linux-kernel - Re: [PATCH 27/30] staging/vme: rework the bus model

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Date:	Wed, 27 Oct 2010 11:40:46 -0400
From:	"Emilio G. Cota" <cota@...ap.org>
To:	Martyn Welch <martyn.welch@...com>
Cc:	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>,
	Juan David Gonzalez Cobas <david.cobas@...il.com>
Subject: Re: [PATCH 27/30] staging/vme: rework the bus model

On Wed, Oct 27, 2010 at 10:16:21 +0100, Martyn Welch wrote:
> On 26/10/10 02:02, Emilio G. Cota wrote:
> > On Mon, Oct 25, 2010 at 12:24:38 +0100, Martyn Welch wrote:
> >> On 23/10/10 00:27, Emilio G. Cota wrote:
> >>>> * installing drivers even before the bridges they need are present
> >>>>   seems counter-intuitive and wrong.
> >>
> >> There are plenty of instances where a driver can be loaded before the
> >> bus is probed or a device is even present. When the bus become
> >> available, the probe routine will be run.
> > 
> > That would be acceptable if and only if no other alternative was available.
> > 
> > It doesn't make any sense to constrain ourselves to installing
> > drivers only BEFORE loading bridge drivers.
> > 
> 
> I have no idea what your doing, but that simply isn't the case. Your
> right - that really would not make any sense, however I'm happily
> loading the bridge drivers before any VME device drivers here.

/me scratches his head and goes back the code again.

I see, so after calling driver_register() the core will initiate
the binding--I was wrongly thinking that binding would only happen
after registering a device with device_register().

In fact I claimed this from what I remembered from the code. But
this was months ago, and my memory is highly unreliable.
Sorry about that :(

However I just remembered something, related to the unique slot
numbers. Let me know if this is correct or not, but in fact
I think this is what triggered me to write a new model.

Imagine the following situation:

- insmod vme_driver1.ko bus=0,0,0 slot=1,2,3

Then two days after I want to install another driver:

- insmod vme_driver2.ko bus=0,0,0 slot=X,Y,Z

Now X,Y,Z cannot be in (1,2,3), because those are understood
as physical slots, even if they're not (this is not VME64x)

So, anytime I need to install a device, I must know the slot
numbers of all other devices--even though there's no
physical meaning to it!

In the model I proposed device id's ("slots") are unique
to each driver.

Does this make sense?

Cheers

		Emilio
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