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

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Date:	Sun, 5 Jul 2009 19:17:51 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Robin Getz <rgetz@...ckfin.uclinux.org>
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

> 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 ?
> 
> Make sure that only serial console (not _any_ serial port) responds to 
> sysrq (or should something else be ensuring that this isn't set when 
> the port !console? (I didn't see anything in serial_core.c?)

will check

> 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.

> Greg?
> 
> 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.

Alan
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