Some platforms use tertiary interpretation of GPIO input state to
increase number of distinct values represented by a limited number of
GPIOs. The three states are
- external pull down (interpreted as 0)
- external pull up (1)
- not connected (2)
This has been required by Nvidia devices so far, but Exynos and
Ipq8086 platforms need this too.
This patch moves the function reading the tertiary state into the
library and exposes the necessary GPIO API functions in a new include
file. The functions are still supposed to be provided by platform
specific modules.
The function interpreting the GPIO states has been modified to allow
to interpret the state either as a true tertiary number or as a set
two bit fields.
Since linker garbage collection is not happening when building x86
targets, a new configuration option is being added to include the new
module only when needed.
BUG=chrome-os-partner:30489
TEST=verified that nyan_big still reports proper revision ID.
Change-Id: I243c9f43c82bd4a41de2154bbdbd07df0a241046
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/209673
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
c79ef1c545