linux-kernel - Re: How to access correctly serial port inside module?

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Message-ID: <465D22A6.4090107@gmx.de>
Date:	Wed, 30 May 2007 09:07:18 +0200
From:	"Lars K.W. Gohlke" <lkwg82@....de>
To:	Tilman Schmidt <tilman@...p.cc>
CC:	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	linux-kernel@...r.kernel.org
Subject: Re: How to access correctly serial port inside module?

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Tilman Schmidt schrieb:
> Am 24.05.2007 21:15 schrieb Lars K.W. Gohlke:
>> Jan Engelhardt schrieb:
> [code proposal]
>>> [I've warned about it... ;-) ]
>> is it the way to access from kernelspace the userspace fs?
>> the not-correct-way?
>
> Yes, indeed.
>
>> If it is so, I will wait for another solution ;)
>
> I'm not sure waiting will help. The roasted pigeons will not come
> flying into your mouth.
>
> The possible solutions have been sketched out for you:
>
> a) open the device file from the kernel (described by Jan):
>    actively discouraged by the kernelnewbies.org FAQ document,
>    and probably won't even work IMHO
>
> b) program the serial port directly (described by Jan):
>    will work only with one type of hardware and you'll have to
>    disable the regular serial driver first; frowned upon by kernel
>    gurus as "reinventing the wheel"
>
> c) abuse the line discipline interface (described by me):
>    moderately well documented, and there's precedent for using it
>    that way in the well-accepted PPP module as well as my humble
>    contribution, the ser_gigaset driver; requires a userspace
>    daemon for pushing the line discipline module on the serial
>    port and keeping it there
>
> d) use the serio interface (described by Ying Huang):
>    potentially cleaner conceptually and seems to work without a
>    userspace daemon, but apparently not documented anywhere
>    except in the source files drivers/input/serio/serport.c
>    and linux/drivers/input/mouse/sermouse.c
>
> Now it's your turn to decide.
>
> HTH
> T.
>

When I'm chosing option d) can smb. help me step by step? There are so
many pieces of code I don't understand.

Ok, let's begin:

my kernel source base is : ubuntu-lts 6.06 and 2.6.15-7
http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.15.y.git;a=tree;f=drivers/input/serio;

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