On 03/10/2014 06:37 PM, Felipe Balbi wrote:
> On Mon, Mar 10, 2014 at 10:57:10AM +0200, Roger Quadros wrote:
>> Hi Henrik,
>>
>> On 03/08/2014 05:11 PM, Henrik Rydberg wrote:
>>> Hi Roger,
>>>
>>> the MT implementation seems mostly fine, just one curiosity:
>>>
>>>> static irqreturn_t pixcir_ts_isr(int irq, void *dev_id)
>>>> {
>>>> struct pixcir_i2c_ts_data *tsdata = dev_id;
>>>> const struct pixcir_ts_platform_data *pdata = tsdata->chip;
>>>> + struct pixcir_report_data report;
>>>>
>>>> while (!tsdata->exiting) {
>>>> - pixcir_ts_poscheck(tsdata);
>>>> -
>>>> - if (gpio_get_value(pdata->gpio_attb))
>>>> + /* parse packet */
>>>> + pixcir_ts_parse(tsdata, &report);
>>>> +
>>>> + /* report it */
>>>> + pixcir_ts_report(tsdata, &report);
>>>> +
>>>> + if (gpio_get_value(pdata->gpio_attb)) {
>>>> + if (report.num_touches) {
>>>> + /*
>>>> + * Last report with no finger up?
>>>> + * Do it now then.
>>>> + */
>>>> + input_mt_sync_frame(tsdata->input);
>>>> + input_sync(tsdata->input);
>>>
>>> Why is this special handling needed?
>>
>> This is needed because the controller doesn't always report when all fingers
>> have left the screen. e.g. report might contain 3 fingers touched and then
>> gpio_attb line is de-asserted. There's no report with 0 fingers touched even
>> if the user's fingers have left the screen. So we never detect a BUTTON_UP.
>>
>> Without this s/w workaround we observe side effects like buttons being pressed
>> but not released. To me it looks like a bug in the controller.
>
> the other way would be to *also* use IRQF_TRIGGER_RISING, then you get
> an IRQ when fingers leave the screen. No ?
>
Yes that is also possible but it involves an additional interrupt context switch.
Sometimes the controller does report 0 finger touches before de-asserting the ATTB line and so
this additional interrupt is not needed by the approach I used.
cheers,
-roger
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