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>

README

@@ -623,6 +623,120 @@ The following options need to be configured:
 		exists, unlike the similar options in the Linux kernel. Do not
 		set these options unless they apply!
 
+- Driver Model
+		Driver model is a new framework for devices in U-Boot
+		introduced in early 2014. U-Boot is being progressively
+		moved over to this. It offers a consistent device structure,
+		supports grouping devices into classes and has built-in
+		handling of platform data and device tree.
+
+		To enable transition to driver model in a relatively
+		painful fashion, each subsystem can be independently
+		switched between the legacy/ad-hoc approach and the new
+		driver model using the options below. Also, many uclass
+		interfaces include compatibility features which may be
+		removed once the conversion of that subsystem is complete.
+		As a result, the API provided by the subsystem may in fact
+		not change with driver model.
+
+		See doc/driver-model/README.txt for more information.
+
+		CONFIG_DM
+
+		Enable driver model. This brings in the core support,
+		including scanning of platform data on start-up. If
+		CONFIG_OF_CONTROL is enabled, the device tree will be
+		scanned also when available.
+
+		CONFIG_CMD_DM
+
+		Enable driver model test commands. These allow you to print
+		out the driver model tree and the uclasses.
+
+		CONFIG_DM_DEMO
+
+		Enable some demo devices and the 'demo' command. These are
+		really only useful for playing around while trying to
+		understand driver model in sandbox.
+
+		CONFIG_SPL_DM
+
+		Enable driver model in SPL. You will need to provide a
+		suitable malloc() implementation. If you are not using the
+		full malloc() enabled by CONFIG_SYS_SPL_MALLOC_START,
+		consider using CONFIG_SYS_MALLOC_SIMPLE. In that case you
+		must provide CONFIG_SYS_MALLOC_F_LEN to set the size.
+		In most cases driver model will only allocate a few uclasses
+		and devices in SPL, so 1KB should be enable. See
+		CONFIG_SYS_MALLOC_F_LEN for more details on how to enable
+		it.
+
+		CONFIG_DM_SERIAL
+
+		Enable driver model for serial. This replaces
+		drivers/serial/serial.c with the serial uclass, which
+		implements serial_putc() etc. The uclass interface is
+		defined in include/serial.h.
+
+		CONFIG_DM_GPIO
+
+		Enable driver model for GPIO access. The standard GPIO
+		interface (gpio_get_value(), etc.) is then implemented by
+		the GPIO uclass. Drivers provide methods to query the
+		particular GPIOs that they provide. The uclass interface
+		is defined in include/asm-generic/gpio.h.
+
+		CONFIG_DM_SPI
+
+		Enable driver model for SPI. The SPI slave interface
+		(spi_setup_slave(), spi_xfer(), etc.) is then implemented by
+		the SPI uclass. Drivers provide methods to access the SPI
+		buses that they control. The uclass interface is defined in
+		include/spi.h. The existing spi_slave structure is attached
+		as 'parent data' to every slave on each bus. Slaves
+		typically use driver-private data instead of extending the
+		spi_slave structure.
+
+		CONFIG_DM_SPI_FLASH
+
+		Enable driver model for SPI flash. This SPI flash interface
+		(spi_flash_probe(), spi_flash_write(), etc.) is then
+		implemented by the SPI flash uclass. There is one standard
+		SPI flash driver which knows how to probe most chips
+		supported by U-Boot. The uclass interface is defined in
+		include/spi_flash.h, but is currently fully compatible
+		with the old interface to avoid confusion and duplication
+		during the transition parent. SPI and SPI flash must be
+		enabled together (it is not possible to use driver model
+		for one and not the other).
+
+		CONFIG_DM_CROS_EC
+
+		Enable driver model for the Chrome OS EC interface. This
+		allows the cros_ec SPI driver to operate with CONFIG_DM_SPI
+		but otherwise makes few changes. Since cros_ec also supports
+		I2C and LPC (which don't support driver model yet), a full
+		conversion is not yet possible.
+
+
+		** Code size options: The following options are enabled by
+		default except in SPL. Enable them explicitly to get these
+		features in SPL.
+
+		CONFIG_DM_WARN
+
+		Enable the dm_warn() function. This can use up quite a bit
+		of space for its strings.
+
+		CONFIG_DM_STDIO
+
+		Enable registering a serial device with the stdio library.
+
+		CONFIG_DM_DEVICE_REMOVE
+
+		Enable removing of devices.
+
+
 - Linux Kernel Interface:
 		CONFIG_CLOCKS_IN_MHZ
 
@@ -3881,6 +3995,11 @@ Configuration Settings:
 		Pre-relocation malloc() is only supported on ARM and sandbox
 		at present but is fairly easy to enable for other archs.
 
+- CONFIG_SYS_MALLOC_SIMPLE
+		Provides a simple and small malloc() and calloc() for those
+		boards which do not use the full malloc in SPL (which is
+		enabled with CONFIG_SYS_SPL_MALLOC_START).
+
 - CONFIG_SYS_BOOTM_LEN:
 		Normally compressed uImages are limited to an
 		uncompressed size of 8 MBytes. If this is not enough,

doc/driver-model/README.txt

@@ -750,20 +750,44 @@ device pointers, but this is not currently implemented (the root device
 pointer is saved but not made available through the driver model API).
 
 
+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
+
+
+Enabling Driver Model
+---------------------
+
+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
 ------------------------
 
-- 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.
-
-For SPL, it may be possible to fit in a simplified driver model with only
-bind and probe methods, to reduce size.
-
 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
 lookup service, perhaps searching by name. This is slightly less efficient