Re: patch "USB: serial: cp210x: add support for GPIOs on CP2108" added to usb-next

On Thu, Jul 01, 2021 at 04:58:09AM +0000, Tung Pham wrote:

quoted

Are you sure you're using the latest mainline kernel here, that is,
5.13 here?  With recent kernel's you would not see -ENODEV ("No such
device") but rather -EINVAL ("Invalid argument").  What does "uname
-a" say?

I use the kernel 5.8.0-59-generic, I think either result ("No such
device") or  ("Invalid argument") may be accepted in this case.

Yes, you should be able to apply this patch to older kernels without
many additional changes, but you should still mention which kernel
you're using since backporting may not always work as expected.

quoted

And which version of the patch are you applying? Are you sure it's
the latest?

I apply patch V13 from last mail that you send.

Good.

quoted

quoted

But when I test the branch of Mr Gregkh.
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/tree/dr
ivers/usb/serial/cp210x.c?h=usb-testing
root@ubuntu:/sys/class/gpio# echo 496 > /sys/class/gpio/export 
root@ubuntu:/sys/class/gpio# echo 497 > /sys/class/gpio/export That 
mean it still use GPIO 0 and GPIO 1 as GPIO functions.

quoted

It does seem that way, but to be sure, do the

quoted

      /sys/class/gpio/gpio496
     /sys/class/gpio/gpio497

quoted

directories show up as well?

Today I retest it and it seem everything is ok. May be previous test I
have some loading driver problem. The result is as below:

echo 496 > /sys/class/gpio/export
-bash: echo: write error: Invalid argument
echo 497 > /sys/class/gpio/export
-bash: echo: write error: Invalid argument
tung@ubuntu:~$ /sys/class/gpio/gpio496
bash: /sys/class/gpio/gpio496: No such file or directory

Very odd.

Were you using the very same device in both tests? And did you try with
the older kernel before the new one? Perhaps the new settings had not
yet taken effect otherwise?

quoted

I just did a quick test using the code in the usb-next (testing)
branch and it seems to work as expected when hard-coding alternate
functions for some of >the pins in the driver.

I did not actually reprogram the device so perhaps something is
broken with regards to reading the port configuration. But then you
should see the >problem if you apply the patch to an earlier kernel
as well.

Can you apply the below patch on top of Greg's usb-next (or
usb-testing) branch and send me the logs from when connecting the
device?

The log written is:
[ 3599.781531] cp210x 2-2.1:1.0: cp2108_gpio_init - 03 00 00 00

Thanks for confirming. So everything appears to work as expected, and
you should have seen the expected -EINVAL unless the device actually did
return all-zero here for some reason.

Johan