gpio: mockup: fix debugfs read

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 <bgolaszewski@baylibre.com>

diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
index 154d959..74ba8b1 100644 (file)
--- 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,