| Message ID | 20230719051613.46569-1-tony@atomide.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | serial: core: Add sysfs links for serial core port instances for ttys | expand |
On Wed, Jul 19, 2023 at 08:16:11AM +0300, Tony Lindgren wrote: > 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 What part is the controller ID here? We also have something in procfs (I don't remember what info exactly is there). > 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?
* Andy Shevchenko <andriy.shevchenko@intel.com> [230719 05:34]: > On Wed, Jul 19, 2023 at 08:16:11AM +0300, Tony Lindgren wrote: > > 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 > > What part is the controller ID here? Oh looks like controller id it's missing in the name, I'll send a fix for that. > We also have something in procfs (I don't remember what info exactly is there). Do you mean /proc/devices? > > 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. Regards, Tony
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: > > > 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 > > > > What part is the controller ID here? > > Oh looks like controller id it's missing in the name, I'll send a fix > for that. > > > We also have something in procfs (I don't remember what info exactly is there). > > Do you mean /proc/devices? Something tty specific, /proc/tty/, but I had a look and it seems for another stuff. > > > 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.
* 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: > > > > 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 > > > > > > What part is the controller ID here? > > > > Oh looks like controller id it's missing in the name, I'll send a fix > > for that. > > > > > We also have something in procfs (I don't remember what info exactly is there). > > > > Do you mean /proc/devices? > > Something tty specific, /proc/tty/, but I had a look and it seems for another > stuff. OK > > > > 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. Regards, Tony
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(+)