linux-kernel - [PATCH v2 3/5] drivers/core: simplify variadic args handling

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Message-Id: <20251201-va_format_call-v2-3-2906f3093b60@intel.com>
Date: Mon, 01 Dec 2025 10:31:24 +0100
From: Andrzej Hajda <andrzej.hajda@...el.com>
To: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
 John Ogness <john.ogness@...utronix.de>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>, 
 Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, 
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>, 
 Brendan Jackman <jackmanb@...gle.com>, Johannes Weiner <hannes@...xchg.org>, 
 Zi Yan <ziy@...dia.com>, Christoph Lameter <cl@...two.org>, 
 David Rientjes <rientjes@...gle.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
 Andrzej Hajda <andrzej.hajda@...el.com>
Subject: [PATCH v2 3/5] drivers/core: simplify variadic args handling

Changing argument type from va_list to struct va_format * allows
to simplify variadic argument handling with va_format_call helper.

Signed-off-by: Andrzej Hajda <andrzej.hajda@...el.com>
---
 drivers/base/core.c | 50 +++++++-------------------------------------------
 1 file changed, 7 insertions(+), 43 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 513e5ef8a6da..4d76b67a87e3 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4965,30 +4965,12 @@ define_dev_printk_level(_dev_info, KERN_INFO);
 #endif
 
 static void __dev_probe_failed(const struct device *dev, int err, bool fatal,
-			       const char *fmt, va_list vargsp)
+			       const char *fmt, struct va_format *vaf)
 {
-	struct va_format vaf;
-	va_list vargs;
-
-	/*
-	 * On x86_64 and possibly on other architectures, va_list is actually a
-	 * size-1 array containing a structure.  As a result, function parameter
-	 * vargsp decays from T[1] to T*, and &vargsp has type T** rather than
-	 * T(*)[1], which is expected by its assignment to vaf.va below.
-	 *
-	 * One standard way to solve this mess is by creating a copy in a local
-	 * variable of type va_list and then using a pointer to that local copy
-	 * instead, which is the approach employed here.
-	 */
-	va_copy(vargs, vargsp);
-
-	vaf.fmt = fmt;
-	vaf.va = &vargs;
-
 	switch (err) {
 	case -EPROBE_DEFER:
-		device_set_deferred_probe_reason(dev, &vaf);
-		dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+		device_set_deferred_probe_reason(dev, vaf);
+		dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), vaf);
 		break;
 
 	case -ENOMEM:
@@ -4998,13 +4980,11 @@ static void __dev_probe_failed(const struct device *dev, int err, bool fatal,
 	default:
 		/* Log fatal final failures as errors, otherwise produce warnings */
 		if (fatal)
-			dev_err(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+			dev_err(dev, "error %pe: %pV", ERR_PTR(err), vaf);
 		else
-			dev_warn(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+			dev_warn(dev, "error %pe: %pV", ERR_PTR(err), vaf);
 		break;
 	}
-
-	va_end(vargs);
 }
 
 /**
@@ -5042,15 +5022,7 @@ static void __dev_probe_failed(const struct device *dev, int err, bool fatal,
  */
 int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
 {
-	va_list vargs;
-
-	va_start(vargs, fmt);
-
-	/* Use dev_err() for logging when err doesn't equal -EPROBE_DEFER */
-	__dev_probe_failed(dev, err, true, fmt, vargs);
-
-	va_end(vargs);
-
+	va_format_call(fmt, __dev_probe_failed, dev, err, true, fmt, va_format_arg);
 	return err;
 }
 EXPORT_SYMBOL_GPL(dev_err_probe);
@@ -5090,15 +5062,7 @@ EXPORT_SYMBOL_GPL(dev_err_probe);
  */
 int dev_warn_probe(const struct device *dev, int err, const char *fmt, ...)
 {
-	va_list vargs;
-
-	va_start(vargs, fmt);
-
-	/* Use dev_warn() for logging when err doesn't equal -EPROBE_DEFER */
-	__dev_probe_failed(dev, err, false, fmt, vargs);
-
-	va_end(vargs);
-
+	va_format_call(fmt, __dev_probe_failed, dev, err, false, fmt, va_format_arg);
 	return err;
 }
 EXPORT_SYMBOL_GPL(dev_warn_probe);

-- 
2.43.0