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From: David Brownell <david-b@pacbell.net>
To: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch 2.6.24-rc2 1/3] generic gpio -- gpio_chip support
Date: Wed, 14 Nov 2007 23:17:13 -0800
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Cc: Andrew Morton <akpm@linux-foundation.org>,
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On Wednesday 14 November 2007, Thomas Gleixner wrote:
> struct gpio_desc {
>        struct gpio_chip *chip;
>        int pinoffset;
> };

Eric Miao has a different notion of "gpio_desc" more analagous to
the "irq_desc", so I'll not use that name for such a structure.

Let me call yours a "struct gpio_pin" instead -- purely for some
discussion here.


There's been some desire for a "gpio_pin" struct for entirely
different reasons ... as the identifiers passed into a slightly
different type of GPIO programming interface.  So for example

  static inline void gpiopin_set_value(struct gpio_pin *p, int v)
  {
	p->chip->set(p->chip, p->pinoffset, v);
  }

One reason to be interested in gpio_chip is that it it would
easily support interoperation between traditional GPIO ID schemes
(numbered to match the SOC at the heart of a given board) and
more dynamic ones that might be needed to use curiousities like
a set of USB-to-GPIO adapters.

- Dave