[PATCHv6] gpio: Remove VLA from gpiolib

Message ID 20180517000027.26639-1-labbott@redhat.com
State New
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Series
  • [PATCHv6] gpio: Remove VLA from gpiolib
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Commit Message

Laura Abbott May 17, 2018, midnight
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.

Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v6: Introduce a config option for setting the fast path GPIOs because
there are too many combinations to make the arch default workable. I
went with a default of 512 in the Kconfig.

Also to other points: I don't think the warning should be triggerable
from userspace, it should only happen on probe. I also think only
memsetting half the array is more likely to be error prone. We can
change it if there is significant overhead.
---
 drivers/gpio/Kconfig          | 10 +++++
 drivers/gpio/gpiolib.c        | 76 +++++++++++++++++++++++++++--------
 drivers/gpio/gpiolib.h        |  2 +-
 include/linux/gpio/consumer.h | 10 +++--
 4 files changed, 76 insertions(+), 22 deletions(-)

Comments

Phil Reid May 17, 2018, 12:28 a.m. | #1
On 17/05/2018 08:00, Laura Abbott wrote:
> 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.
> 
> Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> v6: Introduce a config option for setting the fast path GPIOs because
> there are too many combinations to make the arch default workable. I
> went with a default of 512 in the Kconfig.
> 
> Also to other points: I don't think the warning should be triggerable
> from userspace, it should only happen on probe. I also think only
> memsetting half the array is more likely to be error prone. We can
> change it if there is significant overhead.
> ---
>   drivers/gpio/Kconfig          | 10 +++++
>   drivers/gpio/gpiolib.c        | 76 +++++++++++++++++++++++++++--------
>   drivers/gpio/gpiolib.h        |  2 +-
>   include/linux/gpio/consumer.h | 10 +++--
>   4 files changed, 76 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 68d812b38be7..2855b5c5c8ca 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -22,6 +22,16 @@ menuconfig GPIOLIB
>   
>   if GPIOLIB
>   
> +config GPIOLIB_FASTPATH_LIMIT
> +	int "Maximum number of GPIOs for fast path"
> +	default 512
> +	help
> +	   This adjusts the point at which certain APIs will switch from
> +	   using a statically allocated fixed size buffer to a dynamically
> +	   allocated buffer. This is a trade-off in stackspace vs. speed.
> +	   You shouldn't need to change this unless you really need to
> +	   optimize one of those two.
> +
>   config OF_GPIO
>   	def_bool y
>   	depends on OF
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index d66de67ef307..f7ce546796e0 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -61,6 +61,11 @@ static struct bus_type gpio_bus_type = {
>   	.name = "gpio",
>   };
>   
> +/*
> + * Number of GPIOs to use for the fast path in set array
> + */
> +#define FASTPATH_NGPIO CONFIG_GPIOLIB_FASTPATH_LIMIT
> +
>   /* gpio_lock prevents conflicts during gpio_desc[] table updates.
>    * While any GPIO is requested, its gpio_chip is not removable;
>    * each GPIO's "requested" flag serves as a lock and refcount.
> @@ -399,12 +404,11 @@ 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,
> +		return gpiod_set_array_value_complex(false,
>   					      true,
>   					      lh->numdescs,
>   					      lh->descs,
>   					      vals);
> -		return 0;
>   	}
>   	return -EINVAL;
>   }
> @@ -1192,6 +1196,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   		goto err_free_descs;
>   	}
>   
> +	if (chip->ngpio > FASTPATH_NGPIO)
> +		chip_warn(chip, "line cnt %d is greater than fast path cnt %d\n",
> +		chip->ngpio, FASTPATH_NGPIO);
> +
>   	gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
>   	if (!gdev->label) {
>   		status = -ENOMEM;
> @@ -2662,16 +2670,28 @@ 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 *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 {
> +			mask = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
> +					   sizeof(*mask),
> +					   can_sleep ? GFP_KERNEL : GFP_ATOMIC);
> +			if (!mask)
> +				return -ENOMEM;
> +			bits = mask + 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 +2702,11 @@ 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 (mask != fastpath)
> +				kfree(mask);
>   			return ret;
> +		}
>   
>   		for (j = first; j < i; j++) {
>   			const struct gpio_desc *desc = desc_array[j];
> @@ -2695,6 +2718,9 @@ 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 (mask != fastpath)
> +			kfree(mask);
>   	}
>   	return 0;
>   }
> @@ -2878,7 +2904,7 @@ 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 +2913,26 @@ 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 *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 {
> +			mask = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
> +					   sizeof(*mask),
> +					   can_sleep ? GFP_KERNEL : GFP_ATOMIC);
> +			if (!mask)
> +				return -ENOMEM;
> +			bits = mask + 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 (mask != fastpath)
> +			kfree(mask);
>   	}
> +	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)
> 
G'day Laura,

Looks good to me.

Reviewed-by: Phil Reid <preid@electromag.com.au>
Geert Uytterhoeven May 17, 2018, 7:58 a.m. | #2
Hi Laura,

On Thu, May 17, 2018 at 2:00 AM, Laura Abbott <labbott@redhat.com> wrote:
> 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.
>
> Reviewed-and-tested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Laura Abbott <labbott@redhat.com>

Thanks for your patch!

> Also to other points: I don't think the warning should be triggerable
> from userspace, it should only happen on probe. I also think only
> memsetting half the array is more likely to be error prone. We can
> change it if there is significant overhead.

With the default of 512, that's a memset of 128 bytes. Not so insignificant
on embedded 32 bit.

> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -22,6 +22,16 @@ menuconfig GPIOLIB
>
>  if GPIOLIB
>
> +config GPIOLIB_FASTPATH_LIMIT
> +       int "Maximum number of GPIOs for fast path"
> +       default 512

I think you need a range here.  Else someone will pick a too large value,
causing stack overflow.

512 (128 bytes for each recursion level) sounds like a safe maximum to me.

> +       help
> +          This adjusts the point at which certain APIs will switch from
> +          using a statically allocated fixed size buffer to a dynamically

The fast path doesn't use a statically allocated buffer (it cannot, due to
recursion), but a buffer on the stack. I think you need to make that very
clear in the help text, as this has the potential of causing random crashes.

> +          allocated buffer. This is a trade-off in stackspace vs. speed.
> +          You shouldn't need to change this unless you really need to
> +          optimize one of those two.

> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c

> @@ -1192,6 +1196,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>                 goto err_free_descs;
>         }
>
> +       if (chip->ngpio > FASTPATH_NGPIO)
> +               chip_warn(chip, "line cnt %d is greater than fast path cnt %d\n",

%u (twice)

> +               chip->ngpio, FASTPATH_NGPIO);
> +
>         gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
>         if (!gdev->label) {
>                 status = -ENOMEM;
> @@ -2662,16 +2670,28 @@ 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 *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 {
> +                       mask = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
> +                                          sizeof(*mask),
> +                                          can_sleep ? GFP_KERNEL : GFP_ATOMIC);
> +                       if (!mask)
> +                               return -ENOMEM;
> +                       bits = mask + BITS_TO_LONGS(chip->ngpio);
> +               }

The assignment to bits could be made common, and moved out of the if/else.

Likewise for the memset, which means you would usually clear a single word
again, instead of 128 bytes (or more).

Gr{oetje,eeting}s,

                        Geert

Patch

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 68d812b38be7..2855b5c5c8ca 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -22,6 +22,16 @@  menuconfig GPIOLIB
 
 if GPIOLIB
 
+config GPIOLIB_FASTPATH_LIMIT
+	int "Maximum number of GPIOs for fast path"
+	default 512
+	help
+	   This adjusts the point at which certain APIs will switch from
+	   using a statically allocated fixed size buffer to a dynamically
+	   allocated buffer. This is a trade-off in stackspace vs. speed.
+	   You shouldn't need to change this unless you really need to
+	   optimize one of those two.
+
 config OF_GPIO
 	def_bool y
 	depends on OF
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d66de67ef307..f7ce546796e0 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -61,6 +61,11 @@  static struct bus_type gpio_bus_type = {
 	.name = "gpio",
 };
 
+/*
+ * Number of GPIOs to use for the fast path in set array
+ */
+#define FASTPATH_NGPIO CONFIG_GPIOLIB_FASTPATH_LIMIT
+
 /* gpio_lock prevents conflicts during gpio_desc[] table updates.
  * While any GPIO is requested, its gpio_chip is not removable;
  * each GPIO's "requested" flag serves as a lock and refcount.
@@ -399,12 +404,11 @@  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,
+		return gpiod_set_array_value_complex(false,
 					      true,
 					      lh->numdescs,
 					      lh->descs,
 					      vals);
-		return 0;
 	}
 	return -EINVAL;
 }
@@ -1192,6 +1196,10 @@  int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 		goto err_free_descs;
 	}
 
+	if (chip->ngpio > FASTPATH_NGPIO)
+		chip_warn(chip, "line cnt %d is greater than fast path cnt %d\n",
+		chip->ngpio, FASTPATH_NGPIO);
+
 	gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
 	if (!gdev->label) {
 		status = -ENOMEM;
@@ -2662,16 +2670,28 @@  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 *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 {
+			mask = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
+					   sizeof(*mask),
+					   can_sleep ? GFP_KERNEL : GFP_ATOMIC);
+			if (!mask)
+				return -ENOMEM;
+			bits = mask + 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 +2702,11 @@  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 (mask != fastpath)
+				kfree(mask);
 			return ret;
+		}
 
 		for (j = first; j < i; j++) {
 			const struct gpio_desc *desc = desc_array[j];
@@ -2695,6 +2718,9 @@  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 (mask != fastpath)
+			kfree(mask);
 	}
 	return 0;
 }
@@ -2878,7 +2904,7 @@  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 +2913,26 @@  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 *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 {
+			mask = kcalloc(2 * BITS_TO_LONGS(chip->ngpio),
+					   sizeof(*mask),
+					   can_sleep ? GFP_KERNEL : GFP_ATOMIC);
+			if (!mask)
+				return -ENOMEM;
+			bits = mask + 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 (mask != fastpath)
+			kfree(mask);
 	}
+	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)