linux-kernel - Re: [PATCH net v1 1/1] bnx2: Fix unused data compilation warning

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Message-ID: <5ec0a2cc-e5f6-42dd-992c-79b1a0c1b9f5@redhat.com>
Date: Tue, 4 Mar 2025 12:39:40 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Rasesh Mody <rmody@...vell.com>, GR-Linux-NIC-Dev@...vell.com,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net v1 1/1] bnx2: Fix unused data compilation warning

On 3/4/25 11:56 AM, Andy Shevchenko wrote:
> On Mon, Mar 03, 2025 at 05:21:14PM -0800, Jakub Kicinski wrote:
>> On Fri, 28 Feb 2025 12:05:37 +0200 Andy Shevchenko wrote:
>>> In some configuration, compilation raises warnings related to unused
>>> data. Indeed, depending on configuration, those data can be unused.
>>>
>>> Mark those data as __maybe_unused to avoid compilation warnings.
>>
>> Will making dma_unmap_addr access the first argument instead of
>> pre-processing down to nothing not work?
> 
> I looked at the implementation of those macros and I have no clue
> how to do that in a least intrusive way. Otherwise it sounds to me
> quite far from the scope of the small compilation error fix that
> I presented here.

I *think* Jakub is suggesting something alike:

---
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index b79925b1c433..927884f10b0f 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -629,7 +629,7 @@ 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(PTR, ADDR_NAME)           (((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)
---

Would that work?

Thanks,

Paolo