On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote: > While the list of rules may have been accurate when created, it now > lacks some clarity in the face of isa-manual updates. Specifically: > > - there is no mention here of a distinction between regular 'Z' > extensions which are "Additional Standard Extensions" and "Zxm" > extensions which are "Standard Machine-Level Extensions" > > - there is also no explicit mention of where either should be sorted in > the list > > - underscores are only required between two *multi-letter* extensions but > the list of rules implies that this is required between a multi-letter > extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a > valid string > > Attempt to clean up the list of rules, by adding information on the > above & sprinkling in some white space for readability. > > Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> > --- > arch/riscv/kernel/cpu.c | 22 +++++++++++++++++----- > 1 file changed, 17 insertions(+), 5 deletions(-) > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > index 852ecccd8920..5e42c92a8456 100644 > --- a/arch/riscv/kernel/cpu.c > +++ b/arch/riscv/kernel/cpu.c > @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init); > .uprop = #UPROP, \ > .isa_ext_id = EXTID, \ > } > + > /* > * Here are the ordering rules of extension naming defined by RISC-V > * specification : > - * 1. All extensions should be separated from other multi-letter extensions > - * by an underscore. > + * > + * 1. All multi-letter extensions should be separated from other multi-letter > + * extensions by an underscore. > + * > * 2. The first letter following the 'Z' conventionally indicates the most > * closely related alphabetical extension category, IMAFDQLCBKJTPVH. > - * If multiple 'Z' extensions are named, they should be ordered first > - * by category, then alphabetically within a category. > + * 'Z' extensions should be sorted after single-letter extensions and before > + * any higher-privileged extensions. > + * If multiple 'Z' extensions are named, they should be ordered first by > + * category, then alphabetically within a category. > + * > * 3. Standard supervisor-level extensions (starts with 'S') should be > * listed after standard unprivileged extensions. If multiple > * supervisor-level extensions are listed, they should be ordered > * alphabetically. > - * 4. Non-standard extensions (starts with 'X') must be listed after all > + * > + * 4 Standard machine-level extensions (starts with 'Zxm') should be > + * listed after any lower-privileged, standard extensions. If multiple > + * machine-level extensions are listed, they should be ordered > + * alphabetically. > + * > + * 5. Non-standard extensions (starts with 'X') must be listed after all > * standard extensions. They must be separated from other multi-letter > * extensions by an underscore. > */ > -- > 2.38.1 > Alternatively, we could change the comment to just point out the spec chapter and provide an example, e.g. /* * The canonical order of ISA extension names in the ISA string is defined in * chapter 27 of the unprivileged spec. An example string following the * order is * * rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux * * Notice how Z-extensions are first sorted by category using the canonical * order of the first letter following the Z. Extension groups are in the * order specified in chapter 27. Extensions within each group are sorted * alphabetically. */ Thanks, drew
