Re: [RFC PATCH v2 3/4] ppdev: add compat ioctl

[John Stultz <john.stultz@linaro.org>]

On Mon, Jun 29, 2015 at 7:23 AM, Bamvor Zhang Jian
<bamvor.zhangjian@linaro.org> wrote:
> Add compat ioctl in ppdev in order to solve the y2038 issue in
> later patch.
> This patch simply add pp_do_ioctl to compat_ioctl, because I found
> that all the ioctl access the arg as a pointer.
>
> Signed-off-by: Bamvor Zhang Jian <bamvor.zhangjian@linaro.org>
> ---
>  drivers/char/ppdev.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index ae0b42b..9207658 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -69,6 +69,7 @@
>  #include <linux/ppdev.h>
>  #include <linux/mutex.h>
>  #include <linux/uaccess.h>
> +#include <linux/compat.h>
>
>  #define PP_VERSION "ppdev: user-space parallel port driver"
>  #define CHRDEV "ppdev"
> @@ -635,6 +636,11 @@ static long pp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>         return ret;
>  }
>
> +static long pp_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +       return pp_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
> +}
> +
>  static int pp_open (struct inode * inode, struct file * file)
>  {
>         unsigned int minor = iminor(inode);
> @@ -744,6 +750,9 @@ static const struct file_operations pp_fops = {
>         .write          = pp_write,
>         .poll           = pp_poll,
>         .unlocked_ioctl = pp_ioctl,
> +#ifdef CONFIG_COMPAT
> +       .compat_ioctl   = pp_compat_ioctl,
> +#endif

Does adding this patch w/o the following patch break 32bit apps using
this on 64bit kernels?

thanks
-john