regulator: Add some brief design documentation
Provide some brief documentation of some of the design decisions that
are made by the regulator API.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>
diff --git a/Documentation/power/regulator/design.txt b/Documentation/power/regulator/design.txt
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+Regulator API design notes
+==========================
+
+This document provides a brief, partially structured, overview of some
+of the design considerations which impact the regulator API design.
+
+Safety
+------
+
+ - Errors in regulator configuration can have very serious consequences
+ for the system, potentially including lasting hardware damage.
+ - It is not possible to automatically determine the power confugration
+ of the system - software-equivalent variants of the same chip may
+ have different power requirments, and not all components with power
+ requirements are visible to software.
+
+ => The API should make no changes to the hardware state unless it has
+ specific knowledge that these changes are safe to do perform on
+ this particular system.
+
+Consumer use cases
+------------------
+
+ - The overwhelming majority of devices in a system will have no
+ requirement to do any runtime configuration of their power beyond
+ being able to turn it on or off.
+
+ - Many of the power supplies in the system will be shared between many
+ different consumers.
+
+ => The consumer API should be structured so that these use cases are
+ very easy to handle and so that consumers will work with shared
+ supplies without any additional effort.