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 19:08:47 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Cc:     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()

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;

> @@ -1905,7 +1890,7 @@ struct tty_struct *tty_kopen(dev_t device)
>  


-- 
Best regards,
Jacek Anaszewski