On Thu, Dec 01, 2022 at 09:27:43AM +0100, Andrew Jones wrote: > On Wed, Nov 30, 2022 at 11:41:24PM +0000, Conor Dooley wrote: > > From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> > > > > While the current list of rules may have been accurate when created > > it now lacks some clarity in the face of isa-manual updates. Instead of > > trying to continuously align this rule-set with the one in the > > specifications, change the role of this comment. > > > > This particular comment is important, as the array it "decorates" > > defines the order in which the ISA string appears to userspace in > > /proc/cpuinfo. > > > > Re-jig and strengthen the wording to provide contributors with a set > > order in which to add entries & note why this particular struct needs > > more attention than others. > > > > While in the area, add some whitespace and tweak some wording for > > readability's sake. > > > > Suggested-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx> > > Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> > > --- > > arch/riscv/kernel/cpu.c | 49 ++++++++++++++++++++++++++++++----------- > > 1 file changed, 36 insertions(+), 13 deletions(-) > > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > > index 852ecccd8920..68b2bd0cc3bc 100644 > > --- a/arch/riscv/kernel/cpu.c > > +++ b/arch/riscv/kernel/cpu.c > > @@ -120,22 +120,45 @@ 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. > > - * 2. The first letter following the 'Z' conventionally indicates the most > > + * The canonical order of ISA extension names in the ISA string is defined in > > + * chapter 27 of the unprivileged specification. > > + * > > + * Ordinarily, for in-kernel data structures, this order is unimportant but > > + * isa_ext_arr defines the order of the ISA string in /proc/cpuinfo. > > + * > > + * The specification uses vague wording, such as should, when it comes to > > + * ordering so for our purposes the following rules apply: > > + * > > + * 1. All multi-letter extensions must be separated from other multi-letter > > 1. All multi-letter extensions must be separated from other extensions by an > underscore. > > (Because we always lead multi-letter extensions with underscore, even the > first one, which follows the single-letter extensions.) Yah, I need to think as if I am using De Morgan's... The DT ABI requires "should" and permits this. The uAPI is "must"/"will" and always has an _. I'll propagate that change to the docs patch too. > > + * extensions by an underscore. > > + * > > + * 2. Additional standard extensions (starting with 'Z') must be sorted after > > + * single-letter extensions and before any higher-privileged extensions. > > + > > + * 3. 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. > > - * 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 > > + * If multiple 'Z' extensions are named, they should be ordered first by > > + * category, then alphabetically within a category. > > + * > > + * 3. Standard supervisor-level extensions (starting with 'S') must be listed > > + * after standard unprivileged extensions. If multiple > > + * supervisor-level extensions are listed, they must be ordered > > * alphabetically. > > - * 4. 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. > > + * > > + * 4. Standard machine-level extensions (starting with 'Zxm') must be listed > > + * after any lower-privileged, standard extensions. If multiple > > + * machine-level extensions are listed, they must be ordered > > + * alphabetically. > > + * > > + * 5. Non-standard extensions (starts with 'X') must be listed after all > > + * standard extensions. > ^and alphabetically. "If multiple non-standard extensions are listed, they must be ordered alphabetically." I'll also propagate this to the doc one, if I have not already. > Otherwise, > > Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx> Cool. I'll give it a bit before respinning, but I think we are at least getting less ambiguous as time goes on.. Thanks, Conor.
