Re: [PATCH v3 02/22] arm64: Generate sign macro for sysreg Enums

Colton Lewis
2025-06-30T17:42:53Z

Oliver Upton <oliver.upton@linux.dev> writes:

> On Fri, Jun 27, 2025 at 08:45:38PM +0000, Colton Lewis wrote:
>> Hi Ben. Thanks for the review.

>> Ben Horgan <ben.horgan@arm.com> writes:

>> > Hi Colton,

>> > On 6/26/25 21:04, Colton Lewis wrote:
>> > > There's no reason Enums shouldn't be equivalent to UnsignedEnums and
>> > > explicitly specify they are unsigned. This will avoid the annoyance I
>> > > had with HPMN0.
>> > An Enum can be annotated with the field's sign by updating it to
>> > UnsignedEnum or SignedEnum. This is explained in [1].

>> > With this change ID_AA64PFR1_EL1.MTE_frac would be marked as unsigned
>> > when it should really be considered signed.

>> > Enum 43:40 MTE_frac
>> > 0b0000 ASYNC
>> > 0b1111 NI
>> > EndEnum

>> Thanks for the explanation. I made this a separate commit because I
>> considered people might object and HPMN0 is already an UnsignedEnum in
>> my previous commit.

>> Do you think it would be a good idea to make plain Enums signed by
>> default or should I just remove this commit from the series?

> It is presumptive to associate a sign with an enumeration. Generally
> speaking, the only fields that can do signed / unsigned comparisons are
> the Feature ID register fields.

> So please drop this and only keep the change for HPMN0.

Done.

> Thanks,
> Oliver

>> > > Signed-off-by: Colton Lewis <coltonlewis@google.com>
>> > > ---
>> > > arch/arm64/tools/gen-sysreg.awk | 1 +
>> > > 1 file changed, 1 insertion(+)

>> > > diff --git a/arch/arm64/tools/gen-sysreg.awk
>> > > b/arch/arm64/tools/gen-sysreg.awk
>> > > index f2a1732cb1f6..fa21a632d9b7 100755
>> > > --- a/arch/arm64/tools/gen-sysreg.awk
>> > > +++ b/arch/arm64/tools/gen-sysreg.awk
>> > > @@ -308,6 +308,7 @@ $1 == "Enum" && (block_current() == "Sysreg" ||
>> > > block_current() == "SysregFields
>> > > parse_bitdef(reg, field, $2)

>> > > define_field(reg, field, msb, lsb)
>> > > + define_field_sign(reg, field, "false")

>> > > next
>> > > }

>> > Thanks,

>> > Ben

>> > [1]
>> >
>> https://lore.kernel.org/all/20221207-arm64-sysreg-helpers-v4-1-25b6b3fb9d18@kernel.org/