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

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 <redacted>
Tested-by: Wen He <redacted>
---
 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

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