Hi Thomas,

-----Original Message-----
From: linux-input-owner@vger.kernel.org
[mailto:linux-input-owner@vger.kernel.org] On Behalf Of Thomas Chou
Sent: 2011年6月15日 12:02
To: Baohua Song
Cc: dmitry.torokhov@gmail.com; linux-input@vger.kernel.org; DL-SHA-APBU
Linux; Junyi Zhang; Grant Likely
Subject: Re: [PATCH v2] input: touchscreen: add OF match table for ads7846

On 06/14/2011 02:38 PM, Baohua Song wrote:

quoted

quoted

Could we add an option for gpio
pendown, like this?

- gpios : should specify GPIO used for pendown.

If interrupt node is not present in this node, gpio_to_irq of the pen
down GPIO will be used.

I disagree... An optional gpio node doesn't make sense here. The result of

gpio_to_irq is still an interrupt, then we can place the result in interrupt node.

quoted

And the ads7846 driver required an interrupt node but not a gpio node since

we don't find any of_get_gpio() in this driver.

quoted

BTW, it even doesn’t make sense to call function gpio_to_irq in a driver like

ads7846. on the contrary, drivers/input/keyboard/gpio_keys.c is really an good
user of gpio_to_irq.

Hi Barry,

The classical platform data is seldom used when device tree is passed.
So it would be better to disable platform data passing to verify device
tree support.

Without platform data passing, we don't have pdata and
pdata->get_pendown_state func for ads7846_setup_pendown(). The
ads7846_probe() will need updates on this.

Now the pdata has many fields and several hardware-special callback functions. Non-callback fields can be OF property but callbacks are difficult to be handled in DT. 
So for the moment, we use notifier_block to set pdata in board file as below

static int prima2_touchscreen_notifier_call(struct notifier_block *nb,
                                        unsigned long event, void *__dev)
{
        struct device *dev = __dev;
        struct spi_device *spi = to_spi_device(dev);

        if ((event == BUS_NOTIFY_ADD_DEVICE) &&
            of_device_is_compatible(dev->of_node, "ti,ads7845")) {
                spi->controller_data = &ads7845_ctrldata;
                dev->platform_data = &prima2_ads7845_pdata;
                return NOTIFY_OK;
        }   
        return NOTIFY_DONE;
}

static struct notifier_block prima2_touchscreen_nb = { 
        .notifier_call = prima2_touchscreen_notifier_call,
};

static void __init prima2_touchscreen_init(void)
{
        bus_register_notifier(&spi_bus_type, &prima2_touchscreen_nb);
}

Passing gpio for pendown might be a possible solution, as device tree
supports "gpios" node. We could use of_get_gpio_flags() to retrieve it.

Yes. Since ads7846 must read pendown gpio to get pendown status, gpio is necessary to ads7846 and interrupt is probably repeated copy of gpio since we can get it by gpio_to_irq().
gpio field in pdata may be deleted and moved to DT. that can be another patch after this one is merged. I maybe send it later

I sent an earlier work of mine on this back in Feb. to you.

Best regards,
Thomas

-barry



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