Re: [PATCH 4/7] mmc: at91_mci: add multiwrite switch

[Pierre Ossman]

On Sun, 1 Jun 2008 15:42:52 +0100
Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote:

> If Pierre wants to remove the MULTIWRITE flag, I'd like to hear his
> solution for the pxamci driver, where the only way to ascertain how
> many bytes were transmitted may be to walk the SG list comparing the
> DMA pointer with what was in the hardware DMA engine at the time.
> Maybe.

You set bytes_xfered to 0. As mentioned in my previous mail, I had a
chat with Jens about this and upper layers can only expect to get the
lower bound in how many bytes were written. Other hardware/drivers
already behaves like this so there is no point in crippling the MMC
layer in an effort to give nicer guarantees.

This is why I asked people to audit their drivers to make sure it's
the lower bound that's returned, but I've not received much in the way
of replies.

Rgds
Pierre

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