Re: [PATCH v9 2/9] Input: goodix - reset device at init

mika.westerberg
2015-10-19T14:52:50Z

On Mon, Oct 19, 2015 at 02:32:24PM +0000, Tirdea, Irina wrote:
>
>
> > -----Original Message-----
> > From: linux-input-owner@vger.kernel.org [mailto:linux-input-owner@vger.kernel.org] On Behalf Of
> > mika.westerberg@linux.intel.com
> > Sent: 14 October, 2015 16:44
> > To: Dmitry Torokhov
> > Cc: Tirdea, Irina; Bastien Nocera; Aleksei Mamlin; Karsten Merker; linux-input@vger.kernel.org; Mark Rutland; Purdila, Octavian; linux-
> > kernel@vger.kernel.org; devicetree@vger.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@linux.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.