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SubjectRe: [PATCH] tty: Add EXTPROC support for LINEMODE
Howard Chu wrote:
> Alan Cox wrote:
>>>>> For Alpha this value should match OSF if possible.
>>>
>>> OSF didn't define this flag, nor did it assign that particular bit to any
>>> purpose. Is that good enough?
>>
>> Fine
>>
>>>> Are you suggesting that this is completely unfixable/unworkable? Would it be
>>>> sufficient to use kernel_termios_to_user_termios() ?
>>
>> I don't see a way to fix it sanely
>>
>>>>
>>> Actually using kernel_termios_to_user_termios_1(). In all supported
>>> architectures this structure is basically aligned with but smaller than the
>>> userland struct termios.
>>
>> The relationship isn't quite so simple and it may change in the future,
>> so this seems to be a very bad idea. Besides which syscalls are *cheap*
>> so simply notifying someone to reread the terminal data they care about
>> should be fine. In that sense it seems SVR4 got it right.

> OK. I'm fine with only setting a bit in the packet header, and letting the
> application do an ioctl/tcgetattr to discover the actual state.

Just deleting that part of the patch was simple enough. The TIOCPKT_IOCTL bit
still gets set in the packet header byte; userspace apps will just have to do
an ioctl to retrieve the state when the bit is set.

I've also added locking to the pty_signal() function. The check for tty->link
seems a bit paranoid, but a few other functions do it as well.

/* Send a signal to the slave */
static int pty_signal(struct tty_struct *tty, int sig)
{
unsigned long flags;
struct pid *pgrp;

if (tty->link) {
spin_lock_irqsave(&tty->link->ctrl_lock, flags);
pgrp = get_pid(tty->link->pgrp);
spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);

kill_pgrp(pgrp, sig, 1);
put_pid(pgrp);
}
return 0;
}

That covers all the feedback so far. I'll be reposting the entire patch again
shortly, unless you have any additional thoughts.

--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/


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