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

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Date:	Mon, 28 May 2007 19:05:13 +0200
From:	Tilman Schmidt <tilman@...p.cc>
To:	"Lars K.W. Gohlke" <lkwg82@....de>
CC:	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	linux-kernel@...r.kernel.org
Subject: Re: How to access correctly serial port inside module?

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.

-- 
Tilman Schmidt                          E-Mail: tilman@...p.cc
Bonn, Germany
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