Re: __LITTLE_ENDIAN vs. __LITTLE_ENDIAN_BITFIELD

[Timur Tabi <timur@freescale.com>]

Lennart Sorensen wrote:

>> You're talking about byte endian.  I'm talking about bit endian -- the 
>> order of bits within a byte.  Software cannot know what the bit endian is, 
>> but external devices that have memory-mapped registers can know.
> 
> The guy wiring up the hardware should connect the wires correctly.

I'm sure they're correct, my problem is that how can my driver know what they are?

> Doesn't the bus usually have some definition of bit order which the
> device would have to adhere to?  After all there must be address lines
> somewhere.

I was hoping that there would be some compile-time constant I could check that 
would give me this information.

> Does this perhaps offer anything useful?
> http://www.linuxjournal.com/article/6788

Yeah, I read that article some time ago when trying to diagnose the problem I 
was seeing.  It does explain the point I'm trying to make.  We have a device 
that's used on two product lines: one ARM-based, and one PowerPC.  The ARM is 
little-endian, and the PowerPC is big-endian.  The device can support 
little-endian or big-endian data, as long as the bit-order matches the byte-order.

For now, I'm going to have to assume that they do match.

-- 
Timur Tabi
Linux Kernel Developer @ Freescale