[PATCH libevdev 6/8] Work around missing EVIOCGMTSLOTS ioctl

[David Herrmann]

Hi

On Mon, Oct 14, 2013 at 8:14 AM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>  libevdev/libevdev.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/libevdev/libevdev.c b/libevdev/libevdev.c
> index 29640f4..6f203e2 100644
> --- a/libevdev/libevdev.c
> +++ b/libevdev/libevdev.c
> @@ -498,11 +498,14 @@ sync_mt_state(struct libevdev *dev, int create_events)
>  {
>         int rc;
>         int i;
> +       int ioctl_success = 0;
>         struct mt_state {
>                 int code;
>                 int val[MAX_SLOTS];
>         } mt_state[ABS_MT_CNT];
>
> +       memset(&mt_state, 0, sizeof(mt_state));
> +
>         for (i = ABS_MT_MIN; i <= ABS_MT_MAX; i++) {
>                 int idx;
>                 if (i == ABS_MT_SLOT)
> @@ -514,8 +517,15 @@ sync_mt_state(struct libevdev *dev, int create_events)
>                 idx = i - ABS_MT_MIN;
>                 mt_state[idx].code = i;
>                 rc = ioctl(dev->fd, EVIOCGMTSLOTS(sizeof(struct mt_state)), &mt_state[idx]);
> -               if (rc < 0)
> -                       goto out;
> +               if (rc < 0) {
> +                       /* if the first ioctl fails with -EINVAL, chances are the kernel
> +                          doesn't support the ioctl. Simply continue */
> +                       if (errno == -EINVAL && !ioctl_success) {
> +                               rc = 0;

Why not check whether dev->num_slots is 0? Or isn't this guaranteed?
If it's not, you need to clear mt_state here.

> +                       } else /* if the second, ... ioctl fails, really fail */
> +                               goto out;
> +               } else if (ioctl_success == 0)
> +                       ioctl_success = 1;
>         }
>
>         for (i = 0; i < dev->num_slots; i++) {
> --
> 1.8.3.1
>
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