On Wed, 2026-09-30 at 17:32 +0000, Markus Probst wrote:
These functions will be used to simply the serdev rust abstraction. It also contributes to the fixing of 2 race conditions in the serdev rust abstraction.
Signed-off-by: Markus Probst markus.probst@posteo.de
drivers/tty/serdev/core.c | 44 ++++++++++++++++++++++++++++++++++++- drivers/tty/serdev/serdev-ttyport.c | 33 ++++++++++++++++++++++++++++ include/linux/serdev.h | 6 +++++ 3 files changed, 82 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c index 77e8e1d4d2a6..af1470e33620 100644 --- a/drivers/tty/serdev/core.c +++ b/drivers/tty/serdev/core.c @@ -191,6 +191,45 @@ void serdev_device_close(struct serdev_device *serdev) } EXPORT_SYMBOL_GPL(serdev_device_close); +/**
- serdev_device_pause_rx() - pause data receive
- @serdev: serdev device
- Pause calls to receive_buf.
- Note that if a call to receive_buf is currently executed, the function will
- sleep until it has finished.
- */
+void serdev_device_pause_rx(struct serdev_device *serdev) +{
- struct serdev_controller *ctrl = serdev->ctrl;
- if (!ctrl || !ctrl->ops->pause_rx)
return;- ctrl->ops->pause_rx(ctrl);
+} +EXPORT_SYMBOL_GPL(serdev_device_pause_rx);
+/**
- serdev_device_resume_rx() - resume data receive
- @serdev: serdev device
- Resume calls to receive_buf.
- This can be called even if not paused to ensure data receive is active.
- */
+void serdev_device_resume_rx(struct serdev_device *serdev) +{
- struct serdev_controller *ctrl = serdev->ctrl;
- if (!ctrl || !ctrl->ops->resume_rx)
return;- ctrl->ops->resume_rx(ctrl);
+} +EXPORT_SYMBOL_GPL(serdev_device_resume_rx);
static void devm_serdev_device_close(void *serdev) { serdev_device_close(serdev); @@ -402,6 +441,7 @@ EXPORT_SYMBOL_GPL(serdev_device_break_ctl); static int serdev_drv_probe(struct device *dev) { const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver);
- struct serdev_device *sdev = to_serdev_device(dev); int ret;
ret = dev_pm_domain_attach(dev, PD_FLAG_ATTACH_POWER_ON | @@ -409,7 +449,9 @@ static int serdev_drv_probe(struct device *dev) if (ret) return ret;
- return sdrv->probe(to_serdev_device(dev));
- serdev_device_resume_rx(sdev);
- return sdrv->probe(sdev);
} static void serdev_drv_remove(struct device *dev) diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c index c11908f5e1ce..2bed0e54202a 100644 --- a/drivers/tty/serdev/serdev-ttyport.c +++ b/drivers/tty/serdev/serdev-ttyport.c @@ -7,8 +7,10 @@ #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/poll.h> +#include "../tty.h" #define SERPORT_ACTIVE 1 +#define SERPORT_PAUSE_RX 2 struct serport { struct tty_port *port; @@ -35,6 +37,9 @@ static size_t ttyport_receive_buf(struct tty_port *port, const u8 *cp, if (!test_bit(SERPORT_ACTIVE, &serport->flags)) return 0;
- if (test_bit(SERPORT_PAUSE_RX, &serport->flags))
return 0;- ret = serdev_controller_receive_buf(ctrl, cp, count);
dev_WARN_ONCE(&ctrl->dev, ret > count, @@ -177,6 +182,32 @@ static bool ttyport_close(struct serdev_controller *ctrl) return true; } +static void ttyport_pause_rx(struct serdev_controller *ctrl) +{
- struct serport *serport = serdev_controller_get_drvdata(ctrl);
- struct tty_struct *tty = serport->tty;
- guard(mutex)(&serport->lock);
- set_bit(SERPORT_PAUSE_RX, &serport->flags);
- if (test_bit(SERPORT_ACTIVE, &serport->flags))
tty_buffer_flush_work(tty->port);
I just realised this could result in a deadlock.
Since the mutex already prevents calling of `serdev_controller_receive_buf`, it is safe to completely remove this section (if statement + `tty_buffer_flush_work`).
Thanks - Markus Probst
+}
+static void ttyport_resume_rx(struct serdev_controller *ctrl) +{
- struct serport *serport = serdev_controller_get_drvdata(ctrl);
- struct tty_struct *tty = serport->tty;
- guard(mutex)(&serport->lock);
- clear_bit(SERPORT_PAUSE_RX, &serport->flags);
- if (test_bit(SERPORT_ACTIVE, &serport->flags))
tty_buffer_restart_work(tty->port);+}
static unsigned int ttyport_set_baudrate(struct serdev_controller *ctrl, unsigned int speed) { struct serport *serport = serdev_controller_get_drvdata(ctrl); @@ -281,6 +312,8 @@ static const struct serdev_controller_ops ctrl_ops = { .get_tiocm = ttyport_get_tiocm, .set_tiocm = ttyport_set_tiocm, .break_ctl = ttyport_break_ctl,
- .pause_rx = ttyport_pause_rx,
- .resume_rx = ttyport_resume_rx,
}; struct device *serdev_tty_port_register(struct tty_port *port, diff --git a/include/linux/serdev.h b/include/linux/serdev.h index 0f4e81c0950d..02773554e759 100644 --- a/include/linux/serdev.h +++ b/include/linux/serdev.h @@ -89,6 +89,8 @@ struct serdev_controller_ops { int (*get_tiocm)(struct serdev_controller *); int (*set_tiocm)(struct serdev_controller *, unsigned int, unsigned int); int (*break_ctl)(struct serdev_controller *ctrl, unsigned int break_state);
- void (*pause_rx)(struct serdev_controller *ctrl);
- void (*resume_rx)(struct serdev_controller *ctrl);
}; /** @@ -194,6 +196,8 @@ static inline size_t serdev_controller_receive_buf(struct serdev_controller *ctr int serdev_device_open(struct serdev_device *); void serdev_device_close(struct serdev_device *); int devm_serdev_device_open(struct device *, struct serdev_device *); +void serdev_device_pause_rx(struct serdev_device *serdev); +void serdev_device_resume_rx(struct serdev_device *serdev); unsigned int serdev_device_set_baudrate(struct serdev_device *, unsigned int); void serdev_device_set_flow_control(struct serdev_device *, bool); int serdev_device_write_buf(struct serdev_device *, const u8 *, size_t); @@ -233,6 +237,8 @@ static inline int serdev_device_open(struct serdev_device *sdev) return -ENODEV; } static inline void serdev_device_close(struct serdev_device *sdev) {} +static inline void serdev_device_pause_rx(struct serdev_device *serdev) {} +static inline void serdev_device_resume_rx(struct serdev_device *serdev) {} static inline unsigned int serdev_device_set_baudrate(struct serdev_device *sdev, unsigned int baudrate) { return 0;