Date: Thu, 26 Nov 2009 06:57:36 +0200 From: Oleksandr Tymoshenko <gonzo@freebsd.org> To: arch@freebsd.org Cc: embedded@frebsd.org Subject: [RFC] GPIO framework Message-ID: <20091126045736.GA25431@bluezbox.com>
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Recently I've been working on GPIO framework that, I believe, is much needed for embedded applications of FreeBSD. Now framework is mature enough to show it to the world, so this is my request for review. Patch: http://people.freebsd.org/~gonzo/mips/gpio.diff sys/gpio.h is based on the same file from NetBSD but all the other files have been written from the scratch. Description: GPIO stands for General Purpose Input/Output. This interface may be thought of as a set of pins which could serve as input or output having logical 0 and logical 1 as their values (some other options are applicable, but they're not crucial for this explanation). Most common usage of GPIO interface is LED and button control for various SoCs. Architecture: I tried to separate hardware implementation from logic as much as possible. All the HW-independent stuff resides in sys/dev/gpio directory. It consists of gpioc (GPIO controller device), gpiobus (bus that manages devices attached to GPIO controller) and gpioled (implementation of LED driver that illustrates usage pattern of gpiobus, utilizes led(4) interface). HW-dependent part might be a part of SoC, I2C extender, whatever. It should implement interface defined in sys/dev/gpio/gpio_if.m: gpio_pin_max - get maximum pin available gpio_pin_getcaps - get capabilities for given pin gpio_pin_getflags - get flags for given pin gpio_pin_setflags - set flags for given pin gpio_pin_getname - get pin name (if any) gpio_pin_set - set pin value gpio_pin_get - get pin value gpio_pin_toggle - toggle(invert) pin value And on attaching HW driver should add gpioc and gpiobus as its children. gpioc creates /dev/gpiocX entry that is used by gpioctl application for managing GPIO pins using following ioctls: GPIOMAXPIN - get maximum pin available GPIOGETCONFIG - get flags/capabilities/name for given pin GPIOSETCONFIG - set flags for given pin GPIOGET - get pin value GPIOSET - set pin value GPIOTOGGLE - toggle(invert) pin value gpioctl usage: gpioctl -f ctldev -l [-v] gpioctl -f ctldev -t pin gpioctl -f ctldev -c pin flag ... gpioctl -f ctldev pin [0|1] gpiobus manages devices attached to gpio controller. Its interface is a subset of of gpio_if.m interface and allows child devices talk to GPIO controller. At the moment children could be set only by hints file and pin space is limited to 32. Example: # RF led hint.gpioled.0.at="gpiobus0" hint.gpioled.0.name="rf" # pin 2 hint.gpioled.0.pins=0x0004 Interface functions: gpiobus_pin_getcaps - get capabilities for given pin gpiobus_pin_getflags - get flags for given pin gpiobus_pin_setflags - set flags for given pin gpiobus_pin_set - set pin value gpiobus_pin_get - get pin value gpiobus_pin_toggle - toggle(invert) pin value Reference implementation of child device is sys/dev/gpio/gpioled.c It provides on/off function for led(4) API Any comments/feedback are welcome -- gonzo
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