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Re: [PATCH v3 3/4] dt-bindings: riscv: add new riscv, isa strings for em
Re: [PATCH v3 3/4] dt-bindings: riscv: add new riscv, isa strings for emulators
Thu, 18 Aug 2022 06:24:17 +0000
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0
On 18/08/2022 06:48, Andrew Jones wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
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> On Thu, Aug 18, 2022 at 07:40:14AM +0200, Andrew Jones wrote:
>> On Wed, Aug 17, 2022 at 09:12:12PM +0100, Conor Dooley wrote:
>>> From: Conor Dooley <email@example.com>
>>> The QEMU virt and spike machines currently export a riscv,isa string of
>>> While the RISC-V foundation has been ratifying a bunch of extenstions
>>> etc, the kernel has remained relatively static with what hardware is
>>> supported - but the same is not true of QEMU. Using the virt machine
>>> and running dt-validate on the dumped dtb fails, partly due to the
>>> unexpected isa string.
>>> Rather than enumerate the many many possbilities, change the pattern
>>> to a regex, with the following assumptions:
>>> - the single letter order is fixed & we don't care about things that
>>> can't even do "ima"
>>> - the standard multi letter extensions are all in a "_z<foo>" format
>>> where the first letter of <foo> is a valid single letter extension
>>> - _s & _h are used for supervisor and hyper visor extensions.
>>> - after the first two chars, a standard multi letter extension name
>>> could be an english word (ifencei anyone?) so it's not worth
>>> restricting the charset
>>> - vendor ISA extensions begind with _x and have no charset restrictions
>>> - we don't care about an e extension from an OS pov
>>> - that attempting to validate the contents of the multiletter extensions
>>> with dt-validate beyond the formatting is a futile, massively verbose
>>> or unwieldy exercise at best.
>>> - ima are required
>>> The following limitations also apply:
>>> - multi letter extension ordering is not enforced. dt-schema does not
>>> appear to allow for named match groups, so the resulting regex would
>>> be even more of a headache.
>>> - ditto for the numbered extensions.
>>> Finally, add me as a maintainer of the binding so that when it breaks
>>> in the future, I can be held responsible!
>>> Reported-by: Rob Herring <firstname.lastname@example.org>
>>> Signed-off-by: Conor Dooley <email@example.com>
>>> Palmer, feel free to drop the maintainer addition. I just mostly want
>>> to clean up my own mess on this when they decide to ratify more
>>> extensions & this comes back up again.
>>> Documentation/devicetree/bindings/riscv/cpus.yaml | 5 ++---
>>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml
>>> index 873dd12f6e89..c0e0bc5dce04 100644
>>> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
>>> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
>>> @@ -9,6 +9,7 @@ title: RISC-V bindings for 'cpus' DT nodes
>>> - Paul Walmsley <firstname.lastname@example.org>
>>> - Palmer Dabbelt <email@example.com>
>>> + - Conor Dooley <firstname.lastname@example.org>
>>> description: |
>>> This document uses some terminology common to the RISC-V community
>>> @@ -79,9 +80,7 @@ properties:
>>> insensitive, letters in the riscv,isa string must be all
>>> lowercase to simplify parsing.
>>> $ref: "/schemas/types.yaml#/definitions/string"
>>> - enum:
>>> - - rv64imac
>>> - - rv64imafdc
>>> + pattern:
> Actually we don't want S and H extensions to be treated like Z, but rather
> like X. Only Z extensions have the category character convention. (And I'm
> still tempted to just drop the enforcement from Z too, since it adds
> additional maintenance and we've already settled for something less than
Yeah, I think you are probably right there. I'll let this one sit for
a few days & if nothing else comes in I'll send a v4 with the charset
>>> # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>>> timebase-frequency: false
>> Reviewed-by: Andrew Jones <email@example.com>