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Re: [Xen-devel] Re: [patch/rfc] multiprotocol blkback drivers (32-on-64)

  • To: Gerd Hoffmann <kraxel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>
  • From: Keir Fraser <keir@xxxxxxxxxxxxx>
  • Date: Tue, 19 Dec 2006 14:20:21 +0000
  • Cc: Xen devel list <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Tue, 19 Dec 2006 06:20:18 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AccjeNDUD6ZqNI9sEduUXAAX8io7RQ==
  • Thread-topic: [Xen-devel] Re: [patch/rfc] multiprotocol blkback drivers (32-on-64)

On 19/12/06 13:32, "Gerd Hoffmann" <kraxel@xxxxxxx> wrote:

>> - unconditionally using #pragma pack(), __attribute__(()), and __i386__ or
>>   __x86_64__ in public Xen headers is, in my opinion, a no-go (these header
>>   should all be suitable for building e.g. Windows drivers, too - I know this
>> isn't
>>   generally the case at present, but I don't think anything else can be the
>> goal,
>>   and hence the situation shouldn't be made worse)
> Ideas for that one?  Ok to create xen/include/public/compiler.h with
> that kind of stuff in?

I think it would be reasonable to put this stuff in a (new) Linux-specific
header file that wraps the Xen-public blkif.h. We could put just enough
support in blkif.h itself to allow it to be multiply-compiled. Then
different OSes can wrap or rewrite blkif.h as they see fit to get the
required layout for 32-bit and 64-bit ABIs. This conveniently sidesteps some
of these issues and allows you to concentrate on Linux and GCC, while not
constraining the implementation choices for anyone else.

 -- Keir

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