On Wed, Feb 19, 2020 at 02:21:13PM +0100, Johan Hovold wrote:
> 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.
Which is good, right? If I remember my tests correctly this even works
if the tty isn't opened but just "exists".
> > 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.
Yeah, wrong (and incomplete) copy of the tty_kopen_exclusive docstring.
> > + *
> > + * 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.
Ack, will send a v7 with the doc string fixed.
Thanks for taking the time to look over
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
