Re: MMC Driver RFC
From: Ian Molton
Date: Wed Jan 12 2005 - 18:43:02 EST
Russell King wrote:
That depends whether the hardware already provides 0.5s of debounce
already. Some people do, some people don't. This is why it needs to
be left to the implementation and not a core issue.
Agreed. IIRC my toshiba PDAs *dont* provide a delay. OTOH they also
provide *two* ways of detecting card presence...
2. Card Initialisation Problems
Different cards behave differently. I suspect you have yet another
quirky card.
What is the policy on handling this? Pin the error down, then see what can
be done about it? I'll just have to move delays about until I find the one
that helps guess.
I was wondering if there was some kind of timing specification somewhere as
all these cards seem to work fine under other operating systems...
That's probably the official MMC specification from the MMC forum. Us
mere open source developers don't have access to such costly specs, so
we have to make do with the specs released by card manufacturers which
do go into the protocol sufficiently deeply.
Unfortunately, such specs only cover MMC cards and not SD cards.
ISTR seeing a SD card doc at some point
I have no idea - and that's the big problem. We just don't know
what the situation is with SD.
Maybe now that it's more wildly known that there's SD support available
from handhelds.org, maybe (if the SD forum are reading lkml) we'll see
some reaction. Let's just hope it's positive.
Well I *know* I never saw the specs from the SD forum. I hacve never
reverse engineered a SDHC core driver either (I have reverse engineered
a chip driver but it contained no SD *protocol* information.
as such my code should be 100% safe to commit to the kernel.
PS. Richard - I am here - hope you receive this!
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