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Date:   Fri, 4 Feb 2022 12:06:52 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Vitaly Chikunov <vt@altlinux.org>
Cc:     linux-hyperv@vger.kernel.org,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Long Li <longli@microsoft.com>
Subject: Re: [PATCH v2] drivers: hv: vmbus: Fix build on Clang 12 failed by
 DMA_BIT_MASK(64) expansion
Message-ID: <20220204120652.h6powkl2cwsjhe2d@liuwe-devbox-debian-v2>
References: <20220204022627.4183515-1-vt@altlinux.org>
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On Fri, Feb 04, 2022 at 05:26:27AM +0300, Vitaly Chikunov wrote:
> Clang 12.0.1 cannot understand that value 64 is excluded from the shift
> at compile time (for use in global context) resulting in build error[1]:
> 
>   drivers/hv/vmbus_drv.c:2082:29: error: shift count >= width of type [-Werror,-Wshift-count-overflow]
>   static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
> 			      ^~~~~~~~~~~~~~~~
>   ./include/linux/dma-mapping.h:76:54: note: expanded from macro 'DMA_BIT_MASK'
>   #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> 						       ^ ~~~
> 
> Avoid using DMA_BIT_MASK macro for that corner case.
> 
> Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>
> Cc: Michael Kelley <mikelley@microsoft.com>
> Cc: Long Li <longli@microsoft.com>
> Cc: Wei Liu <wei.liu@kernel.org>
> Link: https://lore.kernel.org/linux-hyperv/20220203235828.hcsj6najsl7yxmxa@altlinux.org/

BTW there is no need to put in a Link tag here. The tool I use (b4)
handles this automatically.

Wei.