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Re: [PATCH V4 14/24] arm/ioreq: Introduce arch specific bits for IOREQ/DM features

On 27.01.2021 13:22, Oleksandr wrote:
> On 27.01.21 12:24, Jan Beulich wrote:
>> On 21.01.2021 09:50, Oleksandr wrote:
>>> On 20.01.21 17:50, Julien Grall wrote:
>>>> On 17/01/2021 18:52, Oleksandr wrote:
>>>>> error2.txt - when add #include <public/hvm/dm_op.h> to xen/ioreq.h
>>>> It looks like the error is happening in dm.c rather than xen/dm.h. Any
>>>> reason to not include <public/hvm/dm_op.h> in dm.c directly?
>>> Including it directly doesn't solve build issue.
>>> If I am not mistaken in order to follow requirements how to include
>>> headers (alphabetic order, public* should be included after xen* and
>>> asm* ones, etc)
>>> the dm.h gets included the first in dm.c, and dm_op.h gets included the
>>> last. We can avoid build issue if we change inclusion order a bit,
>>> what I mean is to include dm.h after hypercall.h at least (because
>>> hypercall.h already includes dm_op.h). But this breaks the requirements
>>> and is not way to go.
>>> Now I am in doubt how to overcome this.
>> First, violating the alphabetic ordering rule is perhaps less
>> of a problem than putting seemingly stray #include-s anywhere.
>> However, as soon as ordering starts mattering, this is
>> indicative of problems with the headers: Either the (seemingly)
>> too early included one lacks some #include-s, or you've run
>> into a circular dependency. In the former case the needed
>> #include-s should be added, and all ought to be fine. In the
>> latter case, however, disentangling may be a significant
>> effort, and hence it may be sensible and acceptable to instead
>> use unusual ordering of #include-s in the one place where it
>> matters (suitably justified in the description). Ideally such
>> would come with a promise to try to sort this later on, when
>> time is less constrained.
> Thank you for the explanation. I think, I am facing the former case (too 
> early included one lacks some #include-s),
> actually both common/dm.c and arch/arm/dm.c suffer from that.
> It works for me if I add the following to both files (violating the 
> alphabetic ordering rule):
> +#include <xen/types.h>
> +#include <public/hvm/dm_op.h>
> +
>   #include <xen/dm.h>
> So, if I got your point correctly, we could include these both headers 
> by dm.h) Would it be appropriate (with suitable justification of course)?

Perhaps - this is a header you introduce aiui, so it's up to
you to arrange for it to include all further headers it
depends upon. In such a case (new header) you don't need to
explicitly justify what you include, but of course you don't
want to include excessive ones, or you risk getting back
"Why?" from reviewers.




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