Re: SDIO card support in Linux

[Pierre Ossman]

Ian Stirling wrote:
>>
>> 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?

Yes, no. :)

> 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.
>

The problem is that there is no "king-of-the-hill" mechanism in the SDIO
init sequence (like there is in SD mem). The protocol assumes that the
desired card always receives the command.

Rgds
Pierre

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