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r: 296910
b: refs/heads/master
c: 3d2ddfd
h: refs/heads/master
v: v3
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Laxman Dewangan authored and Grant Likely committed Mar 5, 2012
1 parent 525d5eb commit bdb32d3
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2 changes: 1 addition & 1 deletion [refs]
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@@ -1,2 +1,2 @@
---
refs/heads/master: 6e2cf6514066cdd5a0844b34760029a5a4870318
refs/heads/master: 3d2ddfdcf05f5f816f829f81858c54827d7be5b4
17 changes: 15 additions & 2 deletions trunk/Documentation/gpio.txt
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Expand Up @@ -302,6 +302,8 @@ where 'flags' is currently defined to specify the following properties:

* GPIOF_INIT_LOW - as output, set initial level to LOW
* GPIOF_INIT_HIGH - as output, set initial level to HIGH
* GPIOF_OPEN_DRAIN - gpio pin is open drain type.
* GPIOF_OPEN_SOURCE - gpio pin is open source type.

since GPIOF_INIT_* are only valid when configured as output, so group valid
combinations as:
Expand All @@ -310,8 +312,19 @@ combinations as:
* GPIOF_OUT_INIT_LOW - configured as output, initial level LOW
* GPIOF_OUT_INIT_HIGH - configured as output, initial level HIGH

In the future, these flags can be extended to support more properties such
as open-drain status.
When setting the flag as GPIOF_OPEN_DRAIN then it will assume that pins is
open drain type. Such pins will not be driven to 1 in output mode. It is
require to connect pull-up on such pins. By enabling this flag, gpio lib will
make the direction to input when it is asked to set value of 1 in output mode
to make the pin HIGH. The pin is make to LOW by driving value 0 in output mode.

When setting the flag as GPIOF_OPEN_SOURCE then it will assume that pins is
open source type. Such pins will not be driven to 0 in output mode. It is
require to connect pull-down on such pin. By enabling this flag, gpio lib will
make the direction to input when it is asked to set value of 0 in output mode
to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode.

In the future, these flags can be extended to support more properties.

Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
introduced to encapsulate all three fields as:
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