linux-kernel - Re: [PATCH 2/2] iio: exynos-adc: add experimental touchscreen support

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Date:	Mon, 21 Jul 2014 09:19:32 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	devicetree@...r.kernel.org, kgene.kim@...sung.com,
	pawel.moll@....com, ijc+devicetree@...lion.org.uk,
	linux-iio@...r.kernel.org, t.figa@...sung.com,
	rdunlap@...radead.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, robh+dt@...nel.org,
	Chanwoo Choi <cw00.choi@...sung.com>,
	kyungmin.park@...sung.com, linux-samsung-soc@...r.kernel.org,
	Jonathan Cameron <jic23@...nel.org>,
	Ben Dooks <ben-linux@...ff.org>, galak@...eaurora.org,
	ch.naveen@...sung.com, linux-input <linux-input@...r.kernel.org>,
	heiko.stuebner@...com
Subject: Re: [PATCH 2/2] iio: exynos-adc: add experimental touchscreen support

On Mon, Jul 21, 2014 at 05:11:27PM +0200, Arnd Bergmann wrote:
> On Monday 21 July 2014 07:44:42 Dmitry Torokhov wrote:
> > > > 
> > > > It would be nice to actually close the device even if someone is
> > > > touching screen. Please implement open/close methods and have them set a
> > > > flag that you would check here.
> > > 
> > > Ok. I think it's even better to move the request_irq() into the open function,
> > > which will avoid the flag and defer the error handling into the actual opening,
> > > as well as syncing the running irq with the close function.
> > 
> > I do not quite like acquiring resources needed in open. I think drivers should
> > do all resource acquisition in probe() and leave open()/close() to
> > activate/quiesce devices.
> 
> Ok, I'll move it back then. I'm not sure what I'm supposed to do
> in open/close then. Isn't it enough to check info->input->users
> like this?
> 
> static irqreturn_t exynos_ts_isr(int irq, void *dev_id)
> {
>         struct exynos_adc *info = dev_id;
>         struct iio_dev *dev = dev_get_drvdata(info->dev);
>         u32 x, y;
>         bool pressed;
>         int ret;
> 
>         while (info->input->users) {
>                 ret = exynos_read_s3c64xx_ts(dev, &x, &y);
>                 if (ret == -ETIMEDOUT)
>                         break;
> 
>                 pressed = x & y & ADC_DATX_PRESSED;
>                 if (!pressed) {
>                         input_report_key(info->input, BTN_TOUCH, 0);
>                         input_sync(info->input);
>                         break;
>                 }
> 
>                 input_report_abs(info->input, ABS_X, x & ADC_DATX_MASK);
>                 input_report_abs(info->input, ABS_Y, y & ADC_DATY_MASK);
>                 input_report_key(info->input, BTN_TOUCH, 1);
>                 input_sync(info->input);
> 
>                 msleep(1);
>         };
> 
>         writel(0, ADC_V1_CLRINTPNDNUP(info->regs));
> 
>         return IRQ_HANDLED;
> }
> 
> I could do enable_irq()/disable_irq(), but that leaves a small
> race at startup where we request the irq line and then immediately
> disable it again.

I think the above (or a separate flag in driver structure) coupled with
enable/disable IRQ is fine - input core can deal with calls to input_report_*
on devices that have been properly allocated but have not been registered yet.

drivers/input/keyboard/samsung-keypad.c does similar handling.

Thanks.

-- 
Dmitry
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