linux-kernel - Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

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Date:	Mon, 17 Dec 2012 19:02:45 +0100
From:	Roland Stigge <stigge@...com.de>
To:	Wolfgang Grandegger <wg@...ndegger.com>
CC:	rmallon@...il.com, gregkh@...uxfoundation.org,
	linus.walleij@...aro.org, broonie@...nsource.wolfsonmicro.com,
	w.sang@...gutronix.de, linux-kernel@...r.kernel.org,
	grant.likely@...retlab.ca, daniel-gl@....net, sr@...x.de,
	plagnioj@...osoft.com, linux-arm-kernel@...ts.infradead.org,
	highguy@...il.com
Subject: Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

On 12/17/2012 06:37 PM, Wolfgang Grandegger wrote:
> 	/* Do synchronous data output with a single write access */
> 	__raw_writel(~mask, pio + PIO_OWDR);
> 	__raw_writel(mask, pio + PIO_OWER);
> 	__raw_writel(val, pio + PIO_ODSR);
> 
> For caching we would need a storage. Not sure if it's worth compared to
> a context switch into the kernel.

Block GPIO is not only for you in userspace. ;-) You can also implement
efficient n-bit bus I/O in kernel drivers, n-bit-banging. :-) So not
always context switches involved.

Roland
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