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

[David Brownell <david-b@pacbell.net>]

On Thursday 08 June 2006 6:25 pm, Nicolas Pitre wrote:
> 
> You are both saying the same thing so far.

Hey, violent agreement is half the fun!  :)


> > 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.

I see your point.  Yes, this is arguable ... there are multiple principles
that can be traded off against each other.


For example, "by default, make design choices that save memory" (what I was
using) versus:

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

For a kernel without CONFIG_MODULES, that's pure wasted space.  Why bother?
Those are devices that "can't be present", so that's one of the cases where
that "ignore the driver config" policy will indeed register such devices.

Similarly, when the driver's not yet written, it can make trouble to try
sticking its config into the device tree ... it's very easy to get wrong!


It's clear to me there are some cases where software config will reasonably
be a subset of the hardware config.  Likewise, that memory usage should be
one of the factors considered when making design tradeoffs.

- Dave