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Re: [XEN RFC PATCH 04/40] xen/arm: return default DMA bit width when platform is not set
- To: Wei Chen <Wei.Chen@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 13 Aug 2021 08:56:00 +0200
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- Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>, "julien@xxxxxxx" <julien@xxxxxxx>
- Delivery-date: Fri, 13 Aug 2021 06:56:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.08.2021 08:54, Wei Chen wrote:
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 2021年8月11日 18:54
>>
>> On 11.08.2021 12:23, Wei Chen wrote:
>>> --- a/xen/arch/arm/platform.c
>>> +++ b/xen/arch/arm/platform.c
>>> @@ -27,6 +27,7 @@ extern const struct platform_desc _splatform[],
>> _eplatform[];
>>> /* Pointer to the current platform description */
>>> static const struct platform_desc *platform;
>>>
>>> +extern unsigned int dma_bitsize;
>>
>> This is a no-go: Declarations need to live in a header which the producer
>> and all consumers include. Else ...
>
> Ok, I will place it to a header.
>
>>
>>> --- a/xen/common/page_alloc.c
>>> +++ b/xen/common/page_alloc.c
>>> @@ -227,7 +227,7 @@ static bool __read_mostly scrub_debug;
>>> * Bit width of the DMA heap -- used to override NUMA-node-first.
>>> * allocation strategy, which can otherwise exhaust low memory.
>>> */
>>> -static unsigned int dma_bitsize;
>>> +unsigned int dma_bitsize;
>>
>> ... a change here (of e.g. the type) will go unnoticed by the compiler,
>> and the consumer of the variable may no longer work correctly.
>>
>
> Sorry, I am not very clear about this comment.
I've merely been trying to explain _why_ the declaration needs to be
in a header.
Jan
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