Re: __LITTLE_ENDIAN vs. __LITTLE_ENDIAN_BITFIELD

[Timur Tabi <timur@freescale.com>]

Jan Engelhardt wrote:

> Bit representation is left to the CPU, so 1 << 1 will always be 2,
> regardless of whether the byte, when sent out to the network,
> is 01000000 or 00000010. Endianess becomes important as soon
> as the packet is on the network, of course.

Well yes, that's why I'm asking.  I'm not concerned about data from just the 
CPU's perspective.

I'm writing a driver that talks to hardware that has a shift register.  The 
register can be shifted either left or right, so all the bits obviously have 
to be in order, but it can be either order.

What I want to do is to have the driver detect when byte-endianness doesn't 
match bit-endianness when it writes the the word to a memory-mapped device.  I 
think I can do that like this:

#if (defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN_BITFIELD)) || 
(defined(BIG_ENDIAN) && defined(LITTLE_ENDIAN_BITFIELD))
#error "This CPU architecture is not supported"
#endif

-- 
Timur Tabi
Linux Kernel Developer @ Freescale