> -----Original Message-----
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> Sent: 2023年3月15日 19:10
> To: Sherry Sun <sherry.sun@xxxxxxx>
> Cc: jirislaby@xxxxxxxxxx; robh@xxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: Re: [PATCH] tty: serdev: serdev-ttyport: add devt for ctrl->dev
>
> On Wed, Mar 15, 2023 at 06:54:00PM +0800, Sherry Sun wrote:
> > For serdev framework, the serdev_controller device is the tty device,
> > which is also the child device of the uart_port device. If we don't
> > set devt property for ctrl->dev, device_find_child(uport->dev, ...)
> > may always return NULL in uart_suspend_port() function, which prevents
> > us from properly handling uart port suspend, so fix it here.
> >
> > Fixes: bed35c6dfa6a ("serdev: add a tty port controller driver")
> > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
> > ---
> > drivers/tty/serdev/serdev-ttyport.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/tty/serdev/serdev-ttyport.c
> > b/drivers/tty/serdev/serdev-ttyport.c
> > index bba37ab90215..c58af8141380 100644
> > --- a/drivers/tty/serdev/serdev-ttyport.c
> > +++ b/drivers/tty/serdev/serdev-ttyport.c
> > @@ -268,6 +268,7 @@ struct device *serdev_tty_port_register(struct
> > tty_port *port, {
> > struct serdev_controller *ctrl;
> > struct serport *serport;
> > + dev_t devt = MKDEV(drv->major, drv->minor_start) + idx;
> > int ret;
> >
> > if (!port || !drv || !parent)
> > @@ -282,6 +283,7 @@ struct device *serdev_tty_port_register(struct
> tty_port *port,
> > serport->tty_idx = idx;
> > serport->tty_drv = drv;
> >
> > + ctrl->dev.devt = devt;
>
> This feels wrong as you can't just create a magic dev_t out of no where and
> expect it to be handled properly. Where now is this dev_t exposed?
>
Hi Greg,
Now dev_t is the key point to get the tty->dev in uart_suspend_port()/uart_resume_port() and alloc_tty_struct(), it is set in tty_register_device_attr() but not in serdev_tty_port_register().
To be frank, I am also not sure if this is the right way to fix the issue, maybe we can have more discussion here regarding how to get the correct tty_dev in uart_suspend_port().
At least with the code logic in serdev framework we are using now, we will always get NULL tty_dev from device_find_child(). I believe this is not what we want here.
static int serial_match_port(struct device *dev, void *data)
{
struct uart_match *match = data;
struct tty_driver *tty_drv = match->driver->tty_driver;
dev_t devt = MKDEV(tty_drv->major, tty_drv->minor_start) +
match->port->line;
return dev->devt == devt; /* Actually, only one tty per port */
}
int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
{
struct uart_state *state = drv->state + uport->line;
struct tty_port *port = &state->port;
struct device *tty_dev;
struct uart_match match = {uport, drv};
mutex_lock(&port->mutex);
tty_dev = device_find_child(uport->dev, &match, serial_match_port);
if (uport->line == 2)
if (tty_dev && device_may_wakeup(tty_dev)) {
enable_irq_wake(uport->irq);
put_device(tty_dev);
mutex_unlock(&port->mutex);
return 0;
}
put_device(tty_dev);
...
Best Regards
Sherry
> Something else feels wrong here, sorry, I do not think this is correct.
>
> thanks,
>
> greg k-h
