From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Subject: Re: [PATCH] edt_ts: EDT Touchscreen driver
Date: Tue, 15 Nov 2011 01:30:14 -0800
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To: Anatolij Gustschin <agust@denx.de>
Cc: Ilya Yanok <yanok@emcraft.com>, linux-input@vger.kernel.org, wd@denx.de, dzu@denx.de, sasha_d@emcraft.com

On Tue, Nov 15, 2011 at 10:17:15AM +0100, Anatolij Gustschin wrote:
> Hi Dmitry,
> 
> On Mon, 14 Nov 2011 13:32:42 -0800
> Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
> 
> > On Tue, Nov 15, 2011 at 01:07:57AM +0400, Ilya Yanok wrote:
> > > Hi Dmitry,
> > > 
> > > On 14.11.2011 21:28, Dmitry Torokhov wrote:
> > > >> +	irq = gpio_to_irq(pdata->irq_gpio);
> > > >> +	if (irq < 0) {
> > > >> +		dev_err(&client->dev, "can't get IRQ for GPIO\n");
> > > >> +		error = -EINVAL;
> > > >> +		goto err0;
> > > >> +	}
> > > > 
> > > > Why can't we use client->irq?
> > > 
> > > Well, my idea was to avoid duplication (passing both GPIO and IRQ
> > > numbers) and I can't pass only client->irq as we need GPIO number also
> > > and irq_to_gpio is not guaranteed to work with arbitrary IRQ number.
> > 
> > Do you really need to read gpio state in IRQ? Can't you simply rely on
> > 'event' do decide whether to emit input events?
> 
> We can't rely on the 'event' only. The peculiar behaviour of the
> touch controller enforces this. The touch controller toggles the
> interrupt line when you keep the finger down. The rate is not exactly
> specified by the the manufacturer (~80/sec). Measured rate deviates
> from this specified rate. Valid touch packet data can be read when
> interrupt line is pulled down. The designer of the target device
> insisted on driver implementation reading touch packet data only
> when irq line is pulled down.
> 
> > Also:
> > 
> > - please do not report fake pressure events since the device does
> > not seem to support true pressure reading (tslib has been fixed ages
> > ago).
> 
> Many projects still use tslib-1.0 (e.g. distributions based on
> recent yoctoproject releases). Removing pressure event reporting
> will certainly break touch screen support there.

Then I recommend notifying yoctoproject that they need to update tslib
to something not so ancient.

Thanks.

-- 
Dmitry