Re: [PATCH] edt_ts: EDT Touchscreen driver

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 [off-list ref] wrote:

quoted

On Tue, Nov 15, 2011 at 01:07:57AM +0400, Ilya Yanok wrote:

quoted

Hi Dmitry,

On 14.11.2011 21:28, Dmitry Torokhov wrote:

quoted

quoted

+	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.

So what ensures that the gpio line stays low between the check and the
time you get access to i2c bus and get around reading the data.

The designer of the target device
insisted on driver implementation reading touch packet data only
when irq line is pulled down.

Well... have you tried checkign whether it is really necessary. Because
if it is not necessary you could do away with the platform data
altogether.

Thanks.

-- 
Dmitry