linux-kernel - Re: [RFC 2.6.28 1/2] gpiolib: add set/get batch v4

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Date:	Mon, 19 Jan 2009 07:48:50 +0800
From:	Jaya Kumar <jayakumar.lkml@...il.com>
To:	Ryan Mallon <ryan@...ewatersys.com>
Cc:	David Brownell <david-b@...bell.net>,
	Eric Miao <eric.miao@...vell.com>,
	Paulius Zaleckas <paulius.zaleckas@...tonika.lt>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Sam Ravnborg <sam@...nborg.org>,
	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 2.6.28 1/2] gpiolib: add set/get batch v4

On Mon, Jan 19, 2009 at 7:46 AM, Jaya Kumar <jayakumar.lkml@...il.com> wrote:
> On Mon, Jan 19, 2009 at 4:05 AM, Ryan Mallon <ryan@...ewatersys.com> wrote:
>> Jaya Kumar wrote:
>>> Hi friends,
>>>
>>
>>> +
>>> +     /* BATCH GPIO OUTPUT */
>>> +int gpio_set_batch(unsigned gpio, u32 values, u32 bitmask, int maskwidth);
>>> +
>>> +The following examples help explain how this function is to be used.
>>> + Q: How to set gpio pins 0 through 7 to all 0? (8 bits)
>>> + A: gpio_set_batch(gpio=0, values=0x0, bitmask=0xFF, width=8);
>>> + Q: How to set gpio pins 58 through 73 to all 1? (16 bits)
>>> + A: gpio_set_batch(gpio=58, values=0xFFFF, bitmask=0xFFFF, width=16);
>>> + Q: How to set gpio pins 16 through 47 to 0xCAFEC001? (32 bits)
>>> + A: gpio_set_batch(gpio=16, values=0xCAFEC001, bitmask=0xFFFFFFFF, width=32);
>>> +
>>
>> Can the gpio_set_batch function be used to set non-consecutive gpios?
>> For example:
>>
>>  gpio_set_batch(0, 0x0, 0x88, 8);
>>
>> To clear gpios 3 and 7? It looks like the pxa implementation will
>
> Hi Ryan,
>
> For the first part, yes, it can do non-consecutive gpios by using the
> mask. Pins 3 and 7 are handled using a 5-bit mask. You'd  do
> gpio_set_batch(3 <- starting pin is gpio 3, 0x0 <- clear, 0x1F <-
> mask, 5 <- bit width of mask);

Correction: I meant to write 0x11 for the mask above (instead of 0x1F)
since you only want to clear the starting pin 3 and the ending pin 7
in the 5 bits. If we used 0x1F here, then we would clear all 5 bits
rather than just 3 and 7.

Thanks,
jaya
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