On Sat, Jun 19, 2010 at 02:12:21AM +0100, Mark Brown wrote:
> On Sat, Jun 19, 2010 at 08:24:36AM +1000, Stuart Longland wrote:
> > + /* Page 1 */
> > + if (page == 1) {
> > + if (reg <= 4)
> > + return 1;
>
> I can't help but think that this'd be more legible with switch ()
> statements (GCC has an extension for ranges in switch statements which
> you could use).
I gave this some further thought... I'm not certain that a switch
statement is going to be much clearer. There are two ways I can tackle
this.
One is to go on a page-by-page basis, which is how I do it using the if
statements. Here; I define my ranges so that I start from the very
end... anything beyond page 70 is invalid ... voila, I eliminate those
early on. A number of pages have a similar register pattern, and so I
make use of nested if statements to explain this. The if block for
pages following always use the block before to define the upper,
non-inclusive bound.
The register tests start from register 0. I could perhaps reverse the
outer ifs to start at page 0 and work forwards too... but I instead work
backwards from page 70.
I exit the function as early as possible to skip unneeded checks, as
soon as I know a range is valid or not, I return 1 or 0. Perhaps the 1
or 0 could be made clearer (a couple of #defines maybe?) but to me, it
looks fairly clear.
I could use switch statements to replace some or all of the if
statements. There'd be a small benefit I suppose in making the outer if
statements a switch, but little anywhere else from what I can see.
The other way is that I ignore pages completely; and use the
AIC3204_PGREG macro to define ranges of absolute register addresses.
This may have a small benefit in speed since these are compiled in... as
opposed to runtime masking/shifting, but I don't see that being much
clearer either. I'd still come to a case statement, then return.
This is a function largely intended for debugging, in fact, I'm thinking
I should probably wrap it in #ifdef CONFIG_DEBUG_FS, since the function
isn't called unless debugfs is enabled. So I'm not certain that
performance is worth chasing here given the intended purpose -- it's not
something that's called all the time, nor something that will be used in
a production environment.
That's my thoughts on the issue, perhaps naïve, but I'm not sure
there's any real gain in refactoring this.
--
Stuart Longland (aka Redhatter, VK4MSL) .'''.
Gentoo Linux/MIPS Cobalt and Docs Developer '.'` :
. . . . . . . . . . . . . . . . . . . . . . .'.'
http://dev.gentoo.org/~redhatter :.'
I haven't lost my mind...
...it's backed up on a tape somewhere.
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