linux-kernel - Re: patch "U6715 8250 serial like driver" added to gregkh-2.6 tree

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Date:	Tue, 27 Jul 2010 16:46:10 +0200
From:	Philippe Langlais <philippe.langlais@...ricsson.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ludovic BARRE <ludovic.barre@...ricsson.com>,
	Vincent GUITTOT <vincent.guittot@...ricsson.com>
Subject: Re: patch "U6715 8250 serial like driver" added to gregkh-2.6 tree



On 07/27/10 10:14, Alan Cox wrote:
>>> I think what you need to keep this clean is to create a
>>> port->set_termios() for the 8250 port (akin to
>>> port->serial_in/serial_out) which does the specials you need each end and
>>> calls the standard serial8250_set_termios)
>>>
>>>        
>> I don't think so, call a function which compute clock each time
>> we access UART registers isn't optimal, another function to overload ?
>>      
> set_termios() gets called once at init time and once each time a
> caller requests a change in serial parameters. That's not usually
> considered a hot path. I'm not suggesting you hide it in the register
> methods but add ->set_termios as a method that can be overridden, plus
> export the existing one so you can wrap it.
>
> If you can't detect the chip then create yourself a u6715 driver file
> which registers the ports you have and specifies the relevant
> serial_in/out methods and other detail as well as containing the board
> specific routines needed.
>
> See arch/arm/mach-omap2/serial.c for a ARM example doing this, where all
> the chip knowledge is nicely buried away in the platform support.
>    
We have such a platform driver, but I can't see anywhere an example of 
set_termios()
or another uart_ops function overriding.
These platform drivers only add new functions around power & clock.
Platform drivers are initialized before 8250 driver, how to override 
8250 driver ?



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