Re: [Qemu-devel] [qemu-s390x] [PATCH 1/1] 390x/cpumodel: document S390FeatDef.bit not applicable

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 20 Feb 2018 17:08:52 +0100
David Hildenbrand <david@redhat.com> wrote:

> On 20.02.2018 17:07, Cornelia Huck wrote:
> > On Tue, 20 Feb 2018 17:04:19 +0100
> > Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> >   
> >> On 02/20/2018 04:55 PM, David Hildenbrand wrote:  
> >>> On 20.02.2018 16:53, Cornelia Huck wrote:    
> >>>> On Tue, 20 Feb 2018 16:07:13 +0100
> >>>> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
> >>>>    
> >>>>> The 'bit' field of the 'S390FeatDef' structure is not applicable to all
> >>>>> it's instances. Currently a this field is not applicable, and remains    
> >>>>
> >>>> s/it's/its/
> >>>>
> >>>> s/a this/this/
> >>>>    
> >>>>> unused, iff the feature is of type S390_FEAT_TYPE_MISC. Having the value 0
> >>>>> specified for multiple such feature definition  was a little confusing,
> >>>>> as it's a perfectly legit bit value, and as usually the value of the bit
> >>>>> field is ought to be unique for each feature.
> >>>>>
> >>>>> Let's document this, and hopefully reduce the potential for confusion.
> >>>>>
> >>>>> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> >>>>> ---
> >>>>>
> >>>>> Hi!
> >>>>>
> >>>>> This may be an overkill. A comment where the misc features
> >>>>> are defined would do to, but I think this is nicer. So
> >>>>> I decided to try it with this approach first.    
> >>>>
> >>>> Is there likely to be anything else than FEAT_MISC _not_ using .bit? If
> >>>> not, would it be better to at a comment to the FEAT_MISC definition?    
> >>>
> >>> Doubt it right now. I would sign the "overkill" part :)    
> >>
> >> I can cconfirm that this code caused some questions and it took me some
> >> minutes to remember why 0 and 0 was ok. So I certainly want to have a comment
> >> of some form.
> >>  
> > 
> > I'd prefer a comment about FEAT_MISC usage rather than a magic value.
> >   
> 
> We can also add FEAT_INIT_MISC. And add a comment in the initializer.
> 

That's what I like best.