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>
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@ -22,6 +22,18 @@ menuconfig GPIOLIB
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if GPIOLIB
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config GPIOLIB_FASTPATH_LIMIT
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int "Maximum number of GPIOs for fast path"
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range 32 512
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default 512
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help
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This adjusts the point at which certain APIs will switch from
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using a stack allocated buffer to a dynamically allocated buffer.
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You shouldn't need to change this unless you really need to
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optimize either stack space or performance. Change this carefully
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since setting an incorrect value could cause stack corruption.
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config OF_GPIO
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def_bool y
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depends on OF
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@ -61,6 +61,11 @@ static struct bus_type gpio_bus_type = {
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.name = "gpio",
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};
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/*
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* Number of GPIOs to use for the fast path in set array
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*/
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#define FASTPATH_NGPIO CONFIG_GPIOLIB_FASTPATH_LIMIT
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/* gpio_lock prevents conflicts during gpio_desc[] table updates.
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* While any GPIO is requested, its gpio_chip is not removable;
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* each GPIO's "requested" flag serves as a lock and refcount.
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@ -453,12 +458,11 @@ static long linehandle_ioctl(struct file *filep, unsigned int cmd,
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vals[i] = !!ghd.values[i];
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/* Reuse the array setting function */
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gpiod_set_array_value_complex(false,
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return gpiod_set_array_value_complex(false,
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true,
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lh->numdescs,
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lh->descs,
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vals);
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return 0;
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}
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return -EINVAL;
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}
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@ -1281,6 +1285,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
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goto err_free_descs;
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}
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if (chip->ngpio > FASTPATH_NGPIO)
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chip_warn(chip, "line cnt %u is greater than fast path cnt %u\n",
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chip->ngpio, FASTPATH_NGPIO);
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gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
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if (!gdev->label) {
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status = -ENOMEM;
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@ -2758,16 +2766,28 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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while (i < array_size) {
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struct gpio_chip *chip = desc_array[i]->gdev->chip;
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unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
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unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
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unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)];
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unsigned long *mask, *bits;
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int first, j, ret;
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if (likely(chip->ngpio <= FASTPATH_NGPIO)) {
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mask = fastpath;
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} else {
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mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio),
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sizeof(*mask),
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can_sleep ? GFP_KERNEL : GFP_ATOMIC);
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if (!mask)
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return -ENOMEM;
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}
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bits = mask + BITS_TO_LONGS(chip->ngpio);
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bitmap_zero(mask, chip->ngpio);
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if (!can_sleep)
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WARN_ON(chip->can_sleep);
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/* collect all inputs belonging to the same chip */
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first = i;
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memset(mask, 0, sizeof(mask));
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do {
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const struct gpio_desc *desc = desc_array[i];
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int hwgpio = gpio_chip_hwgpio(desc);
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@ -2778,8 +2798,11 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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(desc_array[i]->gdev->chip == chip));
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ret = gpio_chip_get_multiple(chip, mask, bits);
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if (ret)
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if (ret) {
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if (mask != fastpath)
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kfree(mask);
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return ret;
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}
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for (j = first; j < i; j++) {
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const struct gpio_desc *desc = desc_array[j];
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@ -2791,6 +2814,9 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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value_array[j] = value;
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trace_gpio_value(desc_to_gpio(desc), 1, value);
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}
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if (mask != fastpath)
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kfree(mask);
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}
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return 0;
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}
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@ -2974,7 +3000,7 @@ static void gpio_chip_set_multiple(struct gpio_chip *chip,
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}
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}
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void gpiod_set_array_value_complex(bool raw, bool can_sleep,
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int gpiod_set_array_value_complex(bool raw, bool can_sleep,
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unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array)
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@ -2983,14 +3009,26 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep,
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while (i < array_size) {
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struct gpio_chip *chip = desc_array[i]->gdev->chip;
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unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
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unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
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unsigned long fastpath[2 * BITS_TO_LONGS(FASTPATH_NGPIO)];
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unsigned long *mask, *bits;
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int count = 0;
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if (likely(chip->ngpio <= FASTPATH_NGPIO)) {
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mask = fastpath;
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} else {
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mask = kmalloc_array(2 * BITS_TO_LONGS(chip->ngpio),
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sizeof(*mask),
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can_sleep ? GFP_KERNEL : GFP_ATOMIC);
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if (!mask)
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return -ENOMEM;
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}
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bits = mask + BITS_TO_LONGS(chip->ngpio);
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bitmap_zero(mask, chip->ngpio);
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if (!can_sleep)
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WARN_ON(chip->can_sleep);
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memset(mask, 0, sizeof(mask));
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do {
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struct gpio_desc *desc = desc_array[i];
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int hwgpio = gpio_chip_hwgpio(desc);
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@ -3021,7 +3059,11 @@ void gpiod_set_array_value_complex(bool raw, bool can_sleep,
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/* push collected bits to outputs */
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if (count != 0)
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gpio_chip_set_multiple(chip, mask, bits);
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if (mask != fastpath)
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kfree(mask);
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}
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return 0;
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}
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/**
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@ -3096,13 +3138,13 @@ EXPORT_SYMBOL_GPL(gpiod_set_value);
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* This function should be called from contexts where we cannot sleep, and will
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* complain if the GPIO chip functions potentially sleep.
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*/
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void gpiod_set_raw_array_value(unsigned int array_size,
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int gpiod_set_raw_array_value(unsigned int array_size,
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struct gpio_desc **desc_array, int *value_array)
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{
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if (!desc_array)
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return;
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gpiod_set_array_value_complex(true, false, array_size, desc_array,
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value_array);
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return -EINVAL;
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return gpiod_set_array_value_complex(true, false, array_size,
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desc_array, value_array);
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}
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EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value);
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@ -3422,14 +3464,14 @@ EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
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*
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* This function is to be called from contexts that can sleep.
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*/
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void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array)
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{
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might_sleep_if(extra_checks);
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if (!desc_array)
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return;
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gpiod_set_array_value_complex(true, true, array_size, desc_array,
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return -EINVAL;
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return gpiod_set_array_value_complex(true, true, array_size, desc_array,
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value_array);
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}
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EXPORT_SYMBOL_GPL(gpiod_set_raw_array_value_cansleep);
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@ -188,7 +188,7 @@ int gpiod_get_array_value_complex(bool raw, bool can_sleep,
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unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array);
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void gpiod_set_array_value_complex(bool raw, bool can_sleep,
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int gpiod_set_array_value_complex(bool raw, bool can_sleep,
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unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array);
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@ -116,7 +116,7 @@ int gpiod_get_raw_array_value(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array);
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void gpiod_set_raw_value(struct gpio_desc *desc, int value);
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void gpiod_set_raw_array_value(unsigned int array_size,
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int gpiod_set_raw_array_value(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array);
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struct gpio_desc **desc_array,
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int *value_array);
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void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value);
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void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array);
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/* GPIO can never have been requested */
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WARN_ON(1);
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}
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static inline void gpiod_set_raw_array_value(unsigned int array_size,
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static inline int gpiod_set_raw_array_value(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array)
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{
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/* GPIO can never have been requested */
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WARN_ON(1);
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return 0;
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}
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static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc)
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/* GPIO can never have been requested */
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WARN_ON(1);
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}
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static inline void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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static inline int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
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struct gpio_desc **desc_array,
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int *value_array)
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{
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/* GPIO can never have been requested */
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WARN_ON(1);
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return 0;
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}
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static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
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