Re: [Xen-devel] [PATCH v2 01/12] pci: introduce a devfn field to pci_sbdf_t

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Jun 06, 2019 at 04:09:31AM -0600, Jan Beulich wrote:
> >>> On 06.06.19 at 11:50, <Paul.Durrant@xxxxxxxxxx> wrote:
> >>  -----Original Message-----
> >> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf 
> >> Of 
> > Roger Pau Monne
> >> Sent: 06 June 2019 10:02
> >> To: xen-devel@xxxxxxxxxxxxxxxxxxxx 
> >> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; 
> >> Konrad 
> > Rzeszutek Wilk
> >> <konrad.wilk@xxxxxxxxxx>; George Dunlap <George.Dunlap@xxxxxxxxxx>; Andrew 
> > Cooper
> >> <Andrew.Cooper3@xxxxxxxxxx>; Ian Jackson <Ian.Jackson@xxxxxxxxxx>; Tim 
> >> (Xen.org) 
> > <tim@xxxxxxx>; Julien
> >> Grall <julien.grall@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Roger Pau 
> >> Monne 
> > <roger.pau@xxxxxxxxxx>
> >> Subject: [Xen-devel] [PATCH v2 01/12] pci: introduce a devfn field to 
> > pci_sbdf_t
> >> 
> >> This is equivalent to the current extfunc field in term of contents.
> >> 
> >> Switch the two current users of extfunc to use devfn instead for
> >> correctness.
> >> 
> >> No functional change.
> >> 
> >> Requested-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> >> ---
> >> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> >> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> >> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> >> Cc: Julien Grall <julien.grall@xxxxxxx>
> >> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> >> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >> Cc: Tim Deegan <tim@xxxxxxx>
> >> Cc: Wei Liu <wl@xxxxxxx>
> >> ---
> >> Changes since v1:
> >>  - New in this version.
> >> ---
> >> NB: Paul suggested to name the function field fn instead of func, so
> >> that it would match the naming of the devfn field. Sadly the func
> >> field cannot be aliased to another field using a union because it's a
> >> bit field, so the only option is to rename func to fn.
> > 
> > Is that true? Can you not do something like...
> > 
> > union {
> >   struct {
> >     uint8_t func : 3,
> >             dev  : 5;
> >   };
> >   struct {
> >     uint8_t fn   : 3,
> >             pad  : 5;
> 
> And the "pad" field here wouldn't really be necessary.
> 
> Is there a reason "func" needs to be kept? If so, is there a plan to
> phase out its use? If so, perhaps fn and dev should be grouped
> together, and func should become the (temporary) alias?

I think I can prepare a pre-patch to rename func to fn, the users of
pci_sbdf_t are very limited at this point. If you agree with this I
will add such a patch at the beginning of the series.

Thanks, Roger.

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