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add gpio.h for generic GPIO-related definitions 

This adds /src/include/gpio.h which currently contains generic GPIO
enums for type (in/out/alt) and 3-state logic.

The header was originally written for another FOSS project
(code.google.com/p/mosys) and thus the BSD license.

Change-Id: Id1dff69169e8b1ec372107737d356b0fa0d80498
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/2265
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
This commit is contained in:
David Hendricks 2013-02-02 16:57:11 -08:00 committed by Ronald G. Minnich
parent 10883945dc
commit d58ba2add4
1 changed files with 63 additions and 0 deletions
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/*
* Copyright 2012, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef GPIO_H
#define GPIO_H
enum gpio_types {
GPIO_IN,
GPIO_OUT,
GPIO_ALT, /* catch-all for alternate functions */
};
/*
* Many-value logic (3 states). This can be used for inputs whereby presence
* of external pull-up or pull-down resistors can be added to overcome internal
* pull-ups/pull-downs and force a single value.
*
* Thus, external pull resistors can force a 0 or 1 and if the value changes
* along with internal pull-up/down enable then the input is floating.
*
* Vpd | Vpu | MVL
* -----------------
* 0 | 0 | 0
* -----------------
* 0 | 1 | Z <-- floating input will follow internal pull up/down
* -----------------
* 1 | 1 | 1
*/
enum mvl3 {
LOGIC_0,
LOGIC_1,
LOGIC_Z, /* high impedence / tri-stated / floating */
};
#endif /* GPIO_H */