linux-kernel - Re: [PATCH] ACPI / GPIO: Driver GPIO mappings for ACPI GPIOs

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Date:	Mon, 3 Nov 2014 14:22:10 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Alexandre Courbot <gnurou@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Grant Likely <grant.likely@...aro.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] ACPI / GPIO: Driver GPIO mappings for ACPI GPIOs

On Sat, Oct 25, 2014 at 12:05 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Provide a way for device drivers using GPIOs described by ACPI
> GpioIo resources in _CRS to tell the GPIO subsystem what names
> (connection IDs) to associate with specific GPIO pins defined
> in there.
>
> To do that, a driver needs to define a mapping table as a
> NULL-terminated array of struct acpi_gpio_mapping objects
> that each contain a name, a pointer to an array of pin data
> (struct acpi_gpio_params) objects and the size of that array.
>
> Each struct acpi_gpio_params object consists of three fields,
> crs_entry_index, pin_index, active_low, representing the index of

I prefer that you call the second thing "line_index" rather than
"pin_index". Not all GPIOs in the world are tied to physical pins.
Also it is easy to confuse stuff with the pin control terminology
if it's called "pin".

> the target GpioIo()/GpioInt() resource in _CRS starting from zero,
> the index of the target pin in that resource starting from zero,
> and the active-low flag for that pin, respectively.
>
> Next, the mapping table needs to be passed as the second argument to
> acpi_dev_add_driver_gpios() that will register it with the ACPI device
> object pointed to by its first argument.  That object must represent
> the ACPI namespace node containing the _CRS object referred to by the
> GPIO mapping.  That should be done in the driver's .probe() routine.
>
> On removal, the driver should unregister its GPIO mapping table
> by calling acpi_dev_remove_driver_gpios() on the ACPI device
> object where that table was previously registered.
>
> Included are fixes from Mika Westerberg.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

And "pin" is mentioned several times in the commit message.
I prefer that we talk about "lines".

(...)

> +struct acpi_gpio_params {
> +       unsigned int crs_entry_index;
> +       unsigned int pin_index;

So line_index;

> +       bool active_low;
> +};

With that change:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij
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