linux-kernel - Re: [PATCH v2] HID: core: check whether usage page item is after usage id item

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Date:   Fri, 11 Oct 2019 10:08:41 +0800
From:   Candle Sun <candlesea@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        orson.zhai@...soc.com,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Candle Sun <candle.sun@...soc.com>,
        Nianfu Bai <nianfu.bai@...soc.com>
Subject: Re: [PATCH v2] HID: core: check whether usage page item is after
 usage id item

On Thu, Oct 10, 2019 at 8:17 PM Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
>
> On Thu, Oct 10, 2019 at 5:19 AM Candle Sun <candlesea@...il.com> wrote:
> >
> > On Thu, Oct 10, 2019 at 2:00 AM Jiri Kosina <jikos@...nel.org> wrote:
> > >
> > > On Wed, 9 Oct 2019, Nicolas Saenz Julienne wrote:
> > >
> > > > > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> > > > > index 3eaee2c..3394222 100644
> > > > > --- a/drivers/hid/hid-core.c
> > > > > +++ b/drivers/hid/hid-core.c
> > > > > @@ -35,6 +35,8 @@
> > > > >
> > > > >  #include "hid-ids.h"
> > > > >
> > > > > +#define GET_COMPLETE_USAGE(page, id) (((page) << 16) + ((id) & 0xffff))
> > > >
> > > > Not sure I like the macro. I'd rather have the explicit code. That said, lets
> > > > see what Benjamin has to say.
> > >
> > > Not sure about Benjamin :) but I personally would ask for putting it
> > > somewhere into hid.h as static inline.
> > >
> > > And even if it's for some reason insisted on this staying macro, please at
> > > least put it as close to the place(s) it's being used as possible, in
> > > order to maintain some code sanity.
> > >
> > > Thanks,
> > >
> > > --
> > > Jiri Kosina
> > > SUSE Labs
> > >
> >
> > Thanks Nicolas and Jiri,
> > If macro is not good, I will change it to static function. But the
> > funciton is only used in hid-core.c,
> > maybe placing it into hid.h is not good?
>
> I would rather use a function too (in hid-core.c, as it's not reused
> anywhere else), and we can make it simpler from the caller point of
> view (if I am not mistaken):
> ---
> static void concatenate_usage_page(struct hid_parser *parser, int index)
> {
>     parser->local.usage[index] &= 0xFFFF;
>     parser->local.usage[index] |= (parser->global.usage_page & 0xFFFF) << 16;
> }
>
> // Which can then be called as:
> +       parser->local.usage[parser->local.usage_index] = usage;
> +       if (size <= 2)
> +               concatenate_usage_page(parser, parser->local.usage_index);
> +
>
> // And
>         for (i = 0; i < parser->local.usage_index; i++)
> -               if (parser->local.usage_size[i] <= 2)
> -                       parser->local.usage[i] +=
> parser->global.usage_page << 16;
> +               if (parser->local.usage_size[i] <= 2) {
> +                       concatenate_usage_page(parser, i);
> +               }
>  }
> ---
>
> And now that I have written this, the check on the size could also be
> very well integrated in concatenate_usage_page().
>
> Cheers,
> Benjamin
>

Thanks Benjamin's detailed directions. I will amend the patch.

Candle

> >
> > Regards,
> > Candle
>