linux-kernel - Re: [PATCH 5/9] mfd: Add UART support for the ST-Ericsson CG2900.

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Message-ID: <AANLkTinh3D8V8UaN8FyCouwUQ98A4RRWEHXU7Tr9XMbs@mail.gmail.com>
Date:	Fri, 29 Oct 2010 13:58:51 +0200
From:	Par-Gunnar Hjalmdahl <pghatwork@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, linus.walleij@...ricsson.com,
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lukasz.Rymanowski@...to.com
Subject: Re: [PATCH 5/9] mfd: Add UART support for the ST-Ericsson CG2900.

2010/10/28 Arnd Bergmann <arnd@...db.de>:
> On Friday 22 October 2010, Par-Gunnar Hjalmdahl wrote:
>
>> >
>> > So - NAK this for the moment, it needs to be split cleanly into ldisc
>> > (thing which speaks the protocol and eg sees "speed change required" and
>> > acts on it) and device (thing which knows about the hardware).
>>
>> OK. We will try to figure out a new design.
>> I'm not too happy about putting the ldisc part in Bluetooth though
>> since it is only partly Bluetooth, it is also GPS and FM. Better could
>> maybe be under char/?
>
> After getting a better idea of what the base mfd driver does, my impression
> is now that you should not register a second N_HCI line discipline at all,
> but instead extend the existing line discipline with this number.
>
> I'm not sure what happens if you need two modules that try to register
> the same ldisc number, but I imagine it is not good.
>
> Shouldn't you instead be using the drivers/bluetooth/hci_{ldisc,h4} code?
>
>        Arnd
>

We also need the ldisc code to handle events from FM and GPS and since
that is chip specific we cannot add that to the generic hci_ldisc
code.
I agree that we might run into problems if two drivers try to register
the same line discipline. It might then be better to introduce a new
line discipline then even though that could cause other problems. I do
not know if it is possible to add a condition in Kconfig otherwise so
the CG2900 ldisc cannot be active while the "normal" ldisc driver is
selected.

/P-G
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