linux-kernel - Re: [RFC PATCH 1/2] serial: 8250: Add a notifier chain for driver registration.

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Message-ID: <4D826B52.3060304@caviumnetworks.com>
Date:	Thu, 17 Mar 2011 13:13:06 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-serial@...r.kernel.org,
	gregkh@...e.de, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org
Subject: Re: [RFC PATCH 1/2] serial: 8250: Add a notifier chain for driver
 registration.

On 03/17/2011 12:31 PM, Grant Likely wrote:
> On Thu, Mar 17, 2011 at 07:24:41PM +0000, Alan Cox wrote:
>>>> If we did that, serial8250_probe() would automatically do the right thing.
>>>
>>> Take a look at the way arch/powerpc/platforms/512x/pdm360ng.c uses a
>>> notifier for amending a platform_device with additional data..
>>
>> I tend to view arch specific embedded code as rather like very dubious
>> parties. What goes on in other peoples' house out of sight is none of my
>> business.
>>
>> The 8250 however is core code so it should keep its clothers on and behave
>> in a manner befitting its status.
>>
>> What part of the problem can't be solved by doing it properly using the
>> device registration interfaces we have today ?
>
> Device registration isn't the problem.  The problem is supplying
> machine-specific callbacks from the board support code to the
> drivers.  When devices are sourced from a device tree, it is easy to
> get data about the device out of the tree, but it is really hard to
> get callback pointers.  To make it all work without this fiddling
> about, the octeon serial_{in,out} implementation would need to be
> rolled into of_serial.c (which FWIW, I have absolutely no problem
> with).
>

The only problem I have with that is that it ends up moving chip 
specific erratum workarounds into drivers/tty/serial instead of 
arch/mips/cavium-octeon.

I will think about this more.

David Daney
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