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    SubjectRe: 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.
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    fn:Lars K.W. Gohlke
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