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    SubjectRe: Writing a console/tty driver -- how to use tty_port?
    On Wed, 27 Oct 2010 16:04:13 -0500
    Timur Tabi <timur@freescale.com> wrote:

    > Greg,
    >
    > Do you have an updated version of Tiny TTY that uses tty_port structures? I'm
    > trying to write a new TTY driver for a device that is not a UART, and I'm having
    > a hard time finding a good example. I suspect I need to understand the tty_port
    > structure, but I can't find any documentation for it.
    >
    > One specific problem I'm having is that I can't figure out how to get a
    > tty_struct pointer in my interrupt handler. The ISR gets called whenever there
    > is new input, and it needs to call tty_insert_flip_string(). But it appears
    > that it's possible to have my driver opened multiple times, each time creating a
    > new TTY. But since I can only have one interrupt handler, I don't know how to
    > determine which of the tty_structs to use. I figure tty_port is a way to
    > resolve this problem, but I don't know how to use it exactly.

    You only have one tty struct for the multiple opens.

    Basically

    tty_port - lifetime of hardware being loaded
    tty_struct - lifetime open/close (and a bit
    beyond for refs)


    So you can use tty_port_tty_get() which also knows about all the ghastly
    internal locking rules.

    Eventually the rx buffer should be moved to the tty_port which will make
    the world vastly saner.

    drivers/mmc/card/sdio_uart.c

    is in some ways the best example, it handles all the horrible cases
    including unloading of hardware v open races, its way more than you'd
    need but does illustrate it all.

    I've also got a draft tty_kfifo layer which is designed to be tty_port
    with kfifo queues as a helper. Remind me next week if it would be useful
    and I'll dig it back out.

    Alan


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