linux-kernel - Re: [PATCH v4 1/3] tty: rename tty_kopen() and add new function tty_kopen

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Date:   Tue, 17 Dec 2019 19:20:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Pavel Machek <pavel@....cz>,
        Dan Murphy <dmurphy@...com>, Jiri Slaby <jslaby@...e.com>,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v4 1/3] tty: rename tty_kopen() and add new function
 tty_kopen_shared()

On Tue, Dec 17, 2019 at 07:08:47PM +0100, Jacek Anaszewski wrote:
> Hi Uwe,
> 
> I wanted to test the set but unfortunately this
> patch does not apply. See below for the apparent reason.
> 
> On 12/17/19 5:58 PM, Uwe Kleine-König wrote:
> > Introduce a new function tty_kopen_shared() that yields a struct
> > tty_struct. The semantic difference to tty_kopen() is that the tty is
> > expected to be used already. So rename tty_kopen() to
> > tty_kopen_exclusive() for clearness, adapt the single user and put the
> > common code in a new static helper function.
> > 
> > tty_kopen_shared is to be used to implement an LED trigger for tty
> > devices in one of the next patches.
> > 
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > ---
> >  drivers/staging/speakup/spk_ttyio.c |  2 +-
> >  drivers/tty/tty_io.c                | 58 ++++++++++++++++++++---------
> >  include/linux/tty.h                 |  5 ++-
> >  3 files changed, 44 insertions(+), 21 deletions(-)
> > 
> > diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
> > index 5a9eff08cb96..e9db06eae875 100644
> > --- a/drivers/staging/speakup/spk_ttyio.c
> > +++ b/drivers/staging/speakup/spk_ttyio.c
> > @@ -147,7 +147,7 @@ static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
> >  	if (ret)
> >  		return ret;
> >  
> > -	tty = tty_kopen(dev);
> > +	tty = tty_kopen_exclusive(dev);
> >  	if (IS_ERR(tty))
> >  		return PTR_ERR(tty);
> >  
> > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> > index a1453fe10862..b718666ce73c 100644
> > --- a/drivers/tty/tty_io.c
> > +++ b/drivers/tty/tty_io.c
> > @@ -1875,22 +1875,7 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
> >  	return driver;
> >  }
> >  
> > -/**
> > - *	tty_kopen	-	open a tty device for kernel
> > - *	@device: dev_t of device to open
> > - *
> > - *	Opens tty exclusively for kernel. Performs the driver lookup,
> > - *	makes sure it's not already opened and performs the first-time
> > - *	tty initialization.
> > - *
> > - *	Returns the locked initialized &tty_struct
> > - *
> > - *	Claims the global tty_mutex to serialize:
> > - *	  - concurrent first-time tty initialization
> > - *	  - concurrent tty driver removal w/ lookup
> > - *	  - concurrent tty removal from driver table
> > - */
> > -struct tty_struct *tty_kopen(dev_t device)
> > +static struct tty_struct *tty_kopen(dev_t device, int shared)
> >  {
> >  	struct tty_struct *tty;
> >  	struct tty_driver *driver;
> 
> In mainline, even in v5.5-rc2 we have here NULL assignment:
> 
> struct tty_driver *driver = NULL;

This is based on a patch that is already in my tty-testing tree and that
was posted earlier.  It should show up in linux-next in a day or so.

thanks,

greg k-h