Re: [PATCH v2 1/1] serial: core: Fix serial_base_match() after fixing controller port name

From: Guenter Roeck
Date: Sat Aug 05 2023 - 06:50:38 EST

On 8/4/23 21:49, Tony Lindgren wrote:
* Guenter Roeck <linux@xxxxxxxxxxxx> [230804 21:42]:
On Thu, Aug 03, 2023 at 10:10:32AM +0300, Tony Lindgren wrote:
While fixing DEVNAME to be more usable, I broke serial_base_match() as the
ctrl and port prefix for device names seemed unnecessary.

The prefixes are still needed by serial_base_match() to probe the serial
base controller port, and serial tx is now broken.

Let's fix the issue by checking against dev->type and drv->name instead
of the prefixes that are no longer in the DEVNAME.

Fixes: 1ef2c2df1199 ("serial: core: Fix serial core controller port name to show controller id")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>

With this patch applied, I see the following traceback in the pending-fixes

Bisect log attached as well. It actually points to commit d962de6ae51f
("serial: core: Fix serial core port id to not use port->line").
Bisect was on mips, but I also see problems on arm, ppc, and sparc.
sparc boot tests show the warning message and then stall until aborted
(which of course may be a different problem).

Sorry about all the hassles and thanks for testing again.

I too noticed several issues remaining after testing reloading the hardware
specific serial driver, the issues I saw should be fixed in tty-linus.

kobject: kobject_add_internal failed for serial8250.0:0.0 with -EEXIST, don't try to register things with the same name in the same directory.
serial8250 serial8250.0: unable to register port at index 1 (IO2f8 MEM0 IRQ3): -17
sysfs: cannot create duplicate filename '/devices/platform/serial8250.0/serial8250.0:0/serial8250.0:0.0'

The issue above should be fixed with commit:

bbb4abb1bcfb ("serial: 8250: Reinit port_id when adding back serial8250_isa_devs")

No. I tested the tip of tty-linus (v6.5-rc4-9-gdfe2aeb226fd) which includes
above commit, but still see the problem. sparc images also still stall after
the "cannot create duplicate filename" message.
I bisected the sparc problem - it also bisects to commit d962de6ae51f.

The problem affects all mips boot tests, all sparc boot tests, as well as
arm sx1, ppc bamboo and sam460ex emulations. As far as I can see, those
call serial8250_register_8250_port() without calling serial8250_setup_port()
and thus don't set port_id. I am only testing a few of those, so I strongly
suspect that all similar callers of serial8250_register_8250_port() are
affected (i.e., almost all of them) if they register more than one serial port.