Re: [linux-usb-devel] [PATCH] limit power budget on spitz

[Nicolas Pitre]

On Thu, 8 Jun 2006, David Brownell wrote:

> On Thursday 08 June 2006 2:49 pm, Richard Purdie wrote:
> > 
> > > One additional nuance:  if
> > > the kernel doesn't have that driver configured, that's another reason not
> > > to bother registering its device.
> > 
> > This is where you start to add ugly ifdefs and generally start making
> > the code look horrible. The device model separated the drivers and the
> > devices to deal with this issue as I see it. 
> 
> Enumeration is a separate issue.  You wouldn't argue that every potential
> PCI or USB device must get registered, right?  Only the ones that are
> actually _present_ get registered.

You are both saying the same thing so far.

> But here you argue that platform bus should not work that same way ... it
> should register devices that can't be present.  If nothing else, that's
> an inconsistent aproach.

That's not what Richard is saying.

He replied to your assertion where you said: "if the kernel doesn't have 
that driver configured, that's another reason not to bother registering 
its device" to which he disagreed, and I disagree too.

> Plus, consider the common situation that a given pin could potentially
> be used with several different devices.  On a given board, only one of
> those devices will be wired up.  It's counterproductive to register any
> of the others ... error prone, waste-of-kernel-address-space, etc.

No one disagreed with that AFAICS.

> > Generally I'd say its 
> > cleaner just to let the device register, then if a module comes along at
> > some later point, the device is there for it.
> 
> Whether the device is there or not is a hardware issue.  Board schematics
> will show which devices are relevant ... registering any others is just
> wastage.

But you originally talked about _driver_ configuration dictating if a 
_device_ should be registered or not.

The _device_ should indeed be registered based on _hardware_ config, not 
_driver_ config.


Nicolas
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