Re: SDIO card support in Linux

[Ian Stirling <ian.stirling@mauve.plus.com>]

Pierre Ossman wrote:
> madhu chikkature wrote:
> > Hi,
> >
> > This is regarding the discussion going on in the list about the
> > support of SDIO cards in Linux. I read some discussion happening to
> > support SDIO cards using the existing Linux MMC core but I could not
> > figure out what would be the direction the community to support the
> > SDIO cards.
<snip>
> > With this, is it a fissible solution to have the MMC core do the
> > initialization part of the card by having the CMD sequence for SDIO
> > card (CMD5 and CMD3) in the mmc_setup sequence and maintain the SDIO
> > card list along with MMC/SD?
>
> SD mandates a star topology (just a single card per bus), so we'll just
> force a single card into the list. SD memory cards can actually work on
> a shared bus, SDIO can not. It's not a big problem in practice though.

Is this true in SD-1 bit mode, or SPI?
I see nothing on a quick read-through of the abbreviated SDIO spec 
precluding  this.
Of course, it'd mean wire-or'd interrupt lines.

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