dm: Update documentation to include CONFIG_DM... options

Add documentation for the various driver model options that are now
available.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 34 insertions, 10 deletions

diff --git a/doc/driver-model/README.txt b/doc/driver-model/README.txt
index 0278dda4d7..3e2f622657 100644
--- a/doc/driver-model/README.txt
+++ b/doc/driver-model/README.txt
@@ -750,19 +750,43 @@ device pointers, but this is not currently implemented (the root device
 pointer is saved but not made available through the driver model API).
 
 
-Things to punt for later
-------------------------
+SPL Support
+-----------
+
+Driver model can operate in SPL. Its efficient implementation and small code
+size provide for a small overhead which is acceptable for all but the most
+constrained systems.
+
+To enable driver model in SPL, define CONFIG_SPL_DM. You might want to
+consider the following option also. See the main README for more details.
+
+   - CONFIG_SYS_MALLOC_SIMPLE
+   - CONFIG_DM_WARN
+   - CONFIG_DM_DEVICE_REMOVE
+   - CONFIG_DM_STDIO
 
-- SPL support - this will have to be present before many drivers can be
-converted, but it seems like we can add it once we are happy with the
-core implementation.
 
-That is not to say that no thinking has gone into this - in fact there
-is quite a lot there. However, getting these right is non-trivial and
-there is a high cost associated with going down the wrong path.
+Enabling Driver Model
+---------------------
 
-For SPL, it may be possible to fit in a simplified driver model with only
-bind and probe methods, to reduce size.
+Driver model is being brought into U-Boot gradually. As each subsystems gets
+support, a uclass is created and a CONFIG to enable use of driver model for
+that subsystem.
+
+For example CONFIG_DM_SERIAL enables driver model for serial. With that
+defined, the old serial support is not enabled, and your serial driver must
+conform to driver model. With that undefined, the old serial support is
+enabled and driver model is not available for serial. This means that when
+you convert a driver, you must either convert all its boards, or provide for
+the driver to be compiled both with and without driver model (generally this
+is not very hard).
+
+See the main README for full details of the available driver model CONFIG
+options.
+
+
+Things to punt for later
+------------------------
 
 Uclasses are statically numbered at compile time. It would be possible to
 change this to dynamic numbering, but then we would require some sort of