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authorChristophe Leroy <christophe.leroy@c-s.fr>2017-12-18 13:08:33 +0300
committerLinus Walleij <linus.walleij@linaro.org>2017-12-20 12:34:01 +0300
commit7a94b88cb7087aa3184161bedccfea25e5502c62 (patch)
tree834dd94fd037c9b6edb3ba890e38df1af6cb77e1 /drivers/gpio/gpiolib-sysfs.c
parent9295c01253b4eda5dc0b5a5b2e0fd321fe57010c (diff)
downloadlinux-7a94b88cb7087aa3184161bedccfea25e5502c62.tar.xz
gpio: sysfs: don't use sprintf() for 'value' attribute
A bench with 'perf record' shows that most of time spent in value_show() is spent in sprintf() --42.41%--sysfs_kf_read | |--39.73%--dev_attr_show | | | |--38.23%--value_show | | | | | |--29.22%--sprintf | | | | | |--2.94%--gpiod_get_value_cansleep | | | value_show() only returns "0\n" or "1\n", therefore the use of sprintf() can be avoided With this patch we get the following result with 'perf record' --13.89%--sysfs_kf_read | |--10.72%--dev_attr_show | | | |--9.44%--value_show | | | | | |--4.61%--gpiod_get_value_cansleep Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/gpio/gpiolib-sysfs.c')
-rw-r--r--drivers/gpio/gpiolib-sysfs.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index ef34b8f56bd1..ad7173df72eb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -110,7 +110,9 @@ static ssize_t value_show(struct device *dev,
if (status < 0)
goto err;
- status = sprintf(buf, "%d\n", status);
+ buf[0] = '0' + status;
+ buf[1] = '\n';
+ status = 2;
err:
mutex_unlock(&data->mutex);