Re: [PATCH v2 2/3] HID: multitouch: add control of the feature "Maximum Contact Number"

Hi Henrik,

On Fri, Jan 20, 2012 at 17:19, Henrik Rydberg [off-list ref] wrote:

Hi Benjamin,

quoted

If the programmer fills the field maxcontacts in the mt_class,
then the driver will set the feature to this value. It is safe
for current drivers as the feature is read/right in the HID norm

read/write, I presume.

you're right... ;-)

quoted

@@ -609,6 +612,36 @@ static void mt_set_input_mode(struct hid_device *hdev)

      }
 }

+static void mt_set_maxcontacts(struct hid_device *hdev)
+{
+     struct mt_device *td = hid_get_drvdata(hdev);
+     struct hid_report *r;
+     struct hid_report_enum *re;
+     int fieldmax, max;
+
+     if (td->maxcontact_report_id < 0)
+             return;
+
+     if (!td->mtclass.maxcontacts)
+             return;
+
+     re = &(hdev->report_enum[HID_FEATURE_REPORT]);

Why parenthesis here?

ok

quoted

+     r = re->report_id_hash[td->maxcontact_report_id];
+     if (r) {
+             max = td->mtclass.maxcontacts;
+             fieldmax = r->field[0]->logical_maximum;
+             hid_info(hdev, "%s: value = %d / %d / %d\n", __func__,
+                     r->field[0]->value[0],
+                     td->mtclass.maxcontacts,
+                     fieldmax);

Looks like debug information, please downplay or remove.

I can remove them if you need.

quoted

+             max = fieldmax < max ? fieldmax : max;

There are kernel variants of min/max functions to consider here.

I'll look for them.

quoted

+             if (r->field[0]->value[0] != max) {
+                     r->field[0]->value[0] = max;
+                     usbhid_submit_report(hdev, r, USB_DIR_OUT);
+             }

So the report is in fact only set when different... Do we know for
which current devices this is true?

Currently, I've got only the Perixx touchpad that needs this feature
to be set. The initial value is 0 whereas it should be 2.

Maybe some drivers that used the DUAL_MT_CLS_* can handle more, but I
have no idea has I don't have many of them.

Cheers,
Benjamin

Thanks,
Henrik

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