linux-kernel - Re: [PATCH 29/33] serial: 8250: drop DEBUG

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Message-ID: <alpine.DEB.2.21.2506171216090.37405@angie.orcam.me.uk>
Date: Tue, 17 Jun 2025 12:32:48 +0100 (BST)
From: "Maciej W. Rozycki" <macro@...am.me.uk>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
    Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 29/33] serial: 8250: drop DEBUG_AUTOCONF() macro

On Wed, 11 Jun 2025, Jiri Slaby (SUSE) wrote:

> DEBUG_AUTOCONF() is always disabled (by "#if 0"), so one would need to
> recompile the kernel to use it. And even if they did, they would find
> out it is broken anyway:
>   error: variable 'scratch' is used uninitialized whenever 'if' condition is false

 This is removing useful debugging aids.

 The issue with compilation is related to commit 3398cc4f2b15 ("serial: 
8250: Add IIR FIFOs enabled field properly"), which removed the assignment 
of IIR to `scratch' (although a path did exist before it that bypassed the 
assignment anyway), and can be trivially fixed by bringing the assignment 
back and moving the debug statement next to it.

 I agree that "#if 0" isn't very useful as it requires patching the source 
to activate; changing it to "#ifdef DEBUG" would make more sense nowadays.

  Maciej