On embedded devices, sleep mode conditions can be tricky to handle,
Especially when processors tend to pull-down the w1 bus during sleep.  Bus
slaves (such as the ds2760) may interpret this as a reason for power-down
conditions and entirely switch off the device.

This patch adds a callback function pointer to let users switch on and off
the external pull-up resistor.  This lets the outside world know whether
the processor is currently actively driving the bus or not.

When this callback is not provided, the code behaviour won't change.
Signed-off-by: NDaniel Mack <daniel@caiaq.de>
Acked-by: NVille Syrjala <syrjala@sci.fi>
Acked-by: NEvgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add a GPIO 1-wire bus master driver.  The driver used the GPIO API to
control the wire and the GPIO pin can be specified using platform data
similar to i2c-gpio.  The driver was tested with AT91SAM9260 + DS2401.
Signed-off-by: NVille Syrjala <syrjala@sci.fi>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>