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

[Paolo Bonzini <pbonzini@redhat.com>]

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.

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)

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

- 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)
>