[PATCH v4 4/4] power: supply: core: document measurement points

[MichaÅ MirosÅaw]

Document used prefixes for input/output/storage voltages and currents.

Signed-off-by: MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>
---
 Documentation/power/power_supply_class.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/power/power_supply_class.rst b/Documentation/power/power_supply_class.rst
index 7b8c42f8b1de..c41b25aaa755 100644
--- a/Documentation/power/power_supply_class.rst
+++ b/Documentation/power/power_supply_class.rst
@@ -28,6 +28,12 @@ indication (including whether to use it at all) are fully controllable by
 user and/or specific machine defaults, per design principles of LED
 framework).
 
+There are three defined points of measurement for the benefit of mobile and
+UPS-like power supplies: INPUT (external power source), OUTPUT (power output
+from the module), and unmarked (power flowing to/from a storage element,
+eg. battery). Battery is viewed as a power source, so current flowing to
+the battery (charging it) is shown negative.
+
 
 Attributes/properties
 ~~~~~~~~~~~~~~~~~~~~~
-- 
2.20.1