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SubjectRe: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins
On Wed, Nov 26, 2008 at 12:51:27AM -0500, Jaya Kumar wrote:
> On Tue, Nov 25, 2008 at 11:15 PM, David Brownell <david-b@pacbell.net> wrote:
> > On Tuesday 25 November 2008, Eric Miao wrote:
> >> Using a bit mask will be more generic if the GPIOs are not contiguous.
> >> Yet I still doubt this will be generic enough to be added to gpiolib.
> >
> > My expectation for this kind of mechanism was that systems who need
> > to craft another parallel bus out of GPIO pins would be doing this
> > with some system-specific utility functions.
> >
> > So my "is it generic enough" question is more at the level of "Are
> > there enough Linux systems that need this sort of thing to justify
> > generic support?". I happen not to have come across the need for
> > such ganged access from Linux (yet). Whereas I've yet to use non-x86
> > Linux systems that don't need to manipulate individual GPIO pins...
>
> I have come across the following scenarios where a bus set of gpio is useful:
> - Broadsheet E-Ink controller (uses 16-bit data bus over GPIO)
> framebuffer device (this patch is for this)
> - Apollo/Hecuba E-Ink controller (uses 8-bit data bus over GPIO)
> framebuffer device
> - 8-bit parallel IO matrix LCD controllers, such as the Samsung KS108,
> also Hitachi, etc

We have such a system at work. And we need fast acces to the gpio pins
when updating the LCD.
I have not written/looked to deep at the code I just recall it was
a bit messy and not something I would be proud of submitting to any ML.

Sam


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