gpio: sysfs: avoid using kstrtol() in 'value' attribute write
A 'perf record' on an app continuously writing in the 'value' attribute show that most of the time is spent in kstrtol() --17.99%--value_store | |--10.17%--kstrtoint | | | |--8.82%--kstrtoll | |--2.50%--gpiod_set_value_cansleep | |--1.82%--u16_gpio_set | |--1.46%--value_store The normal case is to write 0 or 1 in the attribute, therefore this patch avoids the call to kstrtol() in the most common cases Then 'perf record' shows --7.21%--value_store | |--2.69%--u16_gpio_set | |--1.47%--value_store | |--1.08%--gpiod_set_value_cansleep | |--0.60%--mutex_lock | --0.58%--mutex_unlock Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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@ -8,6 +8,7 @@
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#include <linux/interrupt.h>
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#include <linux/kdev_t.h>
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#include <linux/slab.h>
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#include <linux/ctype.h>
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#include "gpiolib.h"
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@ -124,7 +125,7 @@ static ssize_t value_store(struct device *dev,
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{
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struct gpiod_data *data = dev_get_drvdata(dev);
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struct gpio_desc *desc = data->desc;
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ssize_t status;
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ssize_t status = 0;
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mutex_lock(&data->mutex);
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@ -133,7 +134,11 @@ static ssize_t value_store(struct device *dev,
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} else {
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long value;
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status = kstrtol(buf, 0, &value);
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if (size <= 2 && isdigit(buf[0]) &&
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(size == 1 || buf[1] == '\n'))
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value = buf[0] - '0';
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else
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status = kstrtol(buf, 0, &value);
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if (status == 0) {
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gpiod_set_value_cansleep(desc, value);
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status = size;
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