From: Bartosz Golaszewski <[email protected]>
The debugfs read callback must advance ppos or users using read() on
the file descriptor will never get the EOL. This wasn't spotted before
as I was using busybox cat for testing which uses sendfile() internally
and only noticed it now when switched to cat from coreutils.
Fixes: 2a9e27408e12 ("gpio: mockup: rework debugfs interface")
Signed-off-by: Bartosz Golaszewski <[email protected]>
---
drivers/gpio/gpio-mockup.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
index 154d959e8993..74ba8b1d71d8 100644
--- a/drivers/gpio/gpio-mockup.c
+++ b/drivers/gpio/gpio-mockup.c
@@ -204,8 +204,9 @@ static ssize_t gpio_mockup_debugfs_read(struct file *file,
struct gpio_mockup_chip *chip;
struct seq_file *sfile;
struct gpio_chip *gc;
+ int val, rv, cnt;
char buf[3];
- int val, rv;
+
if (*ppos != 0)
return 0;
@@ -216,13 +217,14 @@ static ssize_t gpio_mockup_debugfs_read(struct file *file,
gc = &chip->gc;
val = gpio_mockup_get(gc, priv->offset);
- snprintf(buf, sizeof(buf), "%d\n", val);
+ cnt = snprintf(buf, sizeof(buf), "%d\n", val);
- rv = copy_to_user(usr_buf, buf, sizeof(buf));
+ rv = copy_to_user(usr_buf, buf, cnt);
if (rv)
return rv;
- return sizeof(buf) - 1;
+ *ppos += cnt;
+ return cnt;
}
static ssize_t gpio_mockup_debugfs_write(struct file *file,
--
2.20.1
