Messages in this thread |  | | | Date | Wed, 27 Oct 2010 23:19:48 +0100 | | From | Alan Cox <> | | Subject | Re: Writing a console/tty driver -- how to use tty_port? |
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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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