(desc, "sysfs");
if (status)
goto done;
status = gpiod_set_transitory(desc, false);
if (status) {
gpiod_free(desc);
goto done;
}
status = gpiod_export(desc, true);
if (status < 0)
gpiod_free(desc);
else
set_bit(FLAG_SYSFS, &desc->flags);
done:
if (status)
pr_debug("%s: status %d\n", __func__, status);
return status ? : len;
}
static CLASS_ATTR_WO(export);
driver core: class: mark the struct class for sysfs callbacks as constant struct class should never be modified in a sysfs callback as there is nothing in the structure to modify, and frankly, the structure is almost never used in a sysfs callback, so mark it as constant to allow struct class to be moved to read-only memory. While we are touching all class sysfs callbacks also mark the attribute as constant as it can not be modified. The bonding code still uses this structure so it can not be removed from the function callbacks. Cc: "David S. Miller" <davem@davemloft.net> Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Bartosz Golaszewski <brgl@bgdev.pl> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Linus Walleij <linus.walleij@linaro.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Miquel Raynal <miquel.raynal@bootlin.com> Cc: Namjae Jeon <linkinjeon@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Russ Weight <russell.h.weight@intel.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steve French <sfrench@samba.org> Cc: Vignesh Raghavendra <vigneshr@ti.com> Cc: linux-cifs@vger.kernel.org Cc: linux-gpio@vger.kernel.org Cc: linux-mtd@lists.infradead.org Cc: linux-rdma@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: netdev@vger.kernel.org Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Link: https://lore.kernel.org/r/20230325084537.3622280-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-03-25 09:45:37 +01:00
static ssize_t unexport_store(const struct class *class,
const struct class_attribute *attr,
const char *buf, size_t len)
{
struct gpio_desc *desc;
int status;
long gpio;
status = kstrtol(buf, 0, &gpio);
if (status < 0)
goto done;
desc = gpio_to_desc(gpio);
/* reject bogus commands (gpiod_unexport() ignores them) */
if (!desc) {
pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
return -EINVAL;
}
status = -EINVAL;
/* No extra locking here; FLAG_SYSFS just signifies that the
* request and export were done by on behalf of userspace, so
* they may be undone on its behalf too.
*/
if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
gpiod_unexport(desc);
gpiod_free(desc);
status = 0;
}
done:
if (status)
pr_debug("%s: status %d\n", __func__, status);
return status ? : len;
}
static CLASS_ATTR_WO(unexport);
static struct attribute *gpio_class_attrs[] = {
&class_attr_export.attr,
&class_attr_unexport.attr,
NULL,
};
ATTRIBUTE_GROUPS(gpio_class);
static struct class gpio_class = {
.name = "gpio",
.class_groups = gpio_class_groups,
};
/**
* gpiod_export - export a GPIO through sysfs
* @desc: GPIO to make available, already requested
* @direction_may_change: true if userspace may change GPIO direction
* Context: arch_initcall or later
*
* When drivers want to make a GPIO accessible to userspace after they
* have requested it -- perhaps while debugging, or as part of their
* public interface -- they may use this routine. If the GPIO can
* change direction (some can't) and the caller allows it, userspace
* will see "direction" sysfs attribute which may be used to change
* the gpio's direction. A "value" attribute will always be provided.
*
* Returns zero on success, else an error.
*/
int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
{
const char *ioname = NULL;
struct gpio_device *gdev;
struct gpiod_data *data;
struct device *dev;
int status, offset;
/* can't export until sysfs is available ... */
if (!class_is_registered(&gpio_class)) {
pr_debug("%s: called too early!\n", __func__);
return -ENOENT;
}
if (!desc) {
pr_debug("%s: invalid gpio descriptor\n", __func__);
return -EINVAL;
}
CLASS(gpio_chip_guard, guard)(desc);
if (!guard.gc)
return -ENODEV;
if (test_and_set_bit(FLAG_EXPORT, &desc->flags))
gpio: remove gpio_lock The "multi-function" gpio_lock is pretty much useless with how it's used in GPIOLIB currently. Because many GPIO API calls can be called from all contexts but may also call into sleeping driver callbacks, there are many places with utterly broken workarounds like yielding the lock to call a possibly sleeping function and then re-acquiring it again without taking into account that the protected state may have changed. It was also used to protect several unrelated things: like individual descriptors AND the GPIO device list. We now serialize access to these two with SRCU and so can finally remove the spinlock. There is of course the question of consistency of lockless access to GPIO descriptors. Because we only support exclusive access to GPIOs (officially anyway, I'm looking at you broken GPIOD_FLAGS_BIT_NONEXCLUSIVE bit...) and the API contract with providers does not guarantee serialization, it's enough to ensure we cannot accidentally dereference an invalid pointer and that the state we present to both users and providers remains consistent. To achieve that: read the flags field atomically except for a few special cases. Read their current value before executing callback code and use this value for any subsequent logic. Modifying the flags depends on the particular use-case and can differ. For instance: when requesting a GPIO, we need to set the REQUESTED bit immediately so that the next user trying to request the same line sees -EBUSY. While at it: the allocations that used GFP_ATOMIC until this point can now switch to GFP_KERNEL. Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
2024-01-12 14:49:04 +01:00
return -EPERM;
gpio: reflect base and ngpio into gpio_device Some information about the GPIO chip need to stay around also after the gpio_chip has been removed and only the gpio_device persist. The base and ngpio are such things, for example we don't want a new chip arriving to overlap the number space of a dangling gpio_device, and the chardev may still query the device for the number of lines etc. Note that the code that assigns base and insert gpio_device into the global list no longer check for a missing gpio_chip: we respect the number space allocated by any other gpio_device. As a consequence of the gdev being referenced directly from the gpio_desc, we need to verify it differently from all in-kernel API calls that fall through to direct queries to the gpio_chip vtable: we first check that desc is !NULL, then that desc->gdev is !NULL, then, if desc->gdev->chip is NULL, we *BAIL OUT* without any error, so as to manage the case where operations are requested on a device that is gone. These checks were non-uniform and partly missing in the past: so to simplify: create the macros VALIDATE_DESC() that will return -EINVAL if the desc or desc->gdev is missing and just 0 if the chip is gone, and conversely VALIDATE_DESC_VOID() for the case where the function does not return an error. By using these macros, we get warning messages about missing gdev with reference to the right function in the kernel log. Despite the macro business this simplifies the code and make it more readable than if we copy/paste the same descriptor checking code into all code ABI call sites (IMHO). Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2016-02-10 10:57:36 +01:00
gdev = desc->gdev;
mutex_lock(&sysfs_lock);
/* check if chip is being removed */
if (!gdev->mockdev) {
status = -ENODEV;
goto err_unlock;
}
gpio: remove gpio_lock The "multi-function" gpio_lock is pretty much useless with how it's used in GPIOLIB currently. Because many GPIO API calls can be called from all contexts but may also call into sleeping driver callbacks, there are many places with utterly broken workarounds like yielding the lock to call a possibly sleeping function and then re-acquiring it again without taking into account that the protected state may have changed. It was also used to protect several unrelated things: like individual descriptors AND the GPIO device list. We now serialize access to these two with SRCU and so can finally remove the spinlock. There is of course the question of consistency of lockless access to GPIO descriptors. Because we only support exclusive access to GPIOs (officially anyway, I'm looking at you broken GPIOD_FLAGS_BIT_NONEXCLUSIVE bit...) and the API contract with providers does not guarantee serialization, it's enough to ensure we cannot accidentally dereference an invalid pointer and that the state we present to both users and providers remains consistent. To achieve that: read the flags field atomically except for a few special cases. Read their current value before executing callback code and use this value for any subsequent logic. Modifying the flags depends on the particular use-case and can differ. For instance: when requesting a GPIO, we need to set the REQUESTED bit immediately so that the next user trying to request the same line sees -EBUSY. While at it: the allocations that used GFP_ATOMIC until this point can now switch to GFP_KERNEL. Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
2024-01-12 14:49:04 +01:00
if (!test_bit(FLAG_REQUESTED, &desc->flags)) {
gpiod_dbg(desc, "%s: unavailable (not requested)\n", __func__);
status = -EPERM;
goto err_unlock;
}
data = kzalloc(sizeof(*data), GFP_KERNEL);
if (!data) {
status = -ENOMEM;
goto err_unlock;
}
data->desc = desc;
mutex_init(&data->mutex);
if (guard.gc->direction_input && guard.gc->direction_output)
data->direction_can_change = direction_may_change;
else
data->direction_can_change = false;
offset = gpio_chip_hwgpio(desc);
if (guard.gc->names && guard.gc->names[offset])
ioname = guard.gc->names[offset];
dev = device_create_with_groups(&gpio_class, &gdev->dev,
MKDEV(0, 0), data, gpio_groups,
ioname ? ioname : "gpio%u",
desc_to_gpio(desc));
if (IS_ERR(dev)) {
status = PTR_ERR(dev);
goto err_free_data;
}
mutex_unlock(&sysfs_lock);
return 0;
err_free_data:
kfree(data);
err_unlock:
mutex_unlock(&sysfs_lock);
gpio: remove gpio_lock The "multi-function" gpio_lock is pretty much useless with how it's used in GPIOLIB currently. Because many GPIO API calls can be called from all contexts but may also call into sleeping driver callbacks, there are many places with utterly broken workarounds like yielding the lock to call a possibly sleeping function and then re-acquiring it again without taking into account that the protected state may have changed. It was also used to protect several unrelated things: like individual descriptors AND the GPIO device list. We now serialize access to these two with SRCU and so can finally remove the spinlock. There is of course the question of consistency of lockless access to GPIO descriptors. Because we only support exclusive access to GPIOs (officially anyway, I'm looking at you broken GPIOD_FLAGS_BIT_NONEXCLUSIVE bit...) and the API contract with providers does not guarantee serialization, it's enough to ensure we cannot accidentally dereference an invalid pointer and that the state we present to both users and providers remains consistent. To achieve that: read the flags field atomically except for a few special cases. Read their current value before executing callback code and use this value for any subsequent logic. Modifying the flags depends on the particular use-case and can differ. For instance: when requesting a GPIO, we need to set the REQUESTED bit immediately so that the next user trying to request the same line sees -EBUSY. While at it: the allocations that used GFP_ATOMIC until this point can now switch to GFP_KERNEL. Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
2024-01-12 14:49:04 +01:00
clear_bit(FLAG_EXPORT, &desc->flags);
gpiod_dbg(desc, "%s: status %d\n", __func__, status);
return status;
}
EXPORT_SYMBOL_GPL(gpiod_export);
static int match_export(struct device *dev, const void *desc)
{
struct gpiod_data *data = dev_get_drvdata(dev);
return data->desc == desc;
}
/**
* gpiod_export_link - create a sysfs link to an exported GPIO node
* @dev: device under which to create symlink
* @name: name of the symlink
* @desc: GPIO to create symlink to, already exported
*
* Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
* node. Caller is responsible for unlinking.
*
* Returns zero on success, else an error.
*/
int gpiod_export_link(struct device *dev, const char *name,
struct gpio_desc *desc)
{
struct device *cdev;
int ret;
if (!desc) {
pr_warn("%s: invalid GPIO\n", __func__);
return -EINVAL;
}
cdev = class_find_device(&gpio_class, NULL, desc, match_export);
if (!cdev)
return -ENODEV;
ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);
put_device(cdev);
return ret;
}
EXPORT_SYMBOL_GPL(gpiod_export_link);
/**
* gpiod_unexport - reverse effect of gpiod_export()
* @desc: GPIO to make unavailable
*
* This is implicit on gpiod_free().
*/
void gpiod_unexport(struct gpio_desc *desc)
{
struct gpiod_data *data;
struct device *dev;
if (!desc) {
pr_warn("%s: invalid GPIO\n", __func__);
return;
}
mutex_lock(&sysfs_lock);
if (!test_bit(FLAG_EXPORT, &desc->flags))
goto err_unlock;
dev = class_find_device(&gpio_class, NULL, desc, match_export);
if (!dev)
goto err_unlock;
data = dev_get_drvdata(dev);
clear_bit(FLAG_EXPORT, &desc->flags);
device_unregister(dev);
/*
* Release irq after deregistration to prevent race with edge_store.
*/
if (data->irq_flags)
gpio_sysfs_free_irq(dev);
mutex_unlock(&sysfs_lock);
put_device(dev);
kfree(data);
return;
err_unlock:
mutex_unlock(&sysfs_lock);
}
EXPORT_SYMBOL_GPL(gpiod_unexport);
int gpiochip_sysfs_register(struct gpio_device *gdev)
{
struct gpio_chip *chip;
struct device *parent;
struct device *dev;
/*
* Many systems add gpio chips for SOC support very early,
* before driver model support is available. In those cases we
* register later, in gpiolib_sysfs_init() ... here we just
* verify that _some_ field of gpio_class got initialized.
*/
if (!class_is_registered(&gpio_class))
return 0;
guard(srcu)(&gdev->srcu);
chip = srcu_dereference(gdev->chip, &gdev->srcu);
if (!chip)
return -ENODEV;
/*
* For sysfs backward compatibility we need to preserve this
* preferred parenting to the gpio_chip parent field, if set.
*/
if (chip->parent)
parent = chip->parent;
else
parent = &gdev->dev;
/* use chip->base for the ID; it's already known to be unique */
dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), gdev,
gpiochip_groups, GPIOCHIP_NAME "%d",
chip->base);
if (IS_ERR(dev))
return PTR_ERR(dev);
mutex_lock(&sysfs_lock);
gdev->mockdev = dev;
mutex_unlock(&sysfs_lock);
return 0;
}
void gpiochip_sysfs_unregister(struct gpio_device *gdev)
{
struct gpio_desc *desc;
struct gpio_chip *chip;
scoped_guard(mutex, &sysfs_lock) {
if (!gdev->mockdev)
return;
device_unregister(gdev->mockdev);
/* prevent further gpiod exports */
gdev->mockdev = NULL;
}
guard(srcu)(&gdev->srcu);
chip = srcu_dereference(gdev->chip, &gdev->srcu);
if (!chip)
return;
/* unregister gpiod class devices owned by sysfs */
for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) {
gpiod_unexport(desc);
gpiod_free(desc);
}
}
/*
* We're not really looking for a device - we just want to iterate over the
* list and call this callback for each GPIO device. This is why this function
* always returns 0.
*/
static int gpiofind_sysfs_register(struct gpio_chip *gc, const void *data)
{
struct gpio_device *gdev = gc->gpiodev;
int ret;
if (gdev->mockdev)
return 0;
ret = gpiochip_sysfs_register(gdev);
if (ret)
chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
return 0;
}
static int __init gpiolib_sysfs_init(void)
{
int status;
status = class_register(&gpio_class);
if (status < 0)
return status;
/* Scan and register the gpio_chips which registered very
* early (e.g. before the class_register above was called).
*
* We run before arch_initcall() so chip->dev nodes can have
* registered, and so arch_initcall() can always gpiod_export().
*/
(void)gpio_device_find(NULL, gpiofind_sysfs_register);
return 0;
}
postcore_initcall(gpiolib_sysfs_init);