* Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> [230131 10:10]: > On Mon, Jan 16, 2023 at 09:59:58AM +0200, Tony Lindgren wrote: > > We want to enable runtime PM for serial port device drivers in a generic > > way. To do this, we want to have the serial core layer manage the > > registered physical serial controller devices. > > > > To do this, let's set up a struct device for the serial core controller > > as suggested by Greg and Jiri. The serial core controller devices are > > children of the physical serial port device. The serial core controller > > device is needed to support multiple different kind of ports connected > > to single physical serial port device. > > > > Let's also set up a struct device for the serial core port. The serial > > core port instances are children of the serial core controller device. > > Looking better, but why is this new device a platform device? That > feels odd, you should never have a platform device hanging off of a > non-platform device, right? No special need for it to be a platform device. It just is easy to set up, and for my test case the serial port physical device is also a platform device. What's your preference here? > What does the sysfs tree look like now with this patch applied? Below are two examples of what's in sysfs. Regards, Tony 8< ----------------- On arm64 with two physical 8250 devices I have: # ls -l /sys/devices/platform/serial8250/ total 0 lrwxrwxrwx 1 root root 0 Jan 1 1970 driver -> ../../../bus/platform/drivers/serial8250 -rw-r--r-- 1 root root 4096 Jan 1 1970 driver_override -r--r--r-- 1 root root 4096 Jan 1 1970 modalias drwxr-xr-x 2 root root 0 Jan 1 1970 power drwxr-xr-x 5 root root 0 Jan 1 1970 serial-ctrl.0.auto lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../bus/platform drwxr-xr-x 4 root root 0 Jan 1 1970 tty -rw-r--r-- 1 root root 4096 Jan 1 1970 uevent # ls -l /sys/devices/platform/serial8250/serial-ctrl* total 0 lrwxrwxrwx 1 root root 0 Jan 1 1970 driver -> ../../../../bus/platform/drivers/serial-ctrl -rw-r--r-- 1 root root 4096 Jan 1 1970 driver_override -r--r--r-- 1 root root 4096 Jan 1 1970 modalias drwxr-xr-x 2 root root 0 Jan 1 1970 power drwxr-xr-x 3 root root 0 Jan 1 1970 serial-port.1.auto drwxr-xr-x 3 root root 0 Jan 1 1970 serial-port.4.auto lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem -> ../../../../bus/platform -rw-r--r-- 1 root root 4096 Jan 1 1970 uevent On x86_64 qemu with one port I have: # ls -l /sys/devices/pnp0/00:04/ total 0 lrwxrwxrwx 1 root root 0 Feb 1 06:13 driver -> ../../../bus/pnp/drivers/serial lrwxrwxrwx 1 root root 0 Feb 1 06:13 firmware_node -> ../../LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:01/PNP0501:00 -r--r--r-- 1 root root 4096 Feb 1 06:13 id -r--r--r-- 1 root root 4096 Feb 1 06:13 options -rw-r--r-- 1 root root 4096 Feb 1 06:13 resources drwxr-xr-x 3 root root 0 Feb 1 06:12 serial-ctrl.0.auto lrwxrwxrwx 1 root root 0 Feb 1 06:13 subsystem -> ../../../bus/pnp drwxr-xr-x 3 root root 0 Feb 1 06:12 tty -rw-r--r-- 1 root root 4096 Feb 1 06:12 uevent # ls -l /sys/devices/pnp0/00:04/serial-ctrl.0.auto/ total 0 lrwxrwxrwx 1 root root 0 Feb 1 06:13 driver -> ../../../../bus/platform/drivers/serial-ctrl -rw-r--r-- 1 root root 4096 Feb 1 06:13 driver_override -r--r--r-- 1 root root 4096 Feb 1 06:13 modalias drwxr-xr-x 2 root root 0 Feb 1 06:12 serial-port.1.auto lrwxrwxrwx 1 root root 0 Feb 1 06:13 subsystem -> ../../../../bus/platform -rw-r--r-- 1 root root 4096 Feb 1 06:12 uevent
