Re: [PATCH net] gve: DQO: Suppress unused var warnings

On Mon, Sep 27, 2021 at 4:21 PM Jakub Kicinski [off-list ref] wrote:

On Mon, 27 Sep 2021 13:21:30 -0700 Bailey Forrest wrote:

quoted

Apologies, resending as text

On Mon, Sep 27, 2021 at 2:59 AM Arnd Bergmann [off-list ref] wrote:

quoted

On Sat, Jul 24, 2021 at 1:19 AM Bailey Forrest [off-list ref] wrote:

quoted

Some variables become unused when `CONFIG_NEED_DMA_MAP_STATE=n`.

We only suppress when `CONFIG_NEED_DMA_MAP_STATE=n` in order to avoid
false negatives.

Fixes: a57e5de476be ("gve: DQO: Add TX path")
Signed-off-by: Bailey Forrest <redacted>

Hi Bailey,

I see that the warning still exists in linux-5.15-rc3 and net-next,
I'm building with my original patch[1] to get around the -Werror
warnings.

Can you resend your patch, or should I resend mine after all?

      Arnd

[1] https://lore.kernel.org/all/20210721151100.2042139-1-arnd@kernel.org/ (local)

Hi David/Jakub,

Any thoughts on my patch? I'm open to alternative suggestions for how
to resolve this.

This patch still works and merges cleanly on HEAD.

Looks like fixing this on the wrong end, dma_unmap_len_set()
and friends should always evaluate their arguments.

That makes sense.

Arnd, if you want to fix this inside of the dma_* macros, the
following diff resolves the errors reported for this driver:

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index dca2b1355bb1..f51eee0f678e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h

@@ -590,10 +590,21 @@ static inline int dma_mmap_wc(struct device *dev,
 #else
 #define DEFINE_DMA_UNMAP_ADDR(ADDR_NAME)
 #define DEFINE_DMA_UNMAP_LEN(LEN_NAME)
-#define dma_unmap_addr(PTR, ADDR_NAME)           (0)
-#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL)  do { } while (0)
-#define dma_unmap_len(PTR, LEN_NAME)             (0)
-#define dma_unmap_len_set(PTR, LEN_NAME, VAL)    do { } while (0)
+
+#define dma_unmap_addr(PTR, ADDR_NAME) ({ (void)PTR; 0; })
+
+#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL) do { \
+ (void)PTR; \
+ (void)VAL; \
+} while (0)
+
+#define dma_unmap_len(PTR, LEN_NAME) ({ (void)PTR; 0; })
+
+#define dma_unmap_len_set(PTR, LEN_NAME, VAL) do { \
+ (void)PTR; \
+ (void)VAL; \
+} while (0)
+
 #endif

 #endif /* _LINUX_DMA_MAPPING_H */