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path: root/drivers/gpio/pcf857x.c
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2008-02-05gpiolib: pcf857x i2c gpio expander supportDavid Brownell
This is a new-style I2C driver for most common 8 and 16 bit I2C based "quasi-bidirectional" GPIO expanders: pcf8574 or pcf8575, and several compatible models (mostly faster, supporting I2C at up to 1 MHz). The driver exposes the GPIO signals using the platform-neutral GPIO programming interface, so they are easily accessed by other kernel code. The lack of such a flexible kernel API has been a big factor in the proliferation of board-specific drivers for these chips... stuff that rarely makes it upstream since it's so ugly. This driver will let such boards use standard calls. Since it's a new-style driver, these devices must be configured as part of board-specific init. That eliminates the need for error-prone manual configuration of module parameters, and makes compatibility with legacy drivers (pcf8574.c, pc8575.c) for these chips easier (there's a clear either/or disjunction). Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Jean Delvare <khali@linux-fr.org> Cc: Eric Miao <eric.miao@marvell.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Cc: Philipp Zabel <philipp.zabel@gmail.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ben Gardner <bgardner@wabtec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>