Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins

On Fri, Nov 28, 2008 at 07:43:31AM +0800, Jaya Kumar wrote:

On Fri, Nov 28, 2008 at 4:01 AM, Sam Ravnborg [off-list ref] wrote:

quoted

On Wed, Nov 26, 2008 at 12:51:27AM -0500, Jaya Kumar wrote:

quoted

On Tue, Nov 25, 2008 at 11:15 PM, David Brownell [off-list ref] wrote:

quoted

On Tuesday 25 November 2008, Eric Miao wrote:

quoted

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

Okay. Please help me understand in case I misunderstood. Are you
saying the code that I posted is too messy? To me, actually I am proud
of it. :-) But if some parts look messy, I'm happy to work on
improving it. I will need some advice though and please advise me on
which parts look messy.

Nope - the code we use at work is too messy. What you posted looks
much better.

	Sam