[PATCH v2 02/10] pwm: Allow chips to support multiple PWMs.

[Russell King - ARM Linux]

On Wed, Feb 08, 2012 at 09:15:08AM +0100, Thierry Reding wrote:
> * Ryan Mallon wrote:
> > On 07/02/12 02:19, Thierry Reding wrote:
> > > The total maximum number of PWM devices is currently fixed to 64, but
> > > can easily be made configurable via Kconfig.
> > 
> > It would be better to make the code handle arbitrary numbers of PWMs. A
> > Kconfig knob becomes annoying when you have more than one platform
> > configured into the kernel.
> 
> AFAICT handling an arbitrary number of PWMs will only be possible once we get
> rid of the global namespace and therefore should be postponed for later. I
> may be wrong, though, so if anybody can point me in the right direction I'm
> perfectly happy to change that in this series.

One solution would be to look at how genirq handles this.  Eg, it uses a
radix tree to store the irqdescs rather than an array, and a bitmap
showing which global numbers are allocated.