Re: [PATCH] sdio: add MMC_CAP_VDD_165_195 host capability

[Pierre Ossman <pierre@ossman.eu>]

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On Mon, 28 Sep 2009 19:25:48 -0700
Philip Langdale <philipl@overt.org> wrote:

> 
> Hi David,
> 
> Ok, that sounds reasonable, but my concern is a controller that
> publishes support for MMC_VDD_165_195 for mmc cards but doesn't
> claim support for SDIO cards - particularly considering the
> signalling implications you mentioned. Now, maybe you don't see
> this happening in the wild, but it seems to me that it has to
> be possible. It seems that to guard against this, you'd need a
> host cap that says "165_195 for SD" and if it's not present,
> mask it out of the OCR when dealing with SD/IO cards.
> 
> Am I being too paranoid?
> 

There is no way the vendor of the SD controller can know what this bit
means to the vendor of the SD/SDIO card as it is undefined. I'm afraid
I see no safe way of supporting this bit. The only thing we can do is
interpret it as being the same as the MMC bit, but then only with an
opt-in configuration as we might be killing hardware with this.

Rgds
-- 
     -- Pierre Ossman

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