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Date: Tue, 05 Jun 2007 23:41:50 +0200
From: Tilman Schmidt <tilman@imap.cc>
Organization: me - organized??
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To: "Lars K.W. Gohlke" <lkwg82@gmx.de>
CC: huang ying <huang.ying.caritas@gmail.com>,
       Jan Engelhardt <jengelh@linux01.gwdg.de>, linux-kernel@vger.kernel.org
Subject: Re: How to access correctly serial port inside module?
References: <46485D84.1010902@gmx.de> <46489EF1.2020509@gmx.de>	 <Pine.LNX.4.61.0705142158340.9570@yvahk01.tjqt.qr>	 <4648E9F7.5090908@imap.cc> <851fc09e0705162315w3380ddabh9b9f0b2198cb8457@mail.gmail.com> <465366CB.7090608@imap.cc> <46632489.9070107@gmx.de>
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Am 03.06.2007 22:28 schrieb Lars K.W. Gohlke:
> Tilman Schmidt schrieb:
>> Am 17.05.2007 08:15 schrieb huang ying:
>>> I think the "serio" (through drivers/input/serio/serport.c) may be a
>>> choice too, like that in linux/drivers/input/mouse/sermouse.c, which
>>> is an example to program serial port in kernel space.
>> Interesting. I wonder if that would have been a better choice for
>> the Gigaset M101 driver. It seems even to have a probe mechanism
>> so one could try to determine if the expected device is really
>> connected to the port.
>=20
>> Is there any documentation on this interface? I find the source a
>> bit hard to understand, sparsely commented as it is.
>=20
> how can I open ttyS1 with major=3D4 and minor=3D65?

a) With "my" approach, ie. writing a line discipline, you open
/dev/ttyS1 in a user space program and then push your line discipline
onto it using ioctl(,TIOCSETD,).

b) With the "serio" approach, if the probe mechanism is really what
I think it is, you register your probe function and wait for it to
be called for each active serial port, then do your thing to determine
whether this is a/the port you want to use.

> Does anybody have some code to read from it the first e.g. 2bytes?

That's not how things work in the kernel. You don't "read the first
<n> bytes" at will. You have to provide means to process whatever
data happens to arrive on the serial port, as it arrives.

a) With a line discipline, you provide a callback function
".receive_buf" which will be called by the serial driver if some
data has been received, and has to process that data then and there.
You might just stow it away in a buffer of course, provided you
are sure to get around to processing it later.

b) With the "serio" interface, it seems the ".interrupt" function
serves the same purpose - though, as I said, I am not really
competent on that topic.

HTH
T.

--=20
Tilman Schmidt                          E-Mail: tilman@imap.cc
Bonn, Germany
Diese Nachricht besteht zu 100% aus wiederverwerteten Bits.
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