On Sun, Aug 10, 2014 at 2:59 AM, Simon Glass sjg@chromium.org wrote:
Hi,
On 14 July 2014 18:56, Simon Glass sjg@chromium.org wrote:
Up until now driver model has not been used for any type of bus. Buses have some unique properties and needs, so we cannot claim that driver model can cover all the common cases unless we have converted a bus over to driver model.
SPI is a reasonable choice for this next step. It has a fairly simple API and not too many dependencies. The main one is SPI flash so we may as well convert that also. Since the boards I test with have cros_ec I have also included that, for SPI only.
The technique used is make use of driver model's supported data structures to hold information currently kept by each subsystem in a private data structure. Since 'struct spi_slave' relates to the slave device on the bus it is stored in the 'parent' data with each child device of the bus. Since 'struct spi_flash' is a standard interface used for each SPI flash driver, it is stored in the SPI FLash uclass's private data for each device.
New defines are created to enable driver model for each subsystem. These are:
CONFIG_DM_SPI CONFIG_DM_SPI_FLASH CONFIG_DM_CROS_EC
This allows us to move some boards and drivers to driver model, while leaving others behind. A 'big bang' conversion of everything to driver model, event at a subsystem level, is never going to work.
On the other hand, we change the driver at the same time as the CONFIG option is enabled. Keeping both version of the driver around involves a flock of #ifdefs, the benefit of which is not apparent to me, since the old code is removed anyway.
There is some cost in changing the uclass interface after it is created, so if you have limited time, please spend it reviewing the uclass interfaces in spi.h and spi_flash.h. These need to be supported by each driver, so changing them later may involve changing multiple drivers.
To help with conversion of SPI drivers to driver model, documentation is provided which takes the happy camper through the process with an example.
As always, driver model patches are available at u-boot-dm.git branch 'working'.
Note: This series is not fully ready - e.g. some header files are missing comments. But I wanted to get it out for review early since some SPI work is ongoing which might depend on it.
Are there any comments on this series please? I'd like to apply these to dm/master early next week, excluding the exynos ones.
I will be busy in next full week, give me 2 more weeks. Probably I will give my comments on next to next weekend.
thanks!