On Sat, Jun 04, 2005 at 11:06:52AM -0400, Alan Stern wrote:
> In spite of the total overall number of changes required, wouldn't it be
> much simpler to have a suite of routines (inlines or macros) like:
>
> get_16, put_16, get_le16, put_le16, get_be16, put_be16
> get_32, put_32, get_le32, put_le32, get_be32, put_be32
> get_64, put_64, get_le64, put_le64, get_be64, put_be64
>
> in short, {get|put}_{|le|be}{16|32|64}
Sorry, no. The architectures that trap on misaligned accesses have to
handle that in the kernel. And even though the implementations
get simpler, a plethoria of interfaces just clutters up the general
device driver API. For that reason alone I wouldn't want it.
The endian conversion (swap) macros are PITA already.
I'll argue the swap API should be simplified to four macros:
cpu_to_le(x), cpu_to_be(x), le_to_cpu(x), be_to_cpu(x)
and force the caller to cast to the right size. switch(sizeof(x)) would
then select the right arch specific variant. I'll figure out how to
pitch this to linux-arch...and then see how far it gets batted back. :^)
> for native, little-endian, and big-endian unaligned accesses? The generic
> definitions are extremely simple and architecture-specific headers could
> easily provide optimized versions.
>
> I realize this doesn't fit in very well with the current state of the API,
> but IMHO it would be a big improvement.
Not really. davem is right that it would clutter up certain parts
of the code (e.g. networking stack).
Don't forget all the above is a NOP on 90% (x86) of the computers.
I'm annoyed that certain performance sensitive paths (e.g. TCP/IP) don't
use macros to access unaligned data. It affects my work (ia64)
and pet (parisc) architectures. But that's how it is and I don't
see it changing anytime in the near future.
thanks for thinking about it,
grant
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