Re: [RFC PATCH 4/5] hw/ppc/fdt: Drop dependency on libfdt

[David Gibson]

On Wed, May 12, 2021 at 09:59:00AM +0200, Paolo Bonzini wrote:
> On 12/05/21 04:30, David Gibson wrote:
> > On Tue, May 11, 2021 at 05:53:53PM +0200, Philippe Mathieu-Daudé wrote:
> > > hw/ppc/fdt.c defines the ppc_create_page_sizes_prop() function,
> > > which is unrelated to the libfdt. Remove the incorrect library
> > > dependency on the file.
> > > 
> > > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> > 
> > This is definitely wrong as it stands.  AFAICT this doesn't add a
> > build of hw/ppc/fdt.c anywhere, but it is definitely needed by both
> > pseries and powernv machine types, who select FDT_PPC for this exact
> > reason.
> > 
> > I will grant you that it is badly named.  It is in fact related to
> > libfdt, just rather indirectly.
> 
> The patch makes sense in general.  The file is only needed for pseries and
> powernv, not for e.g. e500 which does need fdt.

Yes, agreed.

> I would get rid of FDT_PPC completely.  First, before patch 3, you can move
> fdt.c to PSERIES and POWERNV (it's too small to need its own Kconfig symbol)
> and only leave
> 
>    ppc_ss.add(when: 'CONFIG_FDT_PPC', if_true: fdt)

Uh... why do we need even this?

> Since you are at it, remove the silly #ifdef TARGET_PPC64 in the
> hw/ppc/fdt.c file.
> 
> Then in patch 3:
> 
> - add to Kconfig.host
> 
>     config FDT
>        bool
> 
>     config LIBFDT
>        bool
>        depends on FDT

Um.. I'm not sure what semantic difference you're envisaging between
FDT and LIBFDT.

> - for all the boards I listed in my review, add "select LIBFDT" in addition
> to "depends on FDT".
> 
> - add to meson.build
> 
>     softmmu_ss.add(when: 'CONFIG_LIBFDT', if_true: fdt)
> 
> Paolo
> 
> > > ---
> > >   hw/ppc/meson.build | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
> > > index e82a6b4105b..580e6e42c8a 100644
> > > --- a/hw/ppc/meson.build
> > > +++ b/hw/ppc/meson.build
> > > @@ -3,9 +3,9 @@
> > >     'ppc.c',
> > >     'ppc_booke.c',
> > >   ))
> > > -ppc_ss.add(when: 'CONFIG_FDT_PPC', if_true: [files(
> > > +ppc_ss.add(when: 'CONFIG_FDT_PPC', if_true: files(
> > >     'fdt.c',
> > > -), fdt])
> > > +))
> > >   ppc_ss.add(when: 'CONFIG_FW_CFG_PPC', if_true: files('fw_cfg.c'))
> > >   # IBM pSeries (sPAPR)
> > 
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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