linux-kernel - Re: [PATCH 1/2] gpio-ich: Check for pin availability at request time

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Message-ID: <1362507414.28106.62.camel@petert>
Date:	Tue, 05 Mar 2013 12:16:54 -0600
From:	Peter Tyser <ptyser@...-inc.com>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 1/2] gpio-ich: Check for pin availability at request time

Hi Jean,

On Tue, 2013-03-05 at 09:06 +0100, Jean Delvare wrote:
> Stop checking for pin availability in get functions. These functions
> can be called repeatedly, so checking every time is bad for
> performance.
> 
> Instead, check at pin request time. This only happens once, and we can
> let the caller know of the unavailability much earlier.

Is there a reason to not remove the ichx_gpio_check_available() calls
from the ichx_gpio_direction_output() and ichx_gpio_direction_input()
functions in this change?

I had originally assumed these checks were to support the "legacy"
interface where users could use the GPIOs without first requesting the
GPIO, but after looking a bit further it looks like the gpiolib code to
set a GPIO as an input or output does auto-request the GPIO before
setting its direction.  So I'd assume your 1 check in 
ichx_gpio_request() would cover the "legacy" interface too.

Best,
Peter

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