| Message ID | 20230719051613.46569-1-tony@atomide.com |
|---|---|
| State | New |
| Headers | show |
| Series | serial: core: Add sysfs links for serial core port instances for ttys | expand |
On Thu, Jul 20, 2023 at 07:13:19AM +0300, Tony Lindgren wrote: > * Andy Shevchenko <andriy.shevchenko@intel.com> [230719 13:59]: > > On Wed, Jul 19, 2023 at 08:43:21AM +0300, Tony Lindgren wrote: > > > * Andy Shevchenko <andriy.shevchenko@intel.com> [230719 05:34]: > > > > On Wed, Jul 19, 2023 at 08:16:11AM +0300, Tony Lindgren wrote: ... > > > > > And with this, we can add /dev/serial/by-id symlinks to the serial port > > > > > device instances so we can start using serial core port addressing in > > > > > addition to the legacy ttyS naming. > > > > > > > > > > The naming we can use is dev_name:0.0 where 0.0 are the serial core > > > > > controller id and port id, so for the ttyS0 example above the naming > > > > > would be 00:04.0:0.0. > > > > > > > > This is interesting idea. But any hint why it can be useful? > > > > > > If you have lots of serial ports and we are stuck with adding aliases > > > for the ports in the dts files where the ttyS naming and ordering does > > > not really help or may not necessarily make sense if the ports are on > > > different buses or domains. With CONFIG_SERIAL_8250_RUNTIME_UARTS=4, > > > the ttyS naming is only needed for the legacy ports really. > > > > I see. Does it fix the long standing issue with ttyS enumeration (on x86 > > at least) when depending on the presence of the legacy ports the HSUART > > (high speed) can preempt the legacy placeholders (ttyS0..ttyS3)? > > > > To me sounds like it may very well do fix it and I would be glad to see that > > in the commit message (as selling point) and in documentation. > > It won't affect how ttyS0..ttyS3 get assigned, but it helps finding your > HSUART instance with DEVNAME:0.0 style addressing. So you don't need to > care what ttyS number the port has. If you have such a test case maybe give > it a try. Exactly, the problem (currently) is, that depending on the BIOS settings the kernel can't use the same command line and this is quite a PITA for our customers! As far as we can specify hardware (path) to the console, it will be so cool and hopefully solves this very long standing issue.
* Andy Shevchenko <andriy.shevchenko@intel.com> [230721 10:06]: > On Thu, Jul 20, 2023 at 07:13:19AM +0300, Tony Lindgren wrote: > > * Andy Shevchenko <andriy.shevchenko@intel.com> [230719 13:59]: > > > On Wed, Jul 19, 2023 at 08:43:21AM +0300, Tony Lindgren wrote: > > > > * Andy Shevchenko <andriy.shevchenko@intel.com> [230719 05:34]: > > > > > On Wed, Jul 19, 2023 at 08:16:11AM +0300, Tony Lindgren wrote: > > ... > > > > > > > And with this, we can add /dev/serial/by-id symlinks to the serial port > > > > > > device instances so we can start using serial core port addressing in > > > > > > addition to the legacy ttyS naming. > > > > > > > > > > > > The naming we can use is dev_name:0.0 where 0.0 are the serial core > > > > > > controller id and port id, so for the ttyS0 example above the naming > > > > > > would be 00:04.0:0.0. > > > > > > > > > > This is interesting idea. But any hint why it can be useful? > > > > > > > > If you have lots of serial ports and we are stuck with adding aliases > > > > for the ports in the dts files where the ttyS naming and ordering does > > > > not really help or may not necessarily make sense if the ports are on > > > > different buses or domains. With CONFIG_SERIAL_8250_RUNTIME_UARTS=4, > > > > the ttyS naming is only needed for the legacy ports really. > > > > > > I see. Does it fix the long standing issue with ttyS enumeration (on x86 > > > at least) when depending on the presence of the legacy ports the HSUART > > > (high speed) can preempt the legacy placeholders (ttyS0..ttyS3)? > > > > > > To me sounds like it may very well do fix it and I would be glad to see that > > > in the commit message (as selling point) and in documentation. > > > > It won't affect how ttyS0..ttyS3 get assigned, but it helps finding your > > HSUART instance with DEVNAME:0.0 style addressing. So you don't need to > > care what ttyS number the port has. If you have such a test case maybe give > > it a try. > > Exactly, the problem (currently) is, that depending on the BIOS settings > the kernel can't use the same command line and this is quite a PITA for > our customers! > > As far as we can specify hardware (path) to the console, it will be so > cool and hopefully solves this very long standing issue. OK great, I'll update the patch description for next revision. Regards, Tony
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -3371,6 +3371,8 @@ static int serial_core_add_preferred_console(struct uart_driver *drv, int serial_core_register_port(struct uart_driver *drv, struct uart_port *port) { struct serial_ctrl_device *ctrl_dev, *new_ctrl_dev = NULL; + struct uart_match match = {port, drv}; + struct device *tty_dev; int ret; mutex_lock(&port_mutex); @@ -3411,10 +3413,21 @@ int serial_core_register_port(struct uart_driver *drv, struct uart_port *port) port->flags &= ~UPF_DEAD; + tty_dev = device_find_child(port->dev, &match, serial_match_port); + if (tty_dev) { + ret = sysfs_create_link(&port->port_dev->dev.kobj, &tty_dev->kobj, + "tty"); + if (ret) + goto err_remove_port; + } + mutex_unlock(&port_mutex); return 0; +err_remove_port: + serial_core_remove_one_port(drv, port); + err_unregister_port_dev: serial_base_port_device_remove(port->port_dev); @@ -3436,12 +3449,18 @@ void serial_core_unregister_port(struct uart_driver *drv, struct uart_port *port struct device *phys_dev = port->dev; struct serial_port_device *port_dev = port->port_dev; struct serial_ctrl_device *ctrl_dev = serial_core_get_ctrl_dev(port_dev); + struct uart_match match = {port, drv}; int ctrl_id = port->ctrl_id; + struct device *tty_dev; mutex_lock(&port_mutex); port->flags |= UPF_DEAD; + tty_dev = device_find_child(port->dev, &match, serial_match_port); + if (tty_dev) + sysfs_remove_link(&port->port_dev->dev.kobj, "tty"); + serial_core_remove_one_port(drv, port); /* Note that struct uart_port *port is no longer valid at this point */
Let's allow the userspace to find out the tty name for a serial core controller id if a tty exists. This can be done with: $ grep DEVNAME /sys/bus/serial-base/devices/port*/tty/uevent /sys/bus/serial-base/devices/port.00:04.0/tty/uevent:DEVNAME=ttyS0 /sys/bus/serial-base/devices/port.serial8250.1/tty/uevent:DEVNAME=ttyS1 /sys/bus/serial-base/devices/port.serial8250.2/tty/uevent:DEVNAME=ttyS2 /sys/bus/serial-base/devices/port.serial8250.3/tty/uevent:DEVNAME=ttyS3 And with this, we can add /dev/serial/by-id symlinks to the serial port device instances so we can start using serial core port addressing in addition to the legacy ttyS naming. The naming we can use is dev_name:0.0 where 0.0 are the serial core controller id and port id, so for the ttyS0 example above the naming would be 00:04.0:0.0. Signed-off-by: Tony Lindgren <tony@atomide.com> --- Note that this depends on fix for serial core port ids patch "[PATCH] serial: core: Fix serial core port id to not use port->line" --- drivers/tty/serial/serial_core.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)