On Tue, Nov 29, 2022 at 04:54:19PM +0000, Conor Dooley wrote: > On Tue, Nov 29, 2022 at 05:12:23PM +0100, Andrew Jones wrote: > > 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. > > IDK, maybe add the reference & the example but keep the summary? It risks needing to synchronize the comment with the spec. Also, the comment doesn't need to reproduce the flexible specifications, since Linux has a single implementation (it always puts an underscore between single-letter extensions and the first multi-letter extension, for example). So, rather than paraphrase too much of the spec, we could just point out Linux's specific implementation (with the help of an example). I don't feel that strongly about it though, so we can keep the text the spec paraphrasing too. Thanks, drew > > > /* > > * 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
