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Message-ID: <20250207140640.57664-1-brgl@bgdev.pl>
Date: Fri, 7 Feb 2025 15:06:40 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: linux-gpio@...r.kernel.org,
linux-kernel@...r.kernel.org,
David Lechner <dlechner@...libre.com>,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
stable@...r.kernel.org
Subject: [PATCH] gpiolib: protect gpio_chip with SRCU in array_info paths in multi get/set
From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
During the locking rework in GPIOLIB, we omitted one important use-case,
namely: setting and getting values for GPIO descriptor arrays with
array_info present.
This patch does two things: first it makes struct gpio_array store the
address of the underlying GPIO device and not chip. Next: it protects
the chip with SRCU from removal in gpiod_get_array_value_complex() and
gpiod_set_array_value_complex().
Cc: stable@...r.kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
David Lechner's series made me realize that we don't use SRCU to protect
the GPIO chip in case where array_info is available in multiple get/set
routines. This addresses it. The changes here could potentially be split
into two separate commits but I want to easily backport it and it works
together as well.
drivers/gpio/gpiolib.c | 48 +++++++++++++++++++++++++++++-------------
drivers/gpio/gpiolib.h | 4 ++--
2 files changed, 35 insertions(+), 17 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 679ed764cb14..6e630680be52 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3129,6 +3129,8 @@ static int gpiod_get_raw_value_commit(const struct gpio_desc *desc)
static int gpio_chip_get_multiple(struct gpio_chip *gc,
unsigned long *mask, unsigned long *bits)
{
+ lockdep_assert_held(&gc->gpiodev->srcu);
+
if (gc->get_multiple)
return gc->get_multiple(gc, mask, bits);
if (gc->get) {
@@ -3159,6 +3161,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
struct gpio_array *array_info,
unsigned long *value_bitmap)
{
+ struct gpio_chip *gc;
int ret, i = 0;
/*
@@ -3170,10 +3173,15 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
array_size <= array_info->size &&
(void *)array_info == desc_array + array_info->size) {
if (!can_sleep)
- WARN_ON(array_info->chip->can_sleep);
+ WARN_ON(array_info->gdev->can_sleep);
- ret = gpio_chip_get_multiple(array_info->chip,
- array_info->get_mask,
+ guard(srcu)(&array_info->gdev->srcu);
+ gc = srcu_dereference(array_info->gdev->chip,
+ &array_info->gdev->srcu);
+ if (!gc)
+ return -ENODEV;
+
+ ret = gpio_chip_get_multiple(gc, array_info->get_mask,
value_bitmap);
if (ret)
return ret;
@@ -3454,6 +3462,8 @@ static void gpiod_set_raw_value_commit(struct gpio_desc *desc, bool value)
static void gpio_chip_set_multiple(struct gpio_chip *gc,
unsigned long *mask, unsigned long *bits)
{
+ lockdep_assert_held(&gc->gpiodev->srcu);
+
if (gc->set_multiple) {
gc->set_multiple(gc, mask, bits);
} else {
@@ -3471,6 +3481,7 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
struct gpio_array *array_info,
unsigned long *value_bitmap)
{
+ struct gpio_chip *gc;
int i = 0;
/*
@@ -3482,14 +3493,19 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
array_size <= array_info->size &&
(void *)array_info == desc_array + array_info->size) {
if (!can_sleep)
- WARN_ON(array_info->chip->can_sleep);
+ WARN_ON(array_info->gdev->can_sleep);
+
+ guard(srcu)(&array_info->gdev->srcu);
+ gc = srcu_dereference(array_info->gdev->chip,
+ &array_info->gdev->srcu);
+ if (!gc)
+ return -ENODEV;
if (!raw && !bitmap_empty(array_info->invert_mask, array_size))
bitmap_xor(value_bitmap, value_bitmap,
array_info->invert_mask, array_size);
- gpio_chip_set_multiple(array_info->chip, array_info->set_mask,
- value_bitmap);
+ gpio_chip_set_multiple(gc, array_info->set_mask, value_bitmap);
i = find_first_zero_bit(array_info->set_mask, array_size);
if (i == array_size)
@@ -4751,8 +4767,8 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
{
struct gpio_desc *desc;
struct gpio_descs *descs;
+ struct gpio_device *gdev;
struct gpio_array *array_info = NULL;
- struct gpio_chip *gc;
int count, bitmap_size;
size_t descs_size;
@@ -4774,7 +4790,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
descs->desc[descs->ndescs] = desc;
- gc = gpiod_to_chip(desc);
+ gdev = gpiod_to_gpio_device(desc);
/*
* If pin hardware number of array member 0 is also 0, select
* its chip as a candidate for fast bitmap processing path.
@@ -4782,8 +4798,8 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
if (descs->ndescs == 0 && gpio_chip_hwgpio(desc) == 0) {
struct gpio_descs *array;
- bitmap_size = BITS_TO_LONGS(gc->ngpio > count ?
- gc->ngpio : count);
+ bitmap_size = BITS_TO_LONGS(gdev->ngpio > count ?
+ gdev->ngpio : count);
array = krealloc(descs, descs_size +
struct_size(array_info, invert_mask, 3 * bitmap_size),
@@ -4803,7 +4819,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
array_info->desc = descs->desc;
array_info->size = count;
- array_info->chip = gc;
+ array_info->gdev = gdev;
bitmap_set(array_info->get_mask, descs->ndescs,
count - descs->ndescs);
bitmap_set(array_info->set_mask, descs->ndescs,
@@ -4816,7 +4832,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
continue;
/* Unmark array members which don't belong to the 'fast' chip */
- if (array_info->chip != gc) {
+ if (array_info->gdev != gdev) {
__clear_bit(descs->ndescs, array_info->get_mask);
__clear_bit(descs->ndescs, array_info->set_mask);
}
@@ -4840,8 +4856,10 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
}
} else {
/* Exclude open drain or open source from fast output */
- if (gpiochip_line_is_open_drain(gc, descs->ndescs) ||
- gpiochip_line_is_open_source(gc, descs->ndescs))
+ if (gpiochip_line_is_open_drain(gdev->chip,
+ descs->ndescs) ||
+ gpiochip_line_is_open_source(gdev->chip,
+ descs->ndescs))
__clear_bit(descs->ndescs,
array_info->set_mask);
/* Identify 'fast' pins which require invertion */
@@ -4853,7 +4871,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
if (array_info)
dev_dbg(dev,
"GPIO array info: chip=%s, size=%d, get_mask=%lx, set_mask=%lx, invert_mask=%lx\n",
- array_info->chip->label, array_info->size,
+ array_info->gdev->label, array_info->size,
*array_info->get_mask, *array_info->set_mask,
*array_info->invert_mask);
return descs;
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 83690f72f7e5..147156ec502b 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -114,7 +114,7 @@ extern const char *const gpio_suffixes[];
*
* @desc: Array of pointers to the GPIO descriptors
* @size: Number of elements in desc
- * @chip: Parent GPIO chip
+ * @gdev: Parent GPIO device
* @get_mask: Get mask used in fastpath
* @set_mask: Set mask used in fastpath
* @invert_mask: Invert mask used in fastpath
@@ -126,7 +126,7 @@ extern const char *const gpio_suffixes[];
struct gpio_array {
struct gpio_desc **desc;
unsigned int size;
- struct gpio_chip *chip;
+ struct gpio_device *gdev;
unsigned long *get_mask;
unsigned long *set_mask;
unsigned long invert_mask[];
--
2.45.2
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