[PATCHv3] gpio: Remove VLA from gpiolib
From: Laura Abbott
Date: Wed Mar 28 2018 - 14:18:26 EST
The new challenge is to remove VLAs from the kernel
(see https://lkml.org/lkml/2018/3/7/621) to eventually
turn on -Wvla.
Using a kmalloc array is the easy way to fix this but kmalloc is still
more expensive than stack allocation. Introduce a fast path with a
fixed size stack array to cover most chip with gpios below some fixed
amount. The slow path dynamically allocates an array to cover those
chips with a large number of gpios.
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
---
v3: Split out from the series since patches have been picked up
independently. Fold in patch from Lukas Wunner to introduce slow/fast
paths. I took his suggestions to go with 384 as the maximum number of
gpios. Also fixed one 0-day bot issue where I forgot to change the
return type.
---
drivers/gpio/gpiolib.c | 74 +++++++++++++++++++++++++++++++++----------
drivers/gpio/gpiolib.h | 2 +-
include/linux/gpio/consumer.h | 10 +++---
3 files changed, 65 insertions(+), 21 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d66de67ef307..e3ca9e31bcbc 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -390,6 +390,7 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd,
return 0;
} else if (cmd == GPIOHANDLE_SET_LINE_VALUES_IOCTL) {
+ int ret;
/* TODO: check if descriptors are really output */
if (copy_from_user(&ghd, ip, sizeof(ghd)))
return -EFAULT;
@@ -399,11 +400,14 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd,
vals[i] = !!ghd.values[i];
/* Reuse the array setting function */
- gpiod_set_array_value_complex(false,
+ ret = gpiod_set_array_value_complex(false,
true,
lh->numdescs,
lh->descs,
vals);
+ if (ret)
+ return ret;
+
return 0;
}
return -EINVAL;
@@ -2653,6 +2657,8 @@ static int gpio_chip_get_multiple(struct gpio_chip *chip,
return -EIO;
}
+#define FASTPATH_NGPIO 384
+
int gpiod_get_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
@@ -2662,16 +2668,29 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
while (i < array_size) {
struct gpio_chip *chip = desc_array[i]->gdev->chip;
- unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
- unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
+ unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)];
+ unsigned long *slowpath = NULL, *mask, *bits;
int first, j, ret;
+ if (likely(chip->ngpio <= FASTPATH_NGPIO)) {
+ memset(fastpath, 0, sizeof(fastpath));
+ mask = fastpath;
+ bits = fastpath + BITS_TO_LONGS(FASTPATH_NGPIO);
+ } else {
+ slowpath = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
+ sizeof(*slowpath),
+ can_sleep ? GFP_KERNEL : GFP_ATOMIC);
+ if (!slowpath)
+ return -ENOMEM;
+ mask = slowpath;
+ bits = slowpath + BITS_TO_LONGS(chip->ngpio);
+ }
+
if (!can_sleep)
WARN_ON(chip->can_sleep);
/* collect all inputs belonging to the same chip */
first = i;
- memset(mask, 0, sizeof(mask));
do {
const struct gpio_desc *desc = desc_array[i];
int hwgpio = gpio_chip_hwgpio(desc);
@@ -2682,8 +2701,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
(desc_array[i]->gdev->chip == chip));
ret = gpio_chip_get_multiple(chip, mask, bits);
- if (ret)
+ if (ret) {
+ if (slowpath)
+ kfree(slowpath);
return ret;
+ }
for (j = first; j < i; j++) {
const struct gpio_desc *desc = desc_array[j];
@@ -2695,6 +2717,9 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
value_array[j] = value;
trace_gpio_value(desc_to_gpio(desc), 1, value);
}
+
+ if (slowpath)
+ kfree(slowpath);
}
return 0;
}
@@ -2878,7 +2903,7 @@ static void gpio_chip_set_multiple(struct gpio_chip *chip,
}
}
-void gpiod_set_array_value_complex(bool raw, bool can_sleep,
+int gpiod_set_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
@@ -2887,14 +2912,27 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep,
while (i < array_size) {
struct gpio_chip *chip = desc_array[i]->gdev->chip;
- unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
- unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
+ unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)];
+ unsigned long *slowpath = NULL, *mask, *bits;
int count = 0;
+ if (likely(chip->ngpio <= FASTPATH_NGPIO)) {
+ memset(fastpath, 0, sizeof(fastpath));
+ mask = fastpath;
+ bits = fastpath + BITS_TO_LONGS(FASTPATH_NGPIO);
+ } else {
+ slowpath = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
+ sizeof(*slowpath),
+ can_sleep ? GFP_KERNEL : GFP_ATOMIC);
+ if (!slowpath)
+ return -ENOMEM;
+ mask = slowpath;
+ bits = slowpath + BITS_TO_LONGS(chip->ngpio);
+ }
+
if (!can_sleep)
WARN_ON(chip->can_sleep);
- memset(mask, 0, sizeof(mask));
do {
struct gpio_desc *desc = desc_array[i];
int hwgpio = gpio_chip_hwgpio(desc);
@@ -2925,7 +2963,11 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep,
/* push collected bits to outputs */
if (count != 0)
gpio_chip_set_multiple(chip, mask, bits);
+
+ if (slowpath)
+ kfree(slowpath);
}
+ return 0;
}
/**
@@ -3000,13 +3042,13 @@ EXPORT_SYMBOL_GPL(gpiod_set_value);
* This function should be called from contexts where we cannot sleep, and will
* complain if the GPIO chip functions potentially sleep.
*/
-void gpiod_set_raw_array_value(unsigned int array_size,
+int gpiod_set_raw_array_value(unsigned int array_size,
struct gpio_desc **desc_array, int *value_array)
{
if (!desc_array)
- return;
- gpiod_set_array_value_complex(true, false, array_size, desc_array,
- value_array);
+ return -EINVAL;
+ return gpiod_set_array_value_complex(true, false, array_size,
+ desc_array, value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value);
@@ -3326,14 +3368,14 @@ EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
*
* This function is to be called from contexts that can sleep.
*/
-void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
+int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
{
might_sleep_if(extra_checks);
if (!desc_array)
- return;
- gpiod_set_array_value_complex(true, true, array_size, desc_array,
+ return -EINVAL;
+ return gpiod_set_array_value_complex(true, true, array_size, desc_array,
value_array);
}
EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value_cansleep);
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index b17ec6795c81..b64813e3876e 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -188,7 +188,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
-void gpiod_set_array_value_complex(bool raw, bool can_sleep,
+int gpiod_set_array_value_complex(bool raw, bool can_sleep,
unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index dbd065963296..243112c7fa7d 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -116,7 +116,7 @@ int gpiod_get_raw_array_value(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
void gpiod_set_raw_value(struct gpio_desc *desc, int value);
-void gpiod_set_raw_array_value(unsigned int array_size,
+int gpiod_set_raw_array_value(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
@@ -134,7 +134,7 @@ int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value);
-void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
+int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
@@ -369,12 +369,13 @@ static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value)
/* GPIO can never have been requested */
WARN_ON(1);
}
-static inline void gpiod_set_raw_array_value(unsigned int array_size,
+static inline int gpiod_set_raw_array_value(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
{
/* GPIO can never have been requested */
WARN_ON(1);
+ return 0;
}
static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc)
@@ -423,12 +424,13 @@ static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc,
/* GPIO can never have been requested */
WARN_ON(1);
}
-static inline void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
+static inline int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
{
/* GPIO can never have been requested */
WARN_ON(1);
+ return 0;
}
static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
--
2.14.3