Messages in this thread | | | Date | Thu, 24 May 2007 12:22:34 +0200 | From | "Lars K.W. Gohlke" <> | Subject | Re: How to access correctly serial port inside module? |
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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. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (MingW32) - GPGrelay v0.959
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