On Mon, Sep 28, 2009 at 09:00:01PM +0200, Linus Walleij wrote:

Hm thinking back at this:

2009/9/27 Russell King - ARM Linux [off-list ref]:

quoted

The real problem is that U300 doesn't implement gpio_is_valid() -
which is part of the GPIO API and not specific to GPIOLIB.

None of the GPIO drivers in drivers/gpio implement gpio_is_valid()
though they all select GPIOLIB which in turn selects GENERIC_GPIO.

include/asm-generic/gpio.h:

#ifdef CONFIG_GPIOLIB
...
/* Platforms may implement their GPIO interface with library code,
 * at a small performance cost for non-inlined operations and some
 * extra memory (for code and for per-GPIO table entries).
 *
 * While the GPIO programming interface defines valid GPIO numbers
 * to be in the range 0..MAX_INT, this library restricts them to the
 * smaller range 0..ARCH_NR_GPIOS-1.
 */

#ifndef ARCH_NR_GPIOS
#define ARCH_NR_GPIOS           256
#endif

static inline int gpio_is_valid(int number)
{
        /* only some non-negative numbers are valid */
        return ((unsigned)number) < ARCH_NR_GPIOS;
}

So, with gpiolib enabled, gpio_is_valid() is predefined assuming that
GPIOs between 0..ARCH_NR_GPIOS are valid.