Re: Writing a console/tty driver -- how to use tty_port?
From: Timur Tabi
Date: Thu Oct 28 2010 - 16:34:52 EST
Alan Cox wrote:
> 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 see something weird in sdio_uart_install():
int ret = tty_init_termios(tty);
if (ret == 0) {
tty_driver_kref_get(driver);
tty->count++;
/* This is the ref sdio_uart_port get provided */
tty->driver_data = port;
driver->ttys[idx] = tty;
This function is called by tty_driver_install_tty(), which also does this:
if (tty_init_termios(tty) == 0) {
lock_kernel();
tty_driver_kref_get(driver);
tty->count++;
driver->ttys[idx] = tty;
unlock_kernel();
return 0;
}
Assuming that both calls to tty_init_termios(tty) return 0, these three lines
will be executed twice:
tty_driver_kref_get(driver);
tty->count++;
driver->ttys[idx] = tty;
Is that right?
--
Timur Tabi
Linux kernel developer at Freescale
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