Re: [PATCH v2] checkpatch: Don't emit warnings for ID-base USB & PCI DT compatibles

[Chen-Yu Tsai]

Hi Andy, Joe,

On Thu, May 21, 2026 at 7:26 AM Brian Norris <briannorris@xxxxxxxxxxxx> wrote:
>
> Hi Chen-Yu,
>
> On Wed, May 20, 2026 at 04:44:27PM +0800, Chen-Yu Tsai wrote:
> > The USB and PCI device bindings define some compatible patterns based
> > on device IDs that use the comma to separate vendor and product IDs.
> >
> > These prefix patterns include:
> >
> >   - ^usb(if)?[0-9a-f]{1,4},
> >   - ^pci[0-9a-f]{2,4},
> >   - ^pciclass,
> >
> > These are not real vendor prefixes. Don't emit warnings for them.
> > Instead just skip over the DT compatible check altogether, and leave
> > the real check to the DT validator. This avoids false positive warnings
> > about undocumented DT vendor prefixes and compatibles.
> >
> > Note that the script mostly only checks the first compatible string of
> > each node, as it processes the source file line-by-line, and the check
> > only matches on the line with 'compatible = "..."'. Otherwise there
> > would be more warnings from arch/mips/boot/dts/loongson/ls7a-pch.dtsi
> > since that file also includes compatibles like "pciclass0c0310" and
> > "pciclass0c03" which are not accepted either.
>
> Looking at IEEE Std 1275-1994 (PCI Bus Binding), you're right, that's
> incorrect.
>
> > "pci0014,7a24.0" is not
> > valid either,
>
> It's possible that's trying to follow the "pciVVVV,DDDD.RR" format
> mentioned in the spec, although it's not clear if it should require 2
> digits after the dot/period. Notably, the dt-schema does *not* include
> the "dot" option at all, so maybe there's room for improvement.
>
> Anyway, that just adds to why this is a good choice:
>
> > but this patch leaves the real check to the DT validator.
>
> > Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> > ---
> > Changes since v1:
> > - Moved check earlier and match against full compatible string to avoid
> >   false positives for undocumented compatibles as well
> > - Added comma to patterns as they are now matched against the full
> >   compatible string
> > - Fixed patterns in commit message to just cover the prefix portion
> >
> > This is a simplified version of what Brian Norris previously posted [1],
> > but more comprehensive and more perl-y than what Yingying Tang posted
> > [2], which only covered the second pattern.
> >
> > This is based on next-20260519.
> >
> > Also, odd observation: the other regex patterns in this script escape
> > the comma ',', but AFAIK this is not needed.
> >
> > [1] https://lore.kernel.org/all/20190223022440.146915-1-briannorris@xxxxxxxxxxxx/
> > [2] https://lore.kernel.org/all/20251210073812.1380803-1-yingying.tang@xxxxxxxxxxxxxxxx/
> > ---
> >  scripts/checkpatch.pl | 6 ++++++
> >  1 file changed, 6 insertions(+)
>
> Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx>
> Tested-by: Brian Norris <briannorris@xxxxxxxxxxxx>

Ping on this patch.

> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index 0d18771f1b01..d4ee9d88ad07 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -3783,6 +3783,12 @@ sub process {
> >                       my $vp_file = $dt_path . "vendor-prefixes.yaml";
> >
> >                       foreach my $compat (@compats) {
> > +                             # Skip ID-based PCI and USB compatible patterns.
> > +                             # DT validation will check them properly.
> > +                             next if $compat =~ /^pciclass,/;
> > +                             next if $compat =~ /^pci[a-f0-9]{2,4},/;
> > +                             next if $compat =~ /^usb(if)?[a-f0-9]{1,4},/;
> > +
> >                               my $compat2 = $compat;
> >                               $compat2 =~ s/\,[a-zA-Z0-9]*\-/\,<\.\*>\-/;
> >                               my $compat3 = $compat;
> > --
> > 2.54.0.631.ge1b05301d1-goog
> >