linux-kernel - Re: [PATCH] video/via: Convert to kstrtou8_from

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Date:	Mon, 16 Apr 2012 19:36:27 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Peter Huewe <peterhuewe@....de>
Cc:	Florian Tobias Schandinat <FlorianSchandinat@....de>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] video/via: Convert to kstrtou8_from_user

On Sun, Apr 15, 2012 at 2:24 AM, Peter Huewe <peterhuewe@....de> wrote:
> This patch replaces the code for getting an number from a
> userspace buffer by a simple call to kstrou8_from_user.
> This makes it easier to read and less error prone.

Initialization with 0 is not necessary then.
Also "count < 1" check could be dropped, since empty string will fail
with EINVAL.
Otherwise OK.

> --- a/drivers/video/via/viafbdev.c
> +++ b/drivers/video/via/viafbdev.c
> @@ -1276,17 +1276,14 @@ static int viafb_dfph_proc_open(struct inode *inode, struct file *file)
>  static ssize_t viafb_dfph_proc_write(struct file *file,
>        const char __user *buffer, size_t count, loff_t *pos)
>  {
> -       char buf[20];
> +       int err;
>        u8 reg_val = 0;
> -       unsigned long length;
>        if (count < 1)
>                return -EINVAL;
> -       length = count > 20 ? 20 : count;
> -       if (copy_from_user(&buf[0], buffer, length))
> -               return -EFAULT;
> -       buf[length - 1] = '\0'; /*Ensure end string */
> -       if (kstrtou8(buf, 0, &reg_val) < 0)
> -               return -EINVAL;
> +       err = kstrtou8_from_user(buffer, count, 0, &reg_val);
> +       if (err)
> +               return err;
> +
>        viafb_write_reg_mask(CR97, VIACR, reg_val, 0x0f);
>        return count;
>  }
> @@ -1316,17 +1313,14 @@ static int viafb_dfpl_proc_open(struct inode *inode, struct file *file)
>  static ssize_t viafb_dfpl_proc_write(struct file *file,
>        const char __user *buffer, size_t count, loff_t *pos)
>  {
> -       char buf[20];
> +       int err;
>        u8 reg_val = 0;
> -       unsigned long length;
>        if (count < 1)
>                return -EINVAL;
> -       length = count > 20 ? 20 : count;
> -       if (copy_from_user(&buf[0], buffer, length))
> -               return -EFAULT;
> -       buf[length - 1] = '\0'; /*Ensure end string */
> -       if (kstrtou8(buf, 0, &reg_val) < 0)
> -               return -EINVAL;
> +       err = kstrtou8_from_user(buffer, count, 0, &reg_val);
> +       if (err)
> +               return err;
> +
>        viafb_write_reg_mask(CR99, VIACR, reg_val, 0x0f);
>        return count;
>  }
> --
> 1.7.3.4
>
> --
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