> Some question on SPI subsystem:
> I really get confused on the structure on the whole system. e.g. the
> platform_data and controller_data in board_info. What are thier
> purposes?
Normally you'd just use platform_data ... which might hold things like
resistance and capacitance settings for that particular board; or details
about which SPI chip variant was present. It gets stored in the struct
device (spi_device->dev) as "platform_data".
Stephen persuaded me to add controller_data too, which is stored in
"struct spi_device". His PXA SPI controller driver uses that for a
structure holding what I'd call DMA tuning information, plus a function
that tweaks the GPIO used for a chipselect. Treat it as readonly.
Controller drivers can have two different kinds of state in each
spi_device: static, and dynamic/runtime. The names used for them
are IMO very confusing (platform_data and controller_data) since
they don't mean the same as those names do in board_info. I'd take
a patch to provide better names for those two. :)
> Also i found that spi_register_board_info is declared as __init, that
> mean i can not register board info as a module, is it because there is
> no 'real' probe on SPI bus?
Combine that lack of probe with the fact that SPI isn't hotpluggable,
and that's pretty much why. You need a table of SPI devices present
on a given board; that boardinfo should be defined just once, in the
relevant arch/arm/mach-imx/board-*.c file. The table never changes,
so there'd be no point in code to change it after board init is done.
(Other than wasting some memory!)
You could also use spi_new_device()/spi_unregister_device() if for some
reason you want to define new boardinfo in a module. You'd need some
out-of-band data to determine what devices are present.
- Dave
p.s. There's a minor refresh to the SPI code coming up soonish; just
fine tuning, and catching up to 2.6.14-git which has removed a
pointless parameter from device_driver.{suspend,resume}() calls.
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