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

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Message-ID: <45a44e480812302058k365eddcfxf902095657b78534@mail.gmail.com>
Date:	Tue, 30 Dec 2008 23:58:44 -0500
From:	"Jaya Kumar" <jayakumar.lkml@...il.com>
To:	"Robin Getz" <rgetz@...ckfin.uclinux.org>
Cc:	"David Brownell" <david-b@...bell.net>,
	"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 Tue, Dec 30, 2008 at 11:55 PM, Robin Getz <rgetz@...ckfin.uclinux.org> wrote:
> Yeah, I hadn't thought about spanning more than one gpio_chip. That's a good
> point.

The currently posted code already supports spanning more than one gpio_chip.

+       do {
+               chip = gpio_to_chip(gpio + i);
+               WARN_ON(extra_checks && chip->can_sleep);
+
+               if (!chip->set_bus) {
+                       while (((gpio + i) < (chip->base + chip->ngpio))
+                               && bitwidth) {
+                               value = values & (1 << i);
+                               chip->set(chip, gpio + i - chip->base, value);
+                               i++;
+                               bitwidth--;
+                       }
+               } else {
+                       value = values >> i; /* shift off the used stuff */
+                       remwidth = ((chip->base + (int) chip->ngpio) -
+                                       ((int) gpio + i));
+                       width = min(bitwidth, remwidth);
+
+                       chip->set_bus(chip, gpio + i - chip->base, value,
+                                       width);
+                       i += width;
+                       bitwidth -= width;
+               }
+       } while (bitwidth);
--
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