linux-kernel - Re: [PATCH] RFC: serial: core: Dynamic minor support

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Message-ID: <1492692258.27393.8.camel@collabora.co.uk>
Date:   Thu, 20 Apr 2017 14:44:18 +0200
From:   Sjoerd Simons <sjoerd.simons@...labora.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-serial@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org, Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH] RFC: serial: core: Dynamic minor support

On Thu, 2017-04-20 at 14:15 +0200, Greg Kroah-Hartman wrote:
> On Thu, Apr 20, 2017 at 02:03:57PM +0200, Sjoerd Simons wrote:
> > --- a/include/linux/serial_core.h
> > +++ b/include/linux/serial_core.h
> > @@ -31,6 +31,8 @@
> >  #include <linux/sysrq.h>
> >  #include <uapi/linux/serial_core.h>
> >  
> > +#define LOW_DENSITY_UART_MAJOR 204
> 
> Where are you stealing this from?

Heh, 204 is defined as the "Low-density serial ports" in
devices.txt. As documented in the commit message, i've repurposed that
for dynamic minors (if configured). Maybe it's better to request a new
major for this purpose? But then again, then just means 204 will go
unused when the option is on so...

Lots of drivers do have it as a hard-coded number, seemed sane to put
it a bit more central for some potential later cleanup in other
drivers.

> 
> > +
> >  #ifdef CONFIG_SERIAL_CORE_CONSOLE
> >  #define uart_console(port) \
> >  	((port)->cons && (port)->cons->index == (port)->line)
> > @@ -313,6 +315,10 @@ struct uart_driver {
> >  	 */
> >  	struct uart_state	*state;
> >  	struct tty_driver	*tty_driver;
> > +
> > +#ifdef CONFIG_SERIAL_DYNAMIC_MINORS
> > +	struct list_head	dynamic_uarts;
> > +#endif
> 
> Why not just always have this?

Trying to save a few bytes if the option is unused; Maybe overdoing it
:)

> Nice first try though!

Thanks, If there are no big comments onthe general approach i'll respin
without RFC soonish addressing your other comments.
-- 
Sjoerd Simons
Collabora Ltd.