linux-kernel - [PATCH 14/23] gpiolib: cdev: Leverage revocable for linehandle

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Message-ID: <20260116081036.352286-15-tzungbi@kernel.org>
Date: Fri, 16 Jan 2026 08:10:27 +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 14/23] gpiolib: cdev: Leverage revocable for linehandle_fileops

Struct gpio_device now provides a revocable provider to the underlying
struct gpio_chip.  Leverage revocable for linehandle_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 | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 832a542c4f7a..f7c6f1367235 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -67,13 +67,13 @@ static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8));
 #ifdef CONFIG_GPIO_CDEV_V1
 /**
  * struct linehandle_state - contains the state of a userspace handle
- * @gdev: the GPIO device the handle pertains to
+ * @chip_rev: revocable consumer handle for the corresponding struct gpio_chip
  * @label: consumer label used to tag descriptors
  * @descs: the GPIO descriptors held by this handle
  * @num_descs: the number of descriptors held in the descs array
  */
 struct linehandle_state {
-	struct gpio_device *gdev;
+	struct revocable *chip_rev;
 	const char *label;
 	struct gpio_desc *descs[GPIOHANDLES_MAX];
 	u32 num_descs;
@@ -211,10 +211,10 @@ static long linehandle_ioctl(struct file *file, unsigned int cmd,
 	DECLARE_BITMAP(vals, GPIOHANDLES_MAX);
 	unsigned int i;
 	int ret;
+	struct gpio_chip *gc;
 
-	guard(srcu)(&lh->gdev->srcu);
-
-	if (!rcu_access_pointer(lh->gdev->chip))
+	REVOCABLE_TRY_ACCESS_WITH(lh->chip_rev, gc);
+	if (!gc)
 		return -ENODEV;
 
 	switch (cmd) {
@@ -279,7 +279,8 @@ static void linehandle_free(struct linehandle_state *lh)
 		if (lh->descs[i])
 			gpiod_free(lh->descs[i]);
 	kfree(lh->label);
-	gpio_device_put(lh->gdev);
+	if (lh->chip_rev)
+		revocable_free(lh->chip_rev);
 	kfree(lh);
 }
 
@@ -322,7 +323,10 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	lh = kzalloc(sizeof(*lh), GFP_KERNEL);
 	if (!lh)
 		return -ENOMEM;
-	lh->gdev = gpio_device_get(gdev);
+
+	lh->chip_rev = revocable_alloc(gdev->chip_rp);
+	if (!lh->chip_rev)
+		return -ENOMEM;
 
 	if (handlereq.consumer_label[0] != '\0') {
 		/* label is only initialized if consumer_label is set */
-- 
2.52.0.457.g6b5491de43-goog