Re: [PATCH] i2c: tegra: Add i2c support

[Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>]

On Sun, Feb 20, 2011 at 3:38 PM, Ben Dooks <ben-i2c-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org> wrote:
<snip>

>> > you know, there's a readsl() function that does this.
>> I think readsl can't handle the possibly unaligned buf pointer.
>
> it does. see arch/arm/lib/io-writesl.S for proof.
You're right, I traced the wrong definition of readsl/writesl

>> > this whole function gives me the creeps, is there any reason why
>> > we can't use the readsl or similar functions for this?
>> Same here - readsl can't handle the alignment requirements, readsb
>> can't  handle the required 32 bit register read, and the bytes in the
>> same word but after the end buf may not be part of buf, so byte writes
>> to buf are required.
>
> You'll find it can, too. arch/arm/lib/io-readsl.S.
I still think readsl doesn't work here.  It may need to read 7 bytes,
requiring 2 calls to readl, but 1 word write and 3 byte writes to buf.
 Using readsl for the whole buffer would overwrite the 8th byte.  I
can use readsl for the main loop, but I will still need to write the
last 1-3 bytes separately.  I could use readl and memcpy to do the
last writes.