linux-kernel - Re: [PATCH 2/2] usb_serial: only allow sysrq on a console port

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Date:	Mon, 6 Jul 2009 00:38:18 -0400
From:	Robin Getz <rgetz@...ckfin.uclinux.org>
To:	"Alan Cox" <alan@...rguk.ukuu.org.uk>
CC:	greg@...ah.com, "Jason Wessel" <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 2/2] usb_serial: only allow sysrq on a console port

On Sun 5 Jul 2009 14:17, Alan Cox pondered:
> > If Jason's patch is necessary () - should this be fixed up for
> > standard UARTs too?
> 
> I think so yes, although I'd not realised it wasn't protected currently
> ?

Hmm - try as I may - I can't get this to fail - so it must be protected 
somewhere....

Ahh---

It is in include/linux/serial_core.h:uart_handle_break() - never checked the 
header for the magic before I bugged you... sorry about that...

> > The above patch would sync the (seemlying duplicated) code between
> > drivers/usb/serial/generic.c and include/linux/serial_core.h
> 
> There is a lot of near duplicate code like this. That is one reason for
> adding struct tty_port. In theory both could be collapsed into
> 
> 	int tty_port_handle_sysrq(struct tty_port *port, unsigned int ch)
> 	{
> 	}
> 
> at this point as both USB and serial layer UARTs now have a port object.
> That would just need port->sysrq collapsing into the tty_port.
> port->console sort of already is.

It appears that the usb serial doesn't handle breaks like serial_core does. (I 
don't see any support for SAK in usb_serial either?)

Maybe _that_ is the real problem that Jason is trying to work around???


> > drivers/usb/serial/generic.c
> > int usb_serial_handle_sysrq_char(struct usb_serial_port *port,
> unsigned int ch)
> > {
> >         if (port->sysrq && port->console) {
> >                 if (ch && time_before(jiffies, port->sysrq)) {
> >                         handle_sysrq(ch,
> tty_port_tty_get(&port->port));
> >                         port->sysrq = 0;
> >                         return 1;
> 
> That also looks wrong - tty_port_tty_get takes a tty kref. I will check
> that Monday and look at collapsing these int one as you note.

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