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Commit 3d2ddfdc authored by Laxman Dewangan's avatar Laxman Dewangan Committed by Grant Likely
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Documentation: gpio: Add details of open-drain/source configuration 



Adding details of open drain(open collector) and open source
(open emitter) configuration of the gpio so that client can
set the pin as open drain at the time of gpio request.

Signed-off-by: default avatarLaxman Dewangan <ldewangan@nvidia.com>
Reviwed-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 6e2cf651

Documentation/gpio.txt

+15 −2
Original line number Diff line number Diff line
@@ -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:
@@ -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: