[Xen-devel] Re: [PATCH 01/15] [swiotlb] fix: Update 'setup_io_tlb_npages' to accept both arguments in either order.

[Chris Wright <chrisw@xxxxxxxxxxxx>]

* Konrad Rzeszutek Wilk (konrad.wilk@xxxxxxxxxx) wrote:
> On Thu, Jan 14, 2010 at 05:22:13PM -0800, Chris Wright wrote:
> > * Konrad Rzeszutek Wilk (konrad.wilk@xxxxxxxxxx) wrote:
> > > Before this patch, if you specified 'swiotlb=force,1024' it would
> > > ignore both arguments. This fixes it and allows the user specify it
> > > in any order (or none at all).
> > > 
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > 
> > Having only one substring of digits makes allowing arbitrary order
> > less useful if more options get added (as in foo,bar,1024,baz,force
> > would make more sense as foo,bar,nslabs=1024,baz,force).  Do you
> > think this one is really needed?  If so, be useful to update
> 
> I got caught a couple of times where I needed to provide both arguments
> and could not figure out why it did not work. Switching the arguments
> around fixed it. Thought that it might make sense to remove this
> potential trap from other folks by this patch.
> 
> Your point about more options got me thinking about the overflow buffer.
> I could also provide an over-ride for that, maybe:
> 
> "swiotlb=force,overflow=32,slabs=1024"

Right, in which case would the is_digit() check remain ahead of the loop
to protect the "legacy" format (swiotlb=1024,force), forcing mixing like
you did to the new format (swiotlb=force,slabs=1024 or
swiotlb=slabs=1024,force)?

> (Not sure about the syntax?)
> 
> > Documentation/kernel-parameters.txt which is slightly out of date now.
> 
> Oh, good catch. Will roll the patch for that file as well.

thanks,
-chris

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