Re: [RFC PATCH v7 05/18] scripts: Introduce scripts/aarch64_sysreg_helpers module

> On 26 Jul 2026, at 8:59 PM, Eric Auger <[email protected]> wrote:
> 
> !-------------------------------------------------------------------|
>  CAUTION: External Email
> 
> |-------------------------------------------------------------------!
> 
> We plan to reuse get_opcode() and extract_idregs_from_registers_json()
> functions in another script. So let's move them into a module
> 
> No functional change intended.
> 
> Signed-off-by: Eric Auger <[email protected]>
> ---
> scripts/aarch64_sysreg_helpers.py            | 109 +++++++++++++++++++
> scripts/update-aarch64-cpu-sysregs-header.py |  85 +--------------
> 2 files changed, 110 insertions(+), 84 deletions(-)
> create mode 100644 scripts/aarch64_sysreg_helpers.py
> 
> diff --git a/scripts/aarch64_sysreg_helpers.py b/scripts/aarch64_sysreg_helpers.py
> new file mode 100644
> index 0000000000..dd5ec4bafa
> --- /dev/null
> +++ b/scripts/aarch64_sysreg_helpers.py
> @@ -0,0 +1,109 @@
> +#!/usr/bin/env python3
> +
> +# Helpers used in aarch64 sysreg definition generation
> +#
> +# Copyright (C) 2026 Red Hat, Inc.
> +#
> +# Authors: Eric Auger <[email protected]>
> +#
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +
> +import json
> +import os
> +
> +# Some regs have op code values like 000x, 001x. Anyway we don't need
> +# them. Besides some regs are undesired in the generated file such as
> +# VMPIDR_EL2 and VPIDR_EL2 which are outside of the IDreg scope we
> +# are interested in and are tricky to decode as their system accessor
> +# refer to MPIDR_EL1/MIDR_EL1 respectively
> +
> +skiplist = ['ALLINT', 'PM', 'S1_', 'S3_', 'SVCR', \
> +            'VMPIDR_EL2', 'VPIDR_EL2']
> +
> +# returns the int value of a given @opcode for a reg @encoding
> +def get_opcode(encoding, opcode):
> +    fvalue = encoding.get(opcode)
> +    if fvalue:
> +        value = fvalue.get('value')
> +        if isinstance(value, str):
> +            value = value.strip("'")
> +            value = int(value, 2)
> +            return value
> +    return -1
> +
> +def extract_idregs_from_registers_json(filename):
> +    """
> +    Load a Registers.json file and extract all ID registers, decode their
> +    opcode and dump the information in target/arm/cpu-sysregs.h.inc
> +
> +    Args:
> +        filename (str): The path to the Registers.json
> +    returns:
> +        idregs: list of ID regs and their encoding
> +    """
> +    if not os.path.exists(filename):
> +        print(f"Error: {filename} could not be found!")
> +        return {}
> +
> +    try:
> +        with open(filename, 'r') as f:
> +            register_data = json.load(f)
> +
> +    except json.JSONDecodeError:
> +        print(f"Could not decode json from '{filename}'!")
> +        return {}
> +    except Exception as e:
> +        print(f"Unexpected error while reading {filename}: {e}")
> +        return {}
> +
> +    registers = [r for r in register_data if isinstance(r, dict) and \
> +                r.get('_type') == 'Register']
> +
> +    idregs = {}
> +
> +    # Some regs have op code values like 000x, 001x. Anyway we don't need
> +    # them. Besides some regs are undesired in the generated file such as
> +    # VMPIDR_EL2 and VPIDR_EL2 which are outside of the IDreg scope we
> +    # are interested in and are tricky to decode as their system accessor
> +    # refer to MPIDR_EL1/MIDR_EL1 respectively
> +
> +    skiplist = ['ALLINT', 'PM', 'S1_', 'S3_', 'SVCR', \
> +                'VMPIDR_EL2', 'VPIDR_EL2']
> +
> +    for register in registers:
> +        reg_name = register.get('name')
> +
> +        is_skipped = any(term in (reg_name or "").upper() for term in skiplist)
> +
> +        if reg_name and not is_skipped:
> +            accessors = register.get('accessors', [])
> +
> +            for accessor in accessors:
> +                type = accessor.get('_type')
> +                if type in ['Accessors.SystemAccessor']:
> +                    encoding_list = accessor.get('encoding')
> +
> +                    if isinstance(encoding_list, list) and encoding_list and \
> +                       isinstance(encoding_list[0], dict):
> +                        encoding_wrapper = encoding_list[0]
> +                        encoding_source = encoding_wrapper.get('encodings', \
> +                                                               encoding_wrapper)
> +
> +                        if isinstance(encoding_source, dict):
> +                                op0 = get_opcode(encoding_source, 'op0')
> +                                op1 = get_opcode(encoding_source, 'op1')
> +                                op2 = get_opcode(encoding_source, 'op2')
> +                                crn = get_opcode(encoding_source, 'CRn')
> +                                crm = get_opcode(encoding_source, 'CRm')
> +                                encoding_str=f"{op0} {op1} {crn} {crm} {op2}"
> +
> +                # ID regs are assumed within this scope
> +                if op0 == 3 and (op1 == 0 or op1 == 1 or op1 == 3) and \
> +                   crn == 0 and (crm >= 0 and crm <= 7) and (op2 >= 0 and op2 <= 7):
> +                    idregs[reg_name] = encoding_str
> +
> +    return idregs
> +
> +
> +
> diff --git a/scripts/update-aarch64-cpu-sysregs-header.py b/scripts/update-aarch64-cpu-sysregs-header.py
> index 8c337147dd..43107264e9 100755
> --- a/scripts/update-aarch64-cpu-sysregs-header.py
> +++ b/scripts/update-aarch64-cpu-sysregs-header.py
> @@ -17,90 +17,7 @@
> import json
> import os
> import sys
> -
> -# Some regs have op code values like 000x, 001x. Anyway we don't need
> -# them. Besides some regs are undesired in the generated file such as
> -# VMPIDR_EL2 and VPIDR_EL2 which are outside of the IDreg scope we
> -# are interested in and are tricky to decode as their system accessor
> -# refer to MPIDR_EL1/MIDR_EL1 respectively
> -
> -skiplist = ['ALLINT', 'PM', 'S1_', 'S3_', 'SVCR', \
> -            'VMPIDR_EL2', 'VPIDR_EL2']
> -
> -# returns the int value of a given @opcode for a reg @encoding
> -def get_opcode(encoding, opcode):
> -    fvalue = encoding.get(opcode)
> -    if fvalue:
> -        value = fvalue.get('value')
> -        if isinstance(value, str):
> -            value = value.strip("'")
> -            value = int(value, 2)
> -            return value
> -    return -1
> -
> -def extract_idregs_from_registers_json(filename):
> -    """
> -    Load a Registers.json file and extract all ID registers, decode their
> -    opcode and dump the information in target/arm/cpu-sysregs.h.inc
> -
> -    Args:
> -        filename (str): The path to the Registers.json
> -    returns:
> -        idregs: list of ID regs and their encoding
> -    """
> -    if not os.path.exists(filename):
> -        print(f"Error: {filename} could not be found!")
> -        return {}
> -
> -    try:
> -        with open(filename, 'r') as f:
> -            register_data = json.load(f)
> -
> -    except json.JSONDecodeError:
> -        print(f"Could not decode json from '{filename}'!")
> -        return {}
> -    except Exception as e:
> -        print(f"Unexpected error while reading {filename}: {e}")
> -        return {}
> -
> -    registers = [r for r in register_data if isinstance(r, dict) and \
> -                r.get('_type') == 'Register']
> -
> -    idregs = {}
> -
> -    for register in registers:
> -        reg_name = register.get('name')
> -
> -        is_skipped = any(term in (reg_name or "").upper() for term in skiplist)
> -
> -        if reg_name and not is_skipped:
> -            accessors = register.get('accessors', [])
> -
> -            for accessor in accessors:
> -                type = accessor.get('_type')
> -                if type in ['Accessors.SystemAccessor']:
> -                    encoding_list = accessor.get('encoding')
> -
> -                    if isinstance(encoding_list, list) and encoding_list and \
> -                       isinstance(encoding_list[0], dict):
> -                        encoding_wrapper = encoding_list[0]
> -                        encoding_source = encoding_wrapper.get('encodings', \
> -                                                               encoding_wrapper)
> -
> -                        if isinstance(encoding_source, dict):
> -                                op0 = get_opcode(encoding_source, 'op0')
> -                                op1 = get_opcode(encoding_source, 'op1')
> -                                op2 = get_opcode(encoding_source, 'op2')
> -                                crn = get_opcode(encoding_source, 'CRn')
> -                                crm = get_opcode(encoding_source, 'CRm')
> -                                encoding_str=f"{op0} {op1} {crn} {crm} {op2}"
> -
> -                # ID regs are assumed within this scope
> -                if op0 == 3 and (op1 == 0 or op1 == 1 or op1 == 3) and \
> -                   crn == 0 and (crm >= 0 and crm <= 7) and (op2 >= 0 and op2 <= 7):
> -                    idregs[reg_name] = encoding_str
> -
> -    return idregs
> +from aarch64_sysreg_helpers import extract_idregs_from_registers_json
> 
> if __name__ == "__main__":
>     # Single arg expected: the path to the Registers.json file
> -- 
> 2.53.0
> 

Reviewed-by: Khushit Shah <[email protected]>