On Saturday 15 February 2014 12:27:33 Russell King - ARM Linux wrote:

On Sat, Feb 15, 2014 at 01:18:02PM +0100, Arnd Bergmann wrote:

quoted

If a wlan adapter has both SPI and SDIO front-ends, the external
dependencies (reset, clock, voltage, ...) will be the same, and
from the kernel perspective the main difference is that SPI cannot
be probed at all, while SDIO can be probed as long as the device
is powered on already.

Remember that MMC/SD/SDIO cards can be driven by either a MMC host
interface, or a SPI interface.  Both are probe-able.

I knew about MMC/SD cards being required to understand simple SPI,
I wasn't sure about SDIO. My understanding however is that you
have to use the mmc_spi host driver to actually use MMC/SD devices
as a block device, and that requires having either a DT description
for the host or an spi_board_info, which I would not consider
discoverable.

For spi-mode SDIO devices I'm assuming it's similar, except that
you'd describe the actual SDIO device in the board info rather than
create a fake SDIO controller. Still not discoverable unless I'm
missing your point.

	Arnd