gpio: Remove VLA from gpiolib
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-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Phil Reid <preid@electromag.com.au>
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>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d1171db6..487edf1 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.
@@ -453,12 +458,11 @@ 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;
}
@@ -1281,6 +1285,10 @@ 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 %u is greater than fast path cnt %u\n",
+ chip->ngpio, FASTPATH_NGPIO);
+
gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
if (!gdev->label) {
status = -ENOMEM;
@@ -2758,16 +2766,28 @@ 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)) {
+ mask = fastpath;
+ } else {
+ mask = kmalloc_array(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);
+ bitmap_zero(mask, 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);
@@ -2778,8 +2798,11 @@ 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];
@@ -2791,6 +2814,9 @@ 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;
}
@@ -2974,7 +3000,7 @@ 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)
@@ -2983,14 +3009,26 @@ 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)) {
+ mask = fastpath;
+ } else {
+ mask = kmalloc_array(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);
+ bitmap_zero(mask, 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);
@@ -3021,7 +3059,11 @@ 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;
}
/**
@@ -3096,13 +3138,13 @@ 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);
@@ -3422,14 +3464,14 @@ 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);