From 1efba35afae43094d3f26093f5f1ab8a46686a6f Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Mon, 18 Dec 2017 11:08:35 +0100 Subject: [PATCH] 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 Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib-sysfs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c index ad7173df72eb..3dbaf489a8a5 100644 --- a/drivers/gpio/gpiolib-sysfs.c +++ b/drivers/gpio/gpiolib-sysfs.c @@ -8,6 +8,7 @@ #include #include #include +#include #include "gpiolib.h" @@ -124,7 +125,7 @@ static ssize_t value_store(struct device *dev, { struct gpiod_data *data = dev_get_drvdata(dev); struct gpio_desc *desc = data->desc; - ssize_t status; + ssize_t status = 0; mutex_lock(&data->mutex); @@ -133,7 +134,11 @@ static ssize_t value_store(struct device *dev, } else { long value; - status = kstrtol(buf, 0, &value); + if (size <= 2 && isdigit(buf[0]) && + (size == 1 || buf[1] == '\n')) + value = buf[0] - '0'; + else + status = kstrtol(buf, 0, &value); if (status == 0) { gpiod_set_value_cansleep(desc, value); status = size;