[PATCH] coresight: catu: fix clang build warning

[PATCH] coresight: catu: fix clang build warning

[Arnd Bergmann]

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@arndb.de>
---
 drivers/hwtracing/coresight/coresight-catu.h    | 5 -----
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 4 ++--
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-catu.h b/drivers/hwtracing/coresight/coresight-catu.h
index 1b281f0dcccc..1d2ad183fd92 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 f684283890d3..6378c3dece6b 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -772,7 +772,7 @@ 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,
@@ -786,7 +786,7 @@ 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)
-- 
2.20.0

Re: [PATCH] coresight: catu: fix clang build warning

[Suzuki K Poulose]

Hi Arnd,

On 07/03/2019 10:32, Arnd Bergmann wrote:
> 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@arndb.de>

Thanks for the fix.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Re: [PATCH] coresight: catu: fix clang build warning

[Mathieu Poirier]

On Thu, 7 Mar 2019 at 03:48, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> Hi Arnd,
>
> On 07/03/2019 10:32, Arnd Bergmann wrote:
> > 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@arndb.de>
>
> Thanks for the fix.
>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Applied after fixing line over 80 characters.

Thanks,
Mathieu