[firstname.lastname@example.org: [RFC] GPIO framework]
marc at msys.ch
Fri Nov 27 21:31:39 UTC 2009
Oleksandr Tymoshenko schrieb:
> Forwarding RFC to embedded@ because there was typo in Cc address in
> the original message :(
> ----- Forwarded message from Oleksandr Tymoshenko <gonzo at freebsd.org> -----
> Date: Thu, 26 Nov 2009 06:57:36 +0200
> From: Oleksandr Tymoshenko <gonzo at freebsd.org>
> To: arch at freebsd.org
> Cc: embedded at frebsd.org
> Subject: [RFC] GPIO framework
> User-Agent: Mutt/1.5.20 (2009-06-14)
> 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.
> 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.
we do much more, since years: we attach I2C buses over GPIO, or 1-Wire
buses. GPIO is not just for LEDs.
> 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
> 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
> # pin 2
> 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
it suffers from the same problems my implementation in other BSD
suffers: No interrupt capabilities, no capability to build buses wider
than 1 bit.
your gpioctl command line syntax is not nice.
I suggest you take a closer look at gpio in NetBSD and that we work
together on this. My offer stands.
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