linux-kernel - Re: [PATCH] gpio: mockup: use simple_read_from

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Date:   Thu, 28 Mar 2019 14:42:25 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Mukesh Ojha <mojha@...eaurora.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] gpio: mockup: use simple_read_from_buffer() in debugfs
 read callback

czw., 28 mar 2019 o 14:11 Mukesh Ojha <mojha@...eaurora.org> napisał(a):
>
>
> On 3/28/2019 4:30 PM, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> >
> > Calling read() for a single byte read will return 2 currently. Use
> > simple_read_from_buffer() which correctly handles all sizes.
> >
> > Fixes: 2a9e27408e12 ("gpio: mockup: rework debugfs interface")
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > ---
> >   drivers/gpio/gpio-mockup.c | 7 +------
> >   1 file changed, 1 insertion(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> > index 74ba8b1d71d8..859585dce5c9 100644
> > --- a/drivers/gpio/gpio-mockup.c
> > +++ b/drivers/gpio/gpio-mockup.c
> > @@ -219,12 +219,7 @@ static ssize_t gpio_mockup_debugfs_read(struct file *file,
> >       val = gpio_mockup_get(gc, priv->offset);
> >       cnt = snprintf(buf, sizeof(buf), "%d\n", val);
>
>
> why \n is inserted in the buf..
>

Because this is how all the attributes work - you read the value + '\n'.

> rv variable is unused now.
>
> >
> > -     rv = copy_to_user(usr_buf, buf, cnt);
> > -     if (rv)
> > -             return rv;
> > -
> > -     *ppos += cnt;
> > -     return cnt;
> > +     return simple_read_from_buffer(usr_buf, size, ppos, buf, cnt);
>
>
>
> Looks good to me.
> Remove the unused variable.
>

Thanks, removed that and a stray newline.

Bart

> Reviewed-by: Mukesh Ojha <mojha@...eaurora.org>
>
> -Mukesh
>
> >   }
> >
> >   static ssize_t gpio_mockup_debugfs_write(struct file *file,