Re: [PATCH] add new DMA_ADDR_T_SIZE define

["David S. Miller" <davem@redhat.com>]

On Wed, 2003-02-19 at 08:26, Ion Badulescu wrote:
> This patch adds a new preprocessor define called DMA_ADDR_T_SIZE for all 
> architectures, for the benefit of those drivers who care about its size 
> (and yes, starfire is one of them).

I don't think you are making things any better by adding
a new ifdef to all the drivers.

> 2. always cast it to u64, which adds unnecessary overhead to 32-bit 
> platforms.

Not to HIGHMEM ones.  And frankly, trying to super-optimize a driver
because it has two different descriptor format is a mess you as a driver
author choose to get involved in.

Nearly all cards today are 64-bit DMA address descriptors only.
So if anything, this new ifdef will get less and less used over
time.

> 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.

The compiler optimizes this completely away, it becomes
a compile time test and the unused code block and the test
never make it into the assembler.

So this argument is bogus, as is the define.