linux-kernel - Re: [PATCH v9 2/9] Input: goodix

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Date:	Mon, 19 Oct 2015 17:52:39 +0300
From:	"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>
To:	"Tirdea, Irina" <irina.tirdea@...el.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bastien Nocera <hadess@...ess.net>,
	Aleksei Mamlin <mamlinav@...il.com>,
	Karsten Merker <merker@...ian.org>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	"Purdila, Octavian" <octavian.purdila@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"Dolca, Robert" <robert.dolca@...el.com>
Subject: Re: [PATCH v9 2/9] Input: goodix - reset device at init

On Mon, Oct 19, 2015 at 02:32:24PM +0000, Tirdea, Irina wrote:
> 
> 
> > -----Original Message-----
> > From: linux-input-owner@...r.kernel.org [mailto:linux-input-owner@...r.kernel.org] On Behalf Of
> > mika.westerberg@...ux.intel.com
> > Sent: 14 October, 2015 16:44
> > To: Dmitry Torokhov
> > Cc: Tirdea, Irina; Bastien Nocera; Aleksei Mamlin; Karsten Merker; linux-input@...r.kernel.org; Mark Rutland; Purdila, Octavian; linux-
> > kernel@...r.kernel.org; devicetree@...r.kernel.org
> > Subject: Re: [PATCH v9 2/9] Input: goodix - reset device at init
> > 
> > On Wed, Oct 14, 2015 at 02:18:20PM +0300, mika.westerberg@...ux.intel.com wrote:
> > > On Tue, Oct 13, 2015 at 11:23:03PM -0700, Dmitry Torokhov wrote:
> > > > I understand why one might use acpi_dev_add_driver_gpios() to augment
> > > > data in ACPI, however here we have completely different issue: driver
> > > > that expects named gpios gets returned gpio that has nothing to do with
> > > > what it requested, because gpiolib acpi code always falls back to
> > > > unnamed gpio if it does not find named gpio. That can be acceptable if
> > > > driver uses the same con_id for all requests to gpiolib, but is not
> > > > working when driver supplies different con_ids.
> > >
> > > Right, the ACPI fallback ignores con_id completely and uses only the
> > > index.
> > >
> > > AFAIK there is only one driver using ACPI _CRS index method:
> > > sdhci-[acpi|pci].c. If we can convert that to use acpi_dev_add_driver_gpios()
> > > to feed names for card detection GPIOs, I think we can remove the
> > > fallback alltogether in favor of named GPIOs for ACPI.
> > 
> > Nah, there seems to be several drivers relying on this already :-/
> 
> Would it be possible to add an optional parameter to the GPIO API
> to specify whether we want to fall back to indexed GPIOs for ACPI?

I don't think it's a good idea to add ACPI specifics to generic APIs.

I went through ACPI enabled drivers calling GPIO APIs and majority of
them are doing this:

static int stk8312_gpio_probe(struct i2c_client *client)
{
        struct device *dev;
        struct gpio_desc *gpio;
        int ret;

        if (!client)
                return -EINVAL;

        dev = &client->dev;

        /* data ready gpio interrupt pin */
        gpio = devm_gpiod_get_index(dev, STK8312_GPIO, 0, GPIOD_IN);
        if (IS_ERR(gpio)) {
                dev_err(dev, "acpi gpio get index failed\n");
                return PTR_ERR(gpio);
        }

        ret = gpiod_to_irq(gpio);
        dev_dbg(dev, "GPIO resource, no:%d irq:%d\n", desc_to_gpio(gpio), ret);

        return ret;
}

We can drop all this because I2C core already handles GpioInt -> interrupt
number translation.

Few drivers are doing something more complex but I think we can still convert
them to use acpi_dev_add_driver_gpios() and eventually get rid of the whole
_CRS index lookup.
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