linux-kernel - [PATCH 4.19 328/639] coresight: catu: fix clang build warning

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Date:   Fri, 24 Jan 2020 10:28:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 328/639] coresight: catu: fix clang build warning

From: Arnd Bergmann <arnd@...db.de>

[ Upstream commit 59d63de076607a9334b11628b5c3ddda1d8f56cd ]

Clang points out a syntax error, as the etr_catu_buf_ops structure is
declared 'static' before the type is known:

In file included from drivers/hwtracing/coresight/coresight-tmc-etr.c:12:
drivers/hwtracing/coresight/coresight-catu.h:116:40: warning: tentative definition of variable with internal linkage has incomplete non-array type 'const struct etr_buf_operations' [-Wtentative-definition-incomplete-type]
static const struct etr_buf_operations etr_catu_buf_ops;
                                       ^
drivers/hwtracing/coresight/coresight-catu.h:116:21: note: forward declaration of 'struct etr_buf_operations'
static const struct etr_buf_operations etr_catu_buf_ops;

This seems worth fixing in the code, so replace pointer to the empty
constant structure with a NULL pointer. We need an extra NULL pointer
check here, but the result should be better object code otherwise,
avoiding the silly empty structure.

Fixes: 434d611cddef ("coresight: catu: Plug in CATU as a backend for ETR buffer")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
[Fixed line over 80 characters]
Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hwtracing/coresight/coresight-catu.h    | 5 -----
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++--
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-catu.h b/drivers/hwtracing/coresight/coresight-catu.h
index 1b281f0dcccca..1d2ad183fd92d 100644
--- a/drivers/hwtracing/coresight/coresight-catu.h
+++ b/drivers/hwtracing/coresight/coresight-catu.h
@@ -109,11 +109,6 @@ static inline bool coresight_is_catu_device(struct coresight_device *csdev)
 	return true;
 }
 
-#ifdef CONFIG_CORESIGHT_CATU
 extern const struct etr_buf_operations etr_catu_buf_ops;
-#else
-/* Dummy declaration for the CATU ops */
-static const struct etr_buf_operations etr_catu_buf_ops;
-#endif
 
 #endif
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 2d6f428176ff8..3b684687b5a7d 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -747,7 +747,8 @@ static inline void tmc_etr_disable_catu(struct tmc_drvdata *drvdata)
 static const struct etr_buf_operations *etr_buf_ops[] = {
 	[ETR_MODE_FLAT] = &etr_flat_buf_ops,
 	[ETR_MODE_ETR_SG] = &etr_sg_buf_ops,
-	[ETR_MODE_CATU] = &etr_catu_buf_ops,
+	[ETR_MODE_CATU] = IS_ENABLED(CONFIG_CORESIGHT_CATU)
+						? &etr_catu_buf_ops : NULL,
 };
 
 static inline int tmc_etr_mode_alloc_buf(int mode,
@@ -761,7 +762,7 @@ static inline int tmc_etr_mode_alloc_buf(int mode,
 	case ETR_MODE_FLAT:
 	case ETR_MODE_ETR_SG:
 	case ETR_MODE_CATU:
-		if (etr_buf_ops[mode]->alloc)
+		if (etr_buf_ops[mode] && etr_buf_ops[mode]->alloc)
 			rc = etr_buf_ops[mode]->alloc(drvdata, etr_buf,
 						      node, pages);
 		if (!rc)
-- 
2.20.1