Re: [PATCH] add new DMA_ADDR_T_SIZE define

[James Bottomley]

> 3. use run-time checks all over the place, of the 
> "sizeof(dma_addr_t)==sizeof(u64)" kind, which adds unnecessary
> overhead to 
> all platforms.

Actually, these aren't technically run time checks.  Although the cpp
can't be used for sizeof(), the compiler (at least gcc) does seem to
have enough sense to optimise away if(..) branches it has enough
information to know won't be taken at compile time.

As long as this optimisation works, I think the if(sizeof(..)) checks
are fine for this.

James