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Tilman Schmidt schrieb:
Am 15.05.2007 10:43 schrieb Jan Engelhardt:
On May 15 2007 01:00, Tilman Schmidt wrote:
Am 14.05.2007 22:00 schrieb Jan Engelhardt:
On May 14 2007 19:40, Lars K.W. Gohlke wrote:
after searching the mailing list and searching the web, I still don't
know how to access correctly the serial port (in user space known as
/dev/ttyS01)
http://kernelnewbies.org/FAQ/WhyWritingFilesFromKernelIsBad
That's not nice, sending a newbie on a wild goose chase like that.
He doesn't want to write to a file from kernel after all. Reading
FAQs is never bad, of course, but reading that particular one
won't help him at all with this questions.
The original poster is quite unclear about how he wants to access the
serial port. [...]
Unfortunately, my magic sphere is out of order, so I could only take
a really really vague guess at what was wanted.
He asked about "the correct way". The document you cited will just
warn him against one of the many incorrect ones. That's less helpful
than not answering at all.
inb/inw/inl, printk, outb/outw/outl.
This is even less nice. You're sending him down the road of
directly programming UART registers, knowing full well (I hope)
that this a Bad Thing.
This is how 8250.c works.
Exactly. Which is one reason why other parts of the kernel should not
do it themselves. (Another being of course that if you do it that way,
your code will only work with that particular type of serial port
hardware. As the last of the Ten Commandments for C Programmers has
been declaring for ages, you shouldn't assume that "All the world's a
VAX^WPC.")
HTH
T.
ok, I have read everything and also have read the chapters about
tty_drivers. However I'm not really understand, how to ... .
I will summarize the concrete scenario, which will lead to the
understanding and further solution of deadling with serial driver.
[scenario]
1. in userspace I'm doing: > date > /dev/ttyS0
2. in kernelspace I want to print out this date.
[/scenario]
I'm really new to kernel coding, that's why I maybe understand some
functions not the proper way.
I'm a bit confused.
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