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Message-ID: <20260116081036.352286-14-tzungbi@kernel.org>
Date: Fri, 16 Jan 2026 08:10:26 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Benson Leung <bleung@...omium.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Danilo Krummrich <dakr@...nel.org>,
Bartosz Golaszewski <brgl@...ev.pl>,
Linus Walleij <linusw@...nel.org>
Cc: Jonathan Corbet <corbet@....net>,
Shuah Khan <shuah@...nel.org>,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
chrome-platform@...ts.linux.dev,
linux-kselftest@...r.kernel.org,
tzungbi@...nel.org,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Simona Vetter <simona.vetter@...ll.ch>,
Dan Williams <dan.j.williams@...el.com>,
Jason Gunthorpe <jgg@...dia.com>,
linux-gpio@...r.kernel.org
Subject: [PATCH 13/23] gpiolib: cdev: Leverage revocable for gpio_fileops
Struct gpio_device now provides a revocable provider to the underlying
struct gpio_chip. Leverage revocable for gpio_fileops so that it doesn't
need to handle the synchronization by accessing the SRCU explicitly.
Also, it's unneeded to hold a reference count to the struct gpio_device
while the file is opening. The struct gpio_device
(i.e., (struct gpio_chip *)->gpiodev)) is valid as long as struct
gpio_chip is valid.
Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
---
drivers/gpio/gpiolib-cdev.c | 87 ++++++++++++++++++++++---------------
1 file changed, 52 insertions(+), 35 deletions(-)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index e42cfdb47885..832a542c4f7a 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -22,6 +22,7 @@
#include <linux/overflow.h>
#include <linux/pinctrl/consumer.h>
#include <linux/poll.h>
+#include <linux/revocable.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/string.h>
@@ -2297,7 +2298,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
}
struct gpio_chardev_data {
- struct gpio_device *gdev;
+ struct revocable *chip_rev;
wait_queue_head_t wait;
DECLARE_KFIFO(events, struct gpio_v2_line_info_changed, 32);
struct notifier_block lineinfo_changed_nb;
@@ -2309,9 +2310,8 @@ struct gpio_chardev_data {
struct file *fp;
};
-static int chipinfo_get(struct gpio_chardev_data *cdev, void __user *ip)
+static int chipinfo_get(struct gpio_device *gdev, void __user *ip)
{
- struct gpio_device *gdev = cdev->gdev;
struct gpiochip_info chipinfo;
memset(&chipinfo, 0, sizeof(chipinfo));
@@ -2339,7 +2339,8 @@ static int lineinfo_ensure_abi_version(struct gpio_chardev_data *cdata,
return abiv;
}
-static int lineinfo_get_v1(struct gpio_chardev_data *cdev, void __user *ip,
+static int lineinfo_get_v1(struct gpio_chardev_data *cdev,
+ struct gpio_device *gdev, void __user *ip,
bool watch)
{
struct gpio_desc *desc;
@@ -2350,7 +2351,7 @@ static int lineinfo_get_v1(struct gpio_chardev_data *cdev, void __user *ip,
return -EFAULT;
/* this doubles as a range check on line_offset */
- desc = gpio_device_get_desc(cdev->gdev, lineinfo.line_offset);
+ desc = gpio_device_get_desc(gdev, lineinfo.line_offset);
if (IS_ERR(desc))
return PTR_ERR(desc);
@@ -2375,7 +2376,8 @@ static int lineinfo_get_v1(struct gpio_chardev_data *cdev, void __user *ip,
}
#endif
-static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
+static int lineinfo_get(struct gpio_chardev_data *cdev,
+ struct gpio_device *gdev, void __user *ip,
bool watch)
{
struct gpio_desc *desc;
@@ -2387,7 +2389,7 @@ static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
if (!mem_is_zero(lineinfo.padding, sizeof(lineinfo.padding)))
return -EINVAL;
- desc = gpio_device_get_desc(cdev->gdev, lineinfo.offset);
+ desc = gpio_device_get_desc(gdev, lineinfo.offset);
if (IS_ERR(desc))
return PTR_ERR(desc);
@@ -2410,14 +2412,15 @@ static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
return 0;
}
-static int lineinfo_unwatch(struct gpio_chardev_data *cdev, void __user *ip)
+static int lineinfo_unwatch(struct gpio_chardev_data *cdev,
+ struct gpio_device *gdev, void __user *ip)
{
__u32 offset;
if (copy_from_user(&offset, ip, sizeof(offset)))
return -EFAULT;
- if (offset >= cdev->gdev->ngpio)
+ if (offset >= gdev->ngpio)
return -EINVAL;
if (!test_and_clear_bit(offset, cdev->watched_lines))
@@ -2432,37 +2435,38 @@ static int lineinfo_unwatch(struct gpio_chardev_data *cdev, void __user *ip)
static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct gpio_chardev_data *cdev = file->private_data;
- struct gpio_device *gdev = cdev->gdev;
+ struct gpio_chip *gc;
+ struct gpio_device *gdev;
void __user *ip = (void __user *)arg;
- guard(srcu)(&gdev->srcu);
-
/* We fail any subsequent ioctl():s when the chip is gone */
- if (!rcu_access_pointer(gdev->chip))
+ REVOCABLE_TRY_ACCESS_WITH(cdev->chip_rev, gc);
+ if (!gc)
return -ENODEV;
+ gdev = gc->gpiodev;
/* Fill in the struct and pass to userspace */
switch (cmd) {
case GPIO_GET_CHIPINFO_IOCTL:
- return chipinfo_get(cdev, ip);
+ return chipinfo_get(gdev, ip);
#ifdef CONFIG_GPIO_CDEV_V1
case GPIO_GET_LINEHANDLE_IOCTL:
return linehandle_create(gdev, ip);
case GPIO_GET_LINEEVENT_IOCTL:
return lineevent_create(gdev, ip);
case GPIO_GET_LINEINFO_IOCTL:
- return lineinfo_get_v1(cdev, ip, false);
+ return lineinfo_get_v1(cdev, gdev, ip, false);
case GPIO_GET_LINEINFO_WATCH_IOCTL:
- return lineinfo_get_v1(cdev, ip, true);
+ return lineinfo_get_v1(cdev, gdev, ip, true);
#endif /* CONFIG_GPIO_CDEV_V1 */
case GPIO_V2_GET_LINEINFO_IOCTL:
- return lineinfo_get(cdev, ip, false);
+ return lineinfo_get(cdev, gdev, ip, false);
case GPIO_V2_GET_LINEINFO_WATCH_IOCTL:
- return lineinfo_get(cdev, ip, true);
+ return lineinfo_get(cdev, gdev, ip, true);
case GPIO_V2_GET_LINE_IOCTL:
return linereq_create(gdev, ip);
case GPIO_GET_LINEINFO_UNWATCH_IOCTL:
- return lineinfo_unwatch(cdev, ip);
+ return lineinfo_unwatch(cdev, gdev, ip);
default:
return -EINVAL;
}
@@ -2585,10 +2589,10 @@ static __poll_t lineinfo_watch_poll(struct file *file,
{
struct gpio_chardev_data *cdev = file->private_data;
__poll_t events = 0;
+ struct gpio_chip *gc;
- guard(srcu)(&cdev->gdev->srcu);
-
- if (!rcu_access_pointer(cdev->gdev->chip))
+ REVOCABLE_TRY_ACCESS_WITH(cdev->chip_rev, gc);
+ if (!gc)
return EPOLLHUP | EPOLLERR;
poll_wait(file, &cdev->wait, pollt);
@@ -2608,10 +2612,10 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
ssize_t bytes_read = 0;
int ret;
size_t event_size;
+ struct gpio_chip *gc;
- guard(srcu)(&cdev->gdev->srcu);
-
- if (!rcu_access_pointer(cdev->gdev->chip))
+ REVOCABLE_TRY_ACCESS_WITH(cdev->chip_rev, gc);
+ if (!gc)
return -ENODEV;
#ifndef CONFIG_GPIO_CDEV_V1
@@ -2695,13 +2699,16 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
if (!cdev)
return -ENOMEM;
+ cdev->chip_rev = revocable_alloc(gdev->chip_rp);
+ if (!cdev->chip_rev)
+ goto out_free_cdev;
+
cdev->watched_lines = bitmap_zalloc(gdev->ngpio, GFP_KERNEL);
if (!cdev->watched_lines)
- goto out_free_cdev;
+ goto out_free_chip_rev;
init_waitqueue_head(&cdev->wait);
INIT_KFIFO(cdev->events);
- cdev->gdev = gpio_device_get(gdev);
cdev->lineinfo_changed_nb.notifier_call = lineinfo_changed_notify;
scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
@@ -2734,8 +2741,9 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
raw_notifier_chain_unregister(&gdev->line_state_notifier,
&cdev->lineinfo_changed_nb);
out_free_bitmap:
- gpio_device_put(gdev);
bitmap_free(cdev->watched_lines);
+out_free_chip_rev:
+ revocable_free(cdev->chip_rev);
out_free_cdev:
kfree(cdev);
return ret;
@@ -2752,15 +2760,24 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
static int gpio_chrdev_release(struct inode *inode, struct file *file)
{
struct gpio_chardev_data *cdev = file->private_data;
- struct gpio_device *gdev = cdev->gdev;
+ struct gpio_chip *gc;
+ struct gpio_device *gdev;
+
+ REVOCABLE_TRY_ACCESS_SCOPED(cdev->chip_rev, gc) {
+ if (!gc)
+ break;
+ gdev = gc->gpiodev;
+
+ blocking_notifier_chain_unregister(&gdev->device_notifier,
+ &cdev->device_unregistered_nb);
+
+ scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
+ raw_notifier_chain_unregister(&gdev->line_state_notifier,
+ &cdev->lineinfo_changed_nb);
+ }
+ revocable_free(cdev->chip_rev);
- blocking_notifier_chain_unregister(&gdev->device_notifier,
- &cdev->device_unregistered_nb);
- scoped_guard(write_lock_irqsave, &gdev->line_state_lock)
- raw_notifier_chain_unregister(&gdev->line_state_notifier,
- &cdev->lineinfo_changed_nb);
bitmap_free(cdev->watched_lines);
- gpio_device_put(gdev);
kfree(cdev);
return 0;
--
2.52.0.457.g6b5491de43-goog
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