Re: [PATCH] HID: input: do not run GET_REPORT unless there's a Resolution Multiplier

From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
To: Peter Hutterer <peter.hutterer@who-t.net>
Cc: "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
	Jiri Kosina <jikos@kernel.org>, Wen He <wen.he_1@nxp.com>
Subject: Re: [PATCH] HID: input: do not run GET_REPORT unless there's a Resolution Multiplier
Date: Thu, 14 May 2020 14:31:15 +0200	[thread overview]
Message-ID: <CAO-hwJJjoEyoKokK6DS_Kb0su2bkC2wzMx-gzaWQcG+dn5vVdw@mail.gmail.com> (raw)
In-Reply-To: <20200514111448.GA855579@jelly>

Hey,

On Thu, May 14, 2020 at 1:14 PM Peter Hutterer <peter.hutterer@who-t.net> wrote:
>
> hid-multitouch currently runs GET_REPORT for Contact Max and again to
> retrieve the Win8 blob. If both are within the same report, the
> Resolution Multiplier code calls GET_FEATURE again and this time,
> possibly due to timing, it causes the ILITEK-TP device interpret the
> GET_FEATURE as an instruction to change the mode and effectively stop
> the device from functioning as expected.
>
> Notably: the device doesn't even have a Resolution Multiplier so it
> shouldn't be affected by any of this at all.
>
> Fix this by making sure we only execute GET_REPORT if there is
> a Resolution Multiplier in the respective report.
>
> Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
> Tested-by: Wen He <wen.he_1@nxp.com>
> ---
>  drivers/hid/hid-input.c | 22 ++++++++++++----------
>  1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git drivers/hid/hid-input.c drivers/hid/hid-input.c

Seems like you git format-patch is still busted, you are lacking the
'a/' and 'b/' in front of the files, and so the patch fails to apply
because 'hid/hid-input.c' is not in the tree.

Cheers,
Benjamin

> index dea9cc65bf80..a54824d451bf 100644
> --- drivers/hid/hid-input.c
> +++ drivers/hid/hid-input.c
> @@ -1560,21 +1560,12 @@ static bool __hidinput_change_resolution_multipliers(struct hid_device *hid,
>  {
>         struct hid_usage *usage;
>         bool update_needed = false;
> +       bool get_report_completed = false;
>         int i, j;
>
>         if (report->maxfield == 0)
>                 return false;
>
> -       /*
> -        * If we have more than one feature within this report we
> -        * need to fill in the bits from the others before we can
> -        * overwrite the ones for the Resolution Multiplier.
> -        */
> -       if (report->maxfield > 1) {
> -               hid_hw_request(hid, report, HID_REQ_GET_REPORT);
> -               hid_hw_wait(hid);
> -       }
> -
>         for (i = 0; i < report->maxfield; i++) {
>                 __s32 value = use_logical_max ?
>                               report->field[i]->logical_maximum :
> @@ -1593,6 +1584,17 @@ static bool __hidinput_change_resolution_multipliers(struct hid_device *hid,
>                         if (usage->hid != HID_GD_RESOLUTION_MULTIPLIER)
>                                 continue;
>
> +                       /*
> +                        * If we have more than one feature within this report we
> +                        * need to fill in the bits from the others before we can
> +                        * overwrite the ones for the Resolution Multiplier.
> +                        */
> +                       if (!get_report_completed && report->maxfield > 1) {
> +                               hid_hw_request(hid, report, HID_REQ_GET_REPORT);
> +                               hid_hw_wait(hid);
> +                               get_report_completed = true;
> +                       }
> +
>                         report->field[i]->value[j] = value;
>                         update_needed = true;
>                 }
> --
> 2.26.2
>