gpio-naming: clarify button definition
Fixes openbmc/docs#72.
There was some question if buttons are strictly input or could also be
used in cases where the BMC emulates a physical button. Clarify the
button section here to indicate that *-button gpios are strictly input.
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I4f23dcb351e83af657f4af6bbf641c1e9033a007
diff --git a/designs/device-tree-gpio-naming.md b/designs/device-tree-gpio-naming.md
index 0cec8c4..94d1a5a 100644
--- a/designs/device-tree-gpio-naming.md
+++ b/designs/device-tree-gpio-naming.md
@@ -50,6 +50,12 @@
### Buttons
Pattern: `*-button`
+Buttons should always be considered 'input' to the BMC. There may be cases
+where BMC-less machines use a button to trigger system behavior and in a
+BMC-managed system this signal is emulated by the BMC (as output). These
+should not be considered a button in this document but enumerated as another
+signal type.
+
#### power-button
### Host Ready