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

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Date:	Mon, 29 Dec 2008 11:59:36 -0800
From:	David Brownell <david-b@...bell.net>
To:	Ben Nizette <bn@...sdigital.com>
Cc:	Robin Getz <rgetz@...ckfin.uclinux.org>,
	Jaya Kumar <jayakumar.lkml@...il.com>,
	Eric Miao <eric.y.miao@...il.com>,
	Sam Ravnborg <sam@...nborg.org>,
	Eric Miao <eric.miao@...vell.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Philipp Zabel <philipp.zabel@...il.com>,
	Russell King <rmk@....linux.org.uk>,
	Ben Gardner <bgardner@...tec.com>, Greg KH <greg@...ah.com>,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, linux-embedded@...r.kernel.org
Subject: Re: [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins

On Sunday 28 December 2008, Ben Nizette wrote:
> > > gpio_set_batch(DB0, value, 0xFFFF, 16)
> > > 
> > > which has the nice performance benefit of skipping all the bit
> > > counting in the most common use case scenario.
> > 
> > but has the requirement that the driver know exactly the board level 
> > impmentation details (something that doesn't sound generic).
> 
> The original use case for these batch operations was in a fastpath -
> setting data lines on a framebuffer.

And the rationale for generalizing them was to let such fastpaths
stop being board-specific hacks.  :)


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