linux-kernel - Re: [patch/rfc 1/4] GPIO implementation framework

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Date:	Tue, 27 Nov 2007 09:26:30 -0800
From:	David Brownell <david-b@...bell.net>
To:	"eric miao" <eric.y.miao@...il.com>
Cc:	"Linux Kernel list" <linux-kernel@...r.kernel.org>,
	"Felipe Balbi" <felipebalbi@...rs.sourceforge.net>,
	"Bill Gatliff" <bgat@...lgatliff.com>,
	"Haavard Skinnemoen" <hskinnemoen@...el.com>,
	"Andrew Victor" <andrew@...people.com>,
	"Tony Lindgren" <tony@...mide.com>,
	"Jean Delvare" <khali@...ux-fr.org>,
	"Kevin Hilman" <khilman@...sta.com>,
	"Paul Mundt" <lethal@...ux-sh.org>,
	"Ben Dooks" <ben@...nity.fluff.org>
Subject: Re: [patch/rfc 1/4] GPIO implementation framework

Thanks, I'll be looking at it ... the one thing I strongly dislike is
this change:

On Tuesday 27 November 2007, eric miao wrote:
> 4. use a loop for "gpio_desc[]" instead of a loop for "gpio_chips[]" in
>    gpiolib_show(), change is straight forward; since it is now per gpio
>    based, the gpio_chip.dbg_show() is removed as well

That removes the ability to display all kinds of significant
chip-specific state ... like whether a given signal has active
pullups or pulldowns, uses open-drain signaling, and so forth.

It also makes access a lot slower ... e.g. rather than one
batch of I2C or SPI operations for all N signals on a chip,
it's got to do N batches.

Plus it just needlessly breaks existing code.

I'll put together a version without that problem.

- Dave
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