2019-01-28 06:54:49

by Myungho Jung

[permalink] [raw]
Subject: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()

tty_set_termios() should be called with slave side of pty driver. So, If
tty driver is pty master, it needs to be switched to ->link.

Reported-by: [email protected]
Signed-off-by: Myungho Jung <[email protected]>
---
drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index fbf7b4df23ab..90c5ea8c399b 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
return 0;
}

+/* If driver is pty master, return slave side */
+static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
+{
+ return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+ tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
+}
+
/* Flow control or un-flow control the device */
void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
{
struct tty_struct *tty = hu->tty;
+ struct tty_struct *real_tty;
struct ktermios ktermios;
int status;
unsigned int set = 0;
@@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
return;
}

+ real_tty = hci_uart_get_real_tty(tty);
if (enable) {
/* Disable hardware flow control */
- ktermios = tty->termios;
+ ktermios = real_tty->termios;
ktermios.c_cflag &= ~CRTSCTS;
- status = tty_set_termios(tty, &ktermios);
+ status = tty_set_termios(real_tty, &ktermios);
BT_DBG("Disabling hardware flow control: %s",
status ? "failed" : "success");

@@ -350,9 +359,9 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
BT_DBG("Setting RTS: %s", status ? "failed" : "success");

/* Re-enable hardware flow control */
- ktermios = tty->termios;
+ ktermios = real_tty->termios;
ktermios.c_cflag |= CRTSCTS;
- status = tty_set_termios(tty, &ktermios);
+ status = tty_set_termios(real_tty, &ktermios);
BT_DBG("Enabling hardware flow control: %s",
status ? "failed" : "success");
}
@@ -367,9 +376,10 @@ void hci_uart_set_speeds(struct hci_uart *hu, unsigned int init_speed,

void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed)
{
- struct tty_struct *tty = hu->tty;
+ struct tty_struct *tty;
struct ktermios ktermios;

+ tty = hci_uart_get_real_tty(hu->tty);
ktermios = tty->termios;
ktermios.c_cflag &= ~CBAUD;
tty_termios_encode_baud_rate(&ktermios, speed, speed);
--
2.17.1



2019-01-28 12:20:52

by Marcel Holtmann

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()

Hi Myungho,

> tty_set_termios() should be called with slave side of pty driver. So, If
> tty driver is pty master, it needs to be switched to ->link.
>
> Reported-by: [email protected]
> Signed-off-by: Myungho Jung <[email protected]>
> ---
> drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index fbf7b4df23ab..90c5ea8c399b 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> return 0;
> }
>
> +/* If driver is pty master, return slave side */
> +static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
> +{
> + return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> + tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
> +}
> +

if (tty->driver->type == TTY_DRIVER_PTY && tty->driver->subtype = PTY_TYPE_MASTER)
return tty->link;

return tty;

We can spare the extra two lines to make this readable.

> /* Flow control or un-flow control the device */
> void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> {
> struct tty_struct *tty = hu->tty;
> + struct tty_struct *real_tty;
> struct ktermios ktermios;
> int status;
> unsigned int set = 0;
> @@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> return;
> }
>
> + real_tty = hci_uart_get_real_tty(tty);

I would add a comment above this call why this is done and then also add an empty line after it. The if clause is not related to that call at all.

> if (enable) {
> /* Disable hardware flow control */
> - ktermios = tty->termios;
> + ktermios = real_tty->termios;
> ktermios.c_cflag &= ~CRTSCTS;
> - status = tty_set_termios(tty, &ktermios);
> + status = tty_set_termios(real_tty, &ktermios);
> BT_DBG("Disabling hardware flow control: %s",
> status ? "failed" : "success");
>
> @@ -350,9 +359,9 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> BT_DBG("Setting RTS: %s", status ? "failed" : "success");
>
> /* Re-enable hardware flow control */
> - ktermios = tty->termios;
> + ktermios = real_tty->termios;
> ktermios.c_cflag |= CRTSCTS;
> - status = tty_set_termios(tty, &ktermios);
> + status = tty_set_termios(real_tty, &ktermios);
> BT_DBG("Enabling hardware flow control: %s",
> status ? "failed" : "success");
> }
> @@ -367,9 +376,10 @@ void hci_uart_set_speeds(struct hci_uart *hu, unsigned int init_speed,
>
> void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed)
> {
> - struct tty_struct *tty = hu->tty;
> + struct tty_struct *tty;
> struct ktermios ktermios;
>
> + tty = hci_uart_get_real_tty(hu->tty);

Same here. Add comment above and the also an extra empty line.

> ktermios = tty->termios;
> ktermios.c_cflag &= ~CBAUD;
> tty_termios_encode_baud_rate(&ktermios, speed, speed);

Regards

Marcel


2019-01-30 10:10:09

by Johan Hovold

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()

On Sun, Jan 27, 2019 at 10:53:02PM -0800, Myungho Jung wrote:
> tty_set_termios() should be called with slave side of pty driver. So, If
> tty driver is pty master, it needs to be switched to ->link.

I'm not sure that's the right solution. PTYs are virtual devices used
for IPC and neither end (master or slave) have support for modem
control or baud rates.

> Reported-by: [email protected]
> Signed-off-by: Myungho Jung <[email protected]>
> ---
> drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index fbf7b4df23ab..90c5ea8c399b 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> return 0;
> }
>
> +/* If driver is pty master, return slave side */
> +static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
> +{
> + return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> + tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
> +}
> +
> /* Flow control or un-flow control the device */
> void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> {
> struct tty_struct *tty = hu->tty;
> + struct tty_struct *real_tty;
> struct ktermios ktermios;
> int status;
> unsigned int set = 0;
> @@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> return;
> }
>
> + real_tty = hci_uart_get_real_tty(tty);
> if (enable) {
> /* Disable hardware flow control */
> - ktermios = tty->termios;
> + ktermios = real_tty->termios;
> ktermios.c_cflag &= ~CRTSCTS;
> - status = tty_set_termios(tty, &ktermios);
> + status = tty_set_termios(real_tty, &ktermios);
> BT_DBG("Disabling hardware flow control: %s",
> status ? "failed" : "success");

So instead of these pointless calls to set the slave termios and
modem-control state, you might as well bail out early above (and
similarly in set_baudrate()).

Using n_hci for a master pty really makes no sense at all, so we could
even bail out at ldisc open, but perhaps that can be discussed and
addressed later.

Johan

2019-01-31 05:14:19

by Myungho Jung

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()

On Wed, Jan 30, 2019 at 11:07:38AM +0100, Johan Hovold wrote:
> On Sun, Jan 27, 2019 at 10:53:02PM -0800, Myungho Jung wrote:
> > tty_set_termios() should be called with slave side of pty driver. So, If
> > tty driver is pty master, it needs to be switched to ->link.
>
> I'm not sure that's the right solution. PTYs are virtual devices used
> for IPC and neither end (master or slave) have support for modem
> control or baud rates.
>
> > Reported-by: [email protected]
> > Signed-off-by: Myungho Jung <[email protected]>
> > ---
> > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> > 1 file changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> > index fbf7b4df23ab..90c5ea8c399b 100644
> > --- a/drivers/bluetooth/hci_ldisc.c
> > +++ b/drivers/bluetooth/hci_ldisc.c
> > @@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> > return 0;
> > }
> >
> > +/* If driver is pty master, return slave side */
> > +static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
> > +{
> > + return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> > + tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
> > +}
> > +
> > /* Flow control or un-flow control the device */
> > void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > {
> > struct tty_struct *tty = hu->tty;
> > + struct tty_struct *real_tty;
> > struct ktermios ktermios;
> > int status;
> > unsigned int set = 0;
> > @@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > return;
> > }
> >
> > + real_tty = hci_uart_get_real_tty(tty);
> > if (enable) {
> > /* Disable hardware flow control */
> > - ktermios = tty->termios;
> > + ktermios = real_tty->termios;
> > ktermios.c_cflag &= ~CRTSCTS;
> > - status = tty_set_termios(tty, &ktermios);
> > + status = tty_set_termios(real_tty, &ktermios);
> > BT_DBG("Disabling hardware flow control: %s",
> > status ? "failed" : "success");
>
> So instead of these pointless calls to set the slave termios and
> modem-control state, you might as well bail out early above (and
> similarly in set_baudrate()).
>
> Using n_hci for a master pty really makes no sense at all, so we could
> even bail out at ldisc open, but perhaps that can be discussed and
> addressed later.
>
> Johan

Hi Johan,

I fixed it to just return -EOPNOTSUPP if NULL in ath_setup().

Thanks,
Myungho

2019-01-31 15:44:00

by Johan Hovold

[permalink] [raw]
Subject: Re: [PATCH] Bluetooth: hci_uart: Switch pty driver to slave side in tty_set_termios()

On Wed, Jan 30, 2019 at 09:13:53PM -0800, Myungho Jung wrote:
> On Wed, Jan 30, 2019 at 11:07:38AM +0100, Johan Hovold wrote:
> > On Sun, Jan 27, 2019 at 10:53:02PM -0800, Myungho Jung wrote:
> > > tty_set_termios() should be called with slave side of pty driver. So, If
> > > tty driver is pty master, it needs to be switched to ->link.
> >
> > I'm not sure that's the right solution. PTYs are virtual devices used
> > for IPC and neither end (master or slave) have support for modem
> > control or baud rates.
> >
> > > Reported-by: [email protected]
> > > Signed-off-by: Myungho Jung <[email protected]>
> > > ---
> > > drivers/bluetooth/hci_ldisc.c | 20 +++++++++++++++-----
> > > 1 file changed, 15 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> > > index fbf7b4df23ab..90c5ea8c399b 100644
> > > --- a/drivers/bluetooth/hci_ldisc.c
> > > +++ b/drivers/bluetooth/hci_ldisc.c
> > > @@ -299,10 +299,18 @@ static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
> > > return 0;
> > > }
> > >
> > > +/* If driver is pty master, return slave side */
> > > +static struct tty_struct *hci_uart_get_real_tty(struct tty_struct *tty)
> > > +{
> > > + return (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
> > > + tty->driver->subtype == PTY_TYPE_MASTER) ? tty->link : tty;
> > > +}
> > > +
> > > /* Flow control or un-flow control the device */
> > > void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > > {
> > > struct tty_struct *tty = hu->tty;
> > > + struct tty_struct *real_tty;
> > > struct ktermios ktermios;
> > > int status;
> > > unsigned int set = 0;
> > > @@ -314,11 +322,12 @@ void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
> > > return;
> > > }
> > >
> > > + real_tty = hci_uart_get_real_tty(tty);
> > > if (enable) {
> > > /* Disable hardware flow control */
> > > - ktermios = tty->termios;
> > > + ktermios = real_tty->termios;
> > > ktermios.c_cflag &= ~CRTSCTS;
> > > - status = tty_set_termios(tty, &ktermios);
> > > + status = tty_set_termios(real_tty, &ktermios);
> > > BT_DBG("Disabling hardware flow control: %s",
> > > status ? "failed" : "success");
> >
> > So instead of these pointless calls to set the slave termios and
> > modem-control state, you might as well bail out early above (and
> > similarly in set_baudrate()).
> >
> > Using n_hci for a master pty really makes no sense at all, so we could
> > even bail out at ldisc open, but perhaps that can be discussed and
> > addressed later.

> I fixed it to just return -EOPNOTSUPP if NULL in ath_setup().

That was the other fix. For this one you need to bail out if the tty is
a pty master so that tty_set_termios never gets called here or in
set_baudrate(). Possibly you can do that already at open().

This is also being discussed here:

https://lkml.kernel.org/r/20190130103227.GR3691@localhost

Johan