From: Antti Palosaari <crope@iki.fi>
To: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: "Frank Schäfer" <fschaefer.oss@googlemail.com>,
linux-media@vger.kernel.org
Subject: Re: [PATCH 1/3] em28xx: give up GPIO register tracking/caching
Date: Mon, 15 Apr 2013 17:11:33 +0300 [thread overview]
Message-ID: <516C0A95.1040101@iki.fi> (raw)
In-Reply-To: <20130415095130.78a5ecd9@redhat.com>
On 04/15/2013 03:51 PM, Mauro Carvalho Chehab wrote:
> Em Sun, 14 Apr 2013 22:35:05 +0200
> Frank Schäfer <fschaefer.oss@googlemail.com> escreveu:
>> I checked the em25xx datasheet (excerpt) and it talks about separate
>> registers for GPIO configuration (unfortunately without explaining their
>> function in detail).
>
> Interesting. There are several old designs (bttv, saa7134,...) that uses
> a separate register for defining the input and the output pins.
That's pretty usual way, likely most common, having separate GPIO
configuration and GPIO value registers. If you has a port of GPIO values
in one register, and you has configured those as 0-3 INPUT and 4-7
OUTPUT, then writing to that register does not make any changes to bits
that are mapped as IN (are just discarded as don't care).
In case a bit I/O (which is not not supported by Kernel) writing to
input register could enable internal pull-up or pull-down resistor :)
IIRC Atmel micro-controllers has such option.
regards
Antti
--
http://palosaari.fi/
next prev parent reply other threads:[~2013-04-15 14:12 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-13 9:48 [PATCH 0/3] em28xx: clean up end extend the GPIO port handling Frank Schäfer
2013-04-13 9:48 ` [PATCH 1/3] em28xx: give up GPIO register tracking/caching Frank Schäfer
2013-04-13 14:41 ` Mauro Carvalho Chehab
2013-04-13 15:33 ` Frank Schäfer
2013-04-13 17:04 ` Mauro Carvalho Chehab
2013-04-13 17:46 ` Frank Schäfer
2013-04-13 18:08 ` Mauro Carvalho Chehab
2013-04-14 20:35 ` Frank Schäfer
2013-04-15 12:51 ` Mauro Carvalho Chehab
2013-04-15 14:11 ` Antti Palosaari [this message]
2013-04-15 16:26 ` Frank Schäfer
2013-04-15 23:01 ` Mauro Carvalho Chehab
2013-04-23 16:58 ` Frank Schäfer
2013-04-13 18:19 ` Frank Schäfer
2013-04-13 18:41 ` Frank Schäfer
2013-04-13 9:48 ` [PATCH 2/3] em28xx: add register defines for em25xx/em276x/7x/8x GPIO registers Frank Schäfer
2013-04-13 9:48 ` [PATCH 3/3] em28xx: add helper function for handling the GPIO registers of newer devices Frank Schäfer
2013-04-13 13:15 ` [PATCH 0/3] em28xx: clean up end extend the GPIO port handling Antti Palosaari
2013-04-13 14:25 ` Mauro Carvalho Chehab
2013-04-13 14:37 ` Antti Palosaari
2013-04-14 1:32 ` Mauro Carvalho Chehab
2013-04-14 19:32 ` Antti Palosaari
2013-04-15 14:40 ` Mauro Carvalho Chehab
2013-04-13 15:30 ` Frank Schäfer
2013-04-13 15:34 ` Devin Heitmueller
2013-04-13 16:21 ` Antti Palosaari
2013-04-13 16:54 ` Devin Heitmueller
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