Re: [PATCH v5 03/34] ACPI / PPTT: Add acpi_pptt_cache_v1_full to use pptt cache as one structure

[Fenghua Yu]

On 11/18/25 02:57, Ben Horgan wrote:
> Hi Fenghua,
>
> On 11/18/25 04:03, Fenghua Yu wrote:
> > Hi, Ben,
> >
> > On 11/17/25 08:59, Ben Horgan wrote:
> > > In actbl2.h, acpi_pptt_cache describes the fields in the original
> > > Cache Type Structure. In PPTT table version 3 a new field was added at
> > > the
> > > end, cache_id. This is described in acpi_pptt_cache_v1 but rather than
> > > including all v1 fields it just includes this one.
> > >
> > > In lieu of this being fixed in acpica, introduce
> > > acpi_pptt_cache_v1_full to
> > > contain all the fields of the Cache Type Structure . Update the existing
> > > code to use this new struct. This simplifies the code and removes a
> > > non-standard use of ACPI_ADD_PTR.
> > >
> > > Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
> > > ---
> > > I have opened a pull request to acpica to update acpi_pptt_cache_v1 to
> > > include all fields. https://github.com/acpica/acpica/pull/1059
> > >
> > > Change since v4:
> > > Use fields directly in acpi_pptt_cache_v1_full
> > > Delay the casting
> > >
> > > Changes since v3:
> > > New patch
> > > ---
> > >    drivers/acpi/pptt.c | 47 +++++++++++++++++++++++++++++++++++----------
> > >    1 file changed, 37 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> > > index 2856254e29d7..53fde9bd8140 100644
> > > --- a/drivers/acpi/pptt.c
> > > +++ b/drivers/acpi/pptt.c
> > > @@ -21,6 +21,25 @@
> > >    #include <linux/cacheinfo.h>
> > >    #include <acpi/processor.h>
> > >    +/*
> > > + * The acpi_pptt_cache_v1 in actbl2.h, which is imported from acpica,
> > > + * only contains the cache_id field rather than all the fields of the
> > > + * Cache Type Structure. Use this alternative structure until it is
> > > + * resolved in acpica.
> > > + */
> > > +struct acpi_pptt_cache_v1_full {
> > > +    struct acpi_subtable_header header;
> > > +    u16 reserved;
> > > +    u32 flags;
> > > +    u32 next_level_of_cache;
> > > +    u32 size;
> > > +    u32 number_of_sets;
> > > +    u8 associativity;
> > > +    u8 attributes;
> > > +    u16 line_size;
> > > +    u32 cache_id;
> > > +};
> >
> > Should "__packed" be added to this table?
>
> Yes, I missed that.

With this fixed,

Reviewed-by: Fenghua Yu <fenghuay@xxxxxxxxxx>

> > Should this table be defined in include/acpi/actbl2.h? Seems defining
> > the two cache tables separately in two places are not natural?
>
> Indeed. The dificulty is that include/acpi/actbl2.h is generated from
> acpica. I propose a fix for this in the  pull request mentioned above:
> https://github.com/acpica/acpica/pull/1059 This extends
> acpi_pptt_cache_v1 to include all the fields in the new version of the
> cache type structure (not just cache_id).
>
> One thing I could do if it looks like the acpica change will be accepted
> is to temporarily delete acpi_pptt_cache_v1 from include/acpi/actbl2.h
> and rename acpi_pptt_cache_v1_full in drivers/acpi/pptt.c to
> acpi_pptt_cache_v1. When include/acpi/actbl2.h is updated the conflict
> should be evident and the version in drivers/acpi/pptt.c can be dropped.
>   I'll keep it like it is for now though as this would be an api breaking
> change for acpica and the maintainers may prefer to handle this a
> different way.

Right. Thank you for your explanation!

-Fenghua