SDIO WiFi Driver Development Questions

Werner Almesberger werner at
Fri Mar 6 04:43:23 CET 2009

dongas wrote:
> And, is the Moko's ar6000 driver in 2.6.29 compatible with both
> firmware 1.3 and 2.0?

The driver we use is only compatible with 2.0. We didn't write our
own driver but are just using Atheros', which a few bug fixes.

> Which version of firmware do you think is better?

We know that 1.3 failed to do SSH. Does this count as a knock-out
criterion ? ;-) After finding that, we went straight to 2.0. So
I don't know if there is more fun in 1.3. Nor do I know if 1.3 is
just one version or if it's a branch.

2.0 has a number of issues, particularly that the firmware likes
to crash itself when encountering malformed management frames.
Seems that someone didn't turn off that -DDEBUG ...

We're in contact with Atheros about resolving these issues, but
so far nothing concrete has emerged.

> Do you mean that with linux sdio stack in kernel 2.6.29, both the SD
> card and SDIO WiFi card can use the same HCD driver?

If you have two identical controllers, there's no reason why they
couldn't use two instances of the same driver.

> Is it that once the SD card works well , the SDIO WiFi card should
> also works well with the same HCD driver?

SDIO needs a few extra things, like the SDIO interrupt. But
"upgrading" an SD driver to SDIO shouldn't be too hard.

> Is s3cmci.c in drivers/mmc/host/ in kernel 2.6.29 a good reference?

It's quite readable, yes. What's missing in s3cmci is handling of
the SDIO interrupt, so we fall back to polling the interrupt in
software, which is a bit inefficient and probably wastes power.

> BTW, do you know if there's some documents talking about the new
> SD/MMC core subsystem with sdio stack intergrated?

Hmm no, haven't heard of one. The code is probably the best
documentation ;-)

Good luck ! :)

- Werner

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