[GIT PULL] omap changes for v2.6.39 merge window
u.kleine-koenig at pengutronix.de
Fri Apr 1 17:00:36 EDT 2011
On Fri, Apr 01, 2011 at 03:54:47PM -0400, Nicolas Pitre wrote:
> It would be more useful and scalable to simply sit down, look at the
> current mess, and identify common patterns that can be easily factored
> out into some shared library code, and all that would be left in the
> board or SOC specific files eventually is the data to register with that
> library code. Nothing so complicated as grand plans or planification
> that makes it look like a mountain.
> Two patterns were identified so far, and they are:
> 1) GPIO drivers
> As Linus observed, in the majority of the cases GPIOs are accessed
> through simple memory-mapped registers. Some have absolute state
> registers, the others have separate clear/set registers. Suffice to
> create two generic GPIO drivers each covering those two common cases,
> and those generic drivers would simply register with the higher level
> gpiolib code, and all the board code would have to do is to provide
> the data for those GPIOs (register offsets, number of GPIOs, etc.).
> Whether this data eventually comes from DT is an orthogonal issue.
> 2) IRQ chip drivers
> Again, as Thomas observed, the same issue exists with the majority of
> the IRQ chip drivers. Most of them follow a common simple pattern
> that can be abstracted in some generic library code due to their very
> similar mode of operation. Writing a common driver would leave the
> board specific code with only a data table describing hardware
> A good example of such rationalization that already happened is the
> leds-gpio driver (./drivers/leds/leds-gpio.c), or similarly the
> gpio-keys driver (drivers/input/keyboard/gpio_keys.c). I remember when
> those board files were implementing their own simple drivers hooking
> directly to the input API or the LED API.
> After that let's take another identified common pattern and factorize it
> out from board code. That might be timers (see RMK's recent
> sched_clock() rationalization). That might be clocks (patches from
> Jeremy Kerr exist and need merged). Etc.
Another one is pwm (git ls-files arch/arm | grep pwm). A general
pwm framework was already discussed on lkml and linux-embedded
I don't know the details though.
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