Re: [PATCH] Enable legacy support for serial ports when SERIAL_8250_PNP is disabled

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On 7/9/07, Bjorn Helgaas <[email protected]> wrote:
On Saturday 07 July 2007 05:33:00 pm Luca Tettamanti wrote:
> your patch:
>
> commit 7e92b4fc345f5b6f57585fbe5ffdb0f24d7c9b26
> Author: Bjorn Helgaas <[email protected]>
> Date:   Tue May 8 00:36:07 2007 -0700
>
>     x86, serial: convert legacy COM ports to platform devices
>
> disables probing using legacy code in favour of ACPI/PNP to avoid double
> discovery.
>
> However if SERIAL_8250_PNP is not enabled the user is left without
> serial ports (been there, done that - my kernel config suddenly wasn't
> working anymore). So:

Yes, that's true.  Kconfig should automatically turn on SERIAL_8250_PNP
if PNP and SERIAL_8250 are selected, but it does give you a choice if
you have EMBEDDED set.  So I guess you must have this:

  CONFIG_EMBEDDED=y
  CONFIG_PNP=y
  CONFIG_SERIAL_8250=y
  CONFIG_SERIAL_8250_PNP=n

Why do you want PNP support, but not 8250_PNP support?

That's a good question :-) IIRC the serial PNP code used to mess up
the mode of the port on my laptop, making it useless for debugging the
boot. Bug was fixed long ago, but I didn't re-enabled that option.

If you turn off
PNP completely, you will have "pnp_platform_devices == 0", and the
existing code will do what you need.

Well for me it's a non-issue, I'm able to "work-around" it in many
ways. My point is that a configuration that used to work and is still
valid suddenly doesn't work anymore. I missed the dependacy on
CONFIG_EMBEDDED though, so feel free to ignore the patch ;-)

Luca
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