[PATCH 3/4] Documentation: bootchooser: add information about slots_locked

[Lars Schmidt <l.schmidt@pengutronix.de>]

The new slots_locked variable does have influence on
remaining_attempt counter.

Signed-off-by: Lars Schmidt <l.schmidt@pengutronix.de>
---
 Documentation/user/bootchooser.rst | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/Documentation/user/bootchooser.rst b/Documentation/user/bootchooser.rst
index 351e1d14e1..306443270a 100644
--- a/Documentation/user/bootchooser.rst
+++ b/Documentation/user/bootchooser.rst
@@ -77,6 +77,16 @@ no remaining attempts left.
 To prevent ending up in an unbootable system after a number of failed boot
 attempts, there is also a built-in mechanism to reset the counters to their defaults,
 controlled by the ``global.bootchooser.reset_attempts`` variable.
+Alternatively, counting down the remaining attempts can be disabled by
+locking the bootchooser slots.
+This is done by defining a (32-bit) ``slots_locked`` variable in the
+bootstate and setting its value to ``1`` (usually from userspace).
+
+The variable affects all slots, is optional and its absence is
+interpreted as ``0``, meaning that attempts are decremented normally.
+
+The ``slots_locked`` value does not influence the decision on which slot
+to boot if any, only whether to decrement the attempts when booting.
 
 If ``global.bootchooser.retry`` is enabled (set to ``1``), the bootchooser
 algorithm will iterate through all valid boot targets (and decrease their
@@ -107,6 +117,19 @@ on the :ref:`reset reason <reset_reason>` (i.e. != WDG) using the
 This will reset the ``remaining_attempts`` counter of the *last chosen* slot to
 its default value (``reset_attempts``).
 
+Another option is to use ``slots_locked``.
+Normally this should be controlled from Linux userspace using the *barebox-state* tool, i.e.::
+
+  barebox-state -s  bootstate.slots_locked=1
+
+It can also be locked via the :ref:`bootchooser command <command_bootchooser>`::
+
+  bootchooser -l
+
+or unlocked::
+
+  bootchooser -L
+
 
 .. _dt-utils: https://git.pengutronix.de/cgit/tools/dt-utils
 
-- 
2.39.5