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linux-next/Documentation/devicetree
Conor Dooley 299824e68b
dt-bindings: riscv: add new riscv,isa strings for emulators
The QEMU virt and spike machines currently export a riscv,isa string of
"rv64imafdcsuh",

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:
- ima are required
- 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
- convention says that 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
- as the above is just convention, don't apply any charset restrictions
  to reduce future churn
- 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

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 <robh@kernel.org>
Link: https://lore.kernel.org/linux-riscv/20220803170552.GA2250266-robh@kernel.org/
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220823183319.3314940-4-mail@conchuod.ie
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
2022-10-12 17:05:17 -07:00
..
bindings dt-bindings: riscv: add new riscv,isa strings for emulators 2022-10-12 17:05:17 -07:00
changesets.rst
dynamic-resolution-notes.rst
index.rst
kernel-api.rst
of_unittest.rst of: unittest: add program to process EXPECT messages 2022-02-28 15:20:32 -06:00
overlay-notes.rst of: overlay: rework overlay apply and remove kfree()s 2022-04-25 10:56:11 -05:00
usage-model.rst