Getter/setter macros

[darsor]

Background

I'm interested in implementing support for fixedpoint fields (per SystemRDL/#188). Specifically, I'd like the ability to call a getter/setter on a field using floating-point values that are automatically translated to/from fixedpoint fields. This proposal is a step in that direction.

Current Access Options

There are currently two ways to get/set the value of a field:

1. Using bitfield structs
2. Doing manual memory accesses, bit shifts, and bit masks based on the width/position/mask defines

Proposal

I propose an additional method: Function-like getter/setter macros.

Example

Consider the following:

example.rdl

addrmap top {
    reg {
        field {
            sw=rw; hw=r;
        } f[8];
    } r1;
};

example.h

#include "reg_utils.h"

// Reg - top::r1
#define TOP__R1__F_bm 0xff
#define TOP__R1__F_bp 0
#define TOP__R1__F_bw 8
// vvv proposed macros below vvv
#define TOP__R1__F_get() get_reg32(&top.r1, 0, 0xff)
#define TOP__R1__F_set(value) set_reg32(&top.r1, 0, 0xff, value)
// ^^^ proposed macros above ^^^

// Addrmap - top
typedef struct __attribute__ ((__packed__)) {
    uint32_t r1;
} top_t;

// Instances
#define top (*(volatile top_t *)0x20000000UL)

reg_utils.h

uint32_t reg32_get(volatile uint32_t* reg, uint32_t pos, uint32_t mask) {
    return (*reg >> pos) & mask;
}

void reg32_set(volatile uint32_t* reg, uint32_t pos, uint32_t mask, uint32_t value) {
    uint32_t reg_value = *reg; // read
    reg_value &= ~(mask << pos); // clear
    reg_value |= (value & mask) << pos; // set
    *reg = reg_value; // write
}

Advantages

1. The getter/setter macros are much less verbose (and less error prone) than manual memory accesses using the width/position/mask defines.
2. The getter/setter macros don't deal with implementation-defined behavior like bitfields do.
3. The reg32_get/set functions can be overridden or supplied by the user to work with memories that can't be accessed directly (like a remote device).

Disadvantages:

1. As written above, the macros only work for a single instantiation (base address) of the addrmap.
   a. Shouldn't be a big issue since multiple instantiations of a regfile can be used in an addrmap with similar effect.
2. Need to include reg_utils.h in any files that use the macros.
3. Probably others that I can't think of right now.

Thoughts? Does this fit in the scope of this exporter?