On Sun, Sep 20, 2026 at 02:29:58PM +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 | 50 ++++++++++++++++++++++++++++++++++++- drivers/tty/serdev/serdev-ttyport.c | 38 ++++++++++++++++++++++++++++ include/linux/serdev.h | 6 +++++ 3 files changed, 93 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c index 7500efcdfc21..7d24f16710cb 100644 --- a/drivers/tty/serdev/core.c +++ b/drivers/tty/serdev/core.c @@ -187,6 +187,51 @@ 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.
- The caller must guarantee that this does not run concurrently with
- `serdev_device_open` or `serdev_device_close`.
- 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.
- The caller must guarantee that this does not run concurrently with
- `serdev_device_open` or `serdev_device_close`.
- 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); @@ -398,6 +443,7 @@ 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 | @@ -405,7 +451,9 @@ 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 bab1b143b8a6..e8aa89e733bd 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; @@ -32,6 +34,14 @@ 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;- /*
* Ensure writes by the driver are visible before allowing traffic to resume.*/- smp_mb__after_atomic();
This scares me. Why not use a real lock? WHat's the issue here, you need this to be "flushed" before this call:
- ret = serdev_controller_receive_buf(ctrl, cp, count);
here?
And you just tested a bit, you didn't set a bit, so what are you trying to ensure is written exactly?
dev_WARN_ONCE(&ctrl->dev, ret > count, @@ -156,6 +166,32 @@ static void ttyport_close(struct serdev_controller *ctrl) tty_release_struct(tty, serport->tty_idx); } +static void ttyport_pause_rx(struct serdev_controller *ctrl) +{
- struct serport *serport = serdev_controller_get_drvdata(ctrl);
- struct tty_struct *tty = serport->tty;
- set_bit(SERPORT_PAUSE_RX, &serport->flags);
- if (test_bit(SERPORT_ACTIVE, &serport->flags))
What keeps this bit from being set right after you test it?
tty_buffer_flush_work(tty->port);+}
+static void ttyport_resume_rx(struct serdev_controller *ctrl) +{
- struct serport *serport = serdev_controller_get_drvdata(ctrl);
- struct tty_struct *tty = serport->tty;
- /*
* Ensure writes by the driver are visible before allowing traffic to resume.*/- smp_mb__before_atomic();
- clear_bit(SERPORT_PAUSE_RX, &serport->flags);
- if (test_bit(SERPORT_ACTIVE, &serport->flags))
Same here. Are you sure you don't need locks? This feels wrong.
thanks,
greg k-h