On Thu, Feb 13, 2020 at 10:15:58AM +0100, Uwe Kleine-König wrote:
> From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxx>
> ---
> -/**
> - * 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;
> @@ -1905,7 +1890,7 @@ struct tty_struct *tty_kopen(dev_t device)
>
> /* check whether we're reopening an existing tty */
> tty = tty_driver_lookup_tty(driver, NULL, index);
> - if (IS_ERR(tty))
> + if (IS_ERR(tty) || shared)
So here you skip initialisation and return NULL if the tty isn't already
in use (e.g. is open) when shared is set.
> goto out;
>
> if (tty) {
> @@ -1923,7 +1908,44 @@ struct tty_struct *tty_kopen(dev_t device)
> tty_driver_kref_put(driver);
> return tty;
> }
> -EXPORT_SYMBOL_GPL(tty_kopen);
> +
> +/**
> + * tty_kopen_exclusive - 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_exclusive(dev_t device)
> +{
> + return tty_kopen(device, 0);
> +}
> +EXPORT_SYMBOL_GPL(tty_kopen_exclusive);
> +
> +/**
> + * tty_kopen_shared - open a tty device for shared in-kernel use
> + * @device: dev_t of device to open
> + *
> + * Opens an already existing tty
> + * rnel. Performs the driver lookup,
"rnel"?
> + * makes sure it's not already opened and performs the first-time
> + * tty initialization.
Yet, you claim to do initialisation here, which isn't the case.
> + *
> + * Locking is identical to tty_kopen() above.
> + */
> +struct tty_struct *tty_kopen_shared(dev_t device)
> +{
> + return tty_kopen(device, 1);
> +}
> +EXPORT_SYMBOL_GPL(tty_kopen_shared);
This "kopen" naming is unfortunate as the tty isn't really opened by
either of these functions, but that's not something you introduced.
Johan
