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Message-ID: <00bf258587510ee96a27918293bd4d75622512c6.camel@perches.com>
Subject: Re: [RFC PATCH] checkpatch: check for function calls with struct or
 union on stack
From:   Joe Perches <joe@perches.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Andy Whitcroft <apw@canonical.com>,
        LKML <linux-kernel@vger.kernel.org>
Date:   Thu, 26 Jul 2018 13:05:29 -0700
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         <20180726122533.104f6eea950853ef50ebc680@linux-foundation.org>
         <20180726122807.fad0566951e36d930edb6874@linux-foundation.org>
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On Thu, 2018-07-26 at 12:28 -0700, Andrew Morton wrote:
> On Thu, 26 Jul 2018 12:25:33 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > I'll give it a spin, see how noisy it is.
> 
> Actually, I would prefer if the message, changelog and title
> used the term "passed by value".  It's a more familiar term
> and it is possible for a passed-by-value aggregate to in fact 
> be passed in registers.

RFC, No worries, I'll change it if it's OK.

I'm testing it right now against the last 5000 commits
(which takes awhile here) via

$ git log --no-merges --format=oneline -5000 | \
  cut -f1 -d" " | \
  while read commit ; do \
    echo $commit; \
    ./scripts/checkpatch.pl --git $commit --types=aggregate_on_stack --quiet --no-summary ; \
  done

It doesn't seem noisy at all, but maybe there are a few
known structs like "struct timespec64" that could be
excluded.

The only real hits so far are:

commit f2fb56afba11426ee5c9603b28a9827c530909c0
WARNING: Unusual use of 'struct msm_display_topology' on stack
#28374: FILE: drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c:149:
+enum dpu_rm_topology_name
+dpu_rm_get_topology_name(struct msm_display_topology topology)
+{

WARNING: Unusual use of 'struct msm_display_topology' on stack
#29021: FILE: drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c:796:
+static int _dpu_rm_populate_requirements(
+		struct dpu_rm *rm,
+		struct drm_encoder *enc,
+		struct drm_crtc_state *crtc_state,
+		struct drm_connector_state *conn_state,
+		struct dpu_rm_requirements *reqs,
+		struct msm_display_topology req_topology)
+{

WARNING: Unusual use of 'struct msm_display_topology' on stack
#29203: FILE: drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c:978:
+int dpu_rm_reserve(
+		struct dpu_rm *rm,
+		struct drm_encoder *enc,
+		struct drm_crtc_state *crtc_state,
+		struct drm_connector_state *conn_state,
+		struct msm_display_topology topology,
+		bool test_only)
+{

WARNING: Unusual use of 'struct msm_display_topology' on stack
#29443: FILE: drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h:133:
+int dpu_rm_reserve(struct dpu_rm *rm,
+		struct drm_encoder *drm_enc,
+		struct drm_crtc_state *crtc_state,
+		struct drm_connector_state *conn_state,
+		struct msm_display_topology topology,
+		bool test_only);

WARNING: Unusual use of 'struct msm_display_topology' on stack
#29506: FILE: drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h:196:
+enum dpu_rm_topology_name
+dpu_rm_get_topology_name(struct msm_display_topology topology);

and

33477d84c26bbfa626da2c032e567a90dd70a528
WARNING: Unusual use of 'struct cppc_perf_fb_ctrs' on stack
#45: FILE: drivers/cpufreq/cppc_cpufreq.c:307:
+static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu,
+				     struct cppc_perf_fb_ctrs fb_ctrs_t0,
+				     struct cppc_perf_fb_ctrs fb_ctrs_t1)
+{

WARNING: Unusual use of 'struct cppc_perf_fb_ctrs' on stack
#45: FILE: drivers/cpufreq/cppc_cpufreq.c:307:
+static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu,
+				     struct cppc_perf_fb_ctrs fb_ctrs_t0,
+				     struct cppc_perf_fb_ctrs fb_ctrs_t1)
+{