Re: [RFC PATCH 1/2] serial: 8250: Add a notifier chain for driverregistration.

From: David Daney
Date: Thu Mar 17 2011 - 12:42:48 EST

On 03/17/2011 05:18 AM, Alan Cox wrote:
On Wed, 16 Mar 2011 18:26:06 -0700
David Daney<ddaney@xxxxxxxxxxxxxxxxxx> wrote:

The 8250 driver is a bit weird in that in addition to supporting
platform devices, extra devices can be added by calling

The problem is that if we call serial8250_register_port() before the
driver is initialized Bad Things happen (we dereference NULL

There doesn't seem to be a general way to know if a driver has been

I've had a bigger dig into this. I think the correct answer is probably
"always go via platform devices or similar". That *is* the notifier in
the kernel of today. serial8250_register_port ultimately should I think
ultimatly become an internal helper.

That was kind of my thought too. However we have all sorts of things calling serial8250_register_port(). Things like:


The resulting view of the drivers in sysfs is that the little stub code that calls serial8250_register_port() is shown as the driver rather than serial8250. But I suppose that is a matter of aesthetics more than function.

All those 'stub drivers' are relying on the ordering of module_init calls caused indirectly by the Makefile layout. The path of least resistance is your suggestion that I use late_initcall() in my driver stub. I actually tried that before hacking up this patch, but didn't like the idea of relying on *_initcall() ordering being necessary for correct initialization.

David Daney
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