Subject: Re: [GIT PULL] ARM: SoC fixes for v5.10, part 3

From: Russell King - ARM Linux admin <[email-masked]>
Date: Mon, 30 Nov 2020 22:54:59 +0000

On Mon, Nov 30, 2020 at 10:22:58AM -0800, Linus Torvalds wrote:
> > I guess the question is: why is static assignment of numbers not an
> > acceptable solution to the problem?  It gives us the desired fixed
> > numbers and automatically avoids all weird probe ordering / dependency
> > problems.
> 
> I think that if this had been done originally, it would probably be fine.

It was not done originally, because the original structure of the MMC
bus was:

host controller ---+--- card 1
                   +--- card 2
		   +--- card 3
		   ...

So one host controller could be connected to multiple different cards,
and the bus has a way to detect each card individually. This means we
had no idea how many cards would be connected to any one controller,
and it was entirely sensible to allocate MMC block devices in the order
we discovered the cards.

The SD specification, this became limited to just one card per
controller to allow for faster speeds.

-- 
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