Hi Peter,
On Fri, May 15, 2020 at 12:49 AM Peter Hutterer
<peter.hutterer@xxxxxxxxx> 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@xxxxxxxxx>
> Tested-by: Wen He <wen.he_1@xxxxxxx>
> ---
> Same patch as before, but this time with diff.noprefix set to false again.
> Too bad that setting messes up format-patch :( Apologies for the broken
> one.
Thanks for the quick respin. I was about to apply it, and then I
realized that something was off (see inlined)
>
> drivers/hid/hid-input.c | 22 ++++++++++++----------
> 1 file changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index dea9cc65bf80..a54824d451bf 100644
> --- a/drivers/hid/hid-input.c
> +++ b/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);
I think here we said that the reading of this particular feature was
mandatory by Microsoft, but what if a device doesn't like it.
I wonder if we should not guard this against HID_QUIRK_NO_INIT_REPORTS
too, in the event we need to quirk a particular device.
(BTW, I prefer this version compared to the first draft you sent me :-P )
Cheers,
Benjamin
> + hid_hw_wait(hid);
> + get_report_completed = true;
> + }
> +
> report->field[i]->value[j] = value;
> update_needed = true;
> }
> --
> 2.26.2
>
