linux-kernel - new checkpatch flexible array test ? (was Re: [PATCH v4 12/14] gunyah: rsc

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Date:   Sun, 02 Oct 2022 18:46:30 -0700
From:   Joe Perches <joe@...ches.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Elliot Berman <quic_eberman@...cinc.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: new checkpatch flexible array test ?  (was Re: [PATCH v4 12/14]
 gunyah: rsc_mgr: Add RPC for console services)

On Fri, 2022-09-30 at 14:22 +0200, Greg Kroah-Hartman wrote:
> On Wed, Sep 28, 2022 at 12:56:31PM -0700, Elliot Berman wrote:
> > Gunyah resource manager defines a simple API for virtual machine log
> > sharing with the console service.
[]
> > diff --git a/include/linux/gunyah_rsc_mgr.h b/include/linux/gunyah_rsc_mgr.h
[]
> > +struct gh_rm_notif_vm_console_chars {
> > +	u16 vmid;
> > +	u16 num_bytes;
> > +	u8 bytes[0];
> 
> Please do not use [0] for new structures, otherwise we will just have to
> fix them up again as we are trying to get rid of all of these from the
> kernel. Just use "bytes[];" instead.

Maybe a checkpatch addition like:
---
 scripts/checkpatch.pl | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 2737e4ced5745..187ed84c1f80a 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3948,6 +3948,17 @@ sub process {
 			}
 		}
 
+# check for zero length array declarations in likely structs
+		if ($line =~ /^\+\t($Declare\s*$Ident)\s*\[\s*0\s*\]\s*;\s*$/ &&
+		    defined $lines[$linenr] &&
+		    $lines[$linenr] =~ /^[\+ ]\}\s*(?:__\w+\s*(?:$balanced_parens)?)\s*;\s*$/) {
+			if (WARN("FLEXIBLE_ARRAY_ZERO",
+				 "Prefer flexible length array declarations with [] over [0]\n" . $herecurr) &&
+			    $fix) {
+				$fixed[$fixlinenr] =~ s/\[\s*0\s*\]/[]/;
+			}
+		}
+
 # check for multiple consecutive blank lines
 		if ($prevline =~ /^[\+ ]\s*$/ &&
 		    $line =~ /^\+\s*$/ &&