#include <linux/bits.h>
#include <linux/bitfield.h>
#include <stdio.h>
#include <stdlib.h>
#include <perf/cpumap.h>
#include <api/fs/fs.h>
#include <errno.h>
#include "debug.h"
#include "header.h"

#define MIDR "/regs/identification/midr_el1"
#define MIDR_SIZE 19
#define MIDR_REVISION_MASK      GENMASK(3, 0)
#define MIDR_VARIANT_MASK       GENMASK(23, 20)

static int _get_cpuid(char *buf, size_t sz, struct perf_cpu cpu)
{
        char path[PATH_MAX];
        FILE *file;
        const char *sysfs = sysfs__mountpoint();

        assert(cpu.cpu != -1);
        if (!sysfs || sz < MIDR_SIZE)
                return EINVAL;

        scnprintf(path, PATH_MAX, "%s/devices/system/cpu/cpu%d" MIDR, sysfs, cpu.cpu);

        file = fopen(path, "r");
        if (!file) {
                pr_debug("fopen failed for file %s\n", path);
                return EINVAL;
        }

        if (!fgets(buf, MIDR_SIZE, file)) {
                pr_debug("Failed to read file %s\n", path);
                fclose(file);
                return EINVAL;
        }
        fclose(file);
        return 0;
}

int get_cpuid(char *buf, size_t sz, struct perf_cpu cpu)
{
        struct perf_cpu_map *cpus;
        int idx;

        if (cpu.cpu != -1)
                return _get_cpuid(buf, sz, cpu);

        cpus = perf_cpu_map__new_online_cpus();
        if (!cpus)
                return EINVAL;

        perf_cpu_map__for_each_cpu(cpu, idx, cpus) {
                int ret = _get_cpuid(buf, sz, cpu);

                if (ret == 0)
                        return 0;
        }
        return EINVAL;
}

char *get_cpuid_str(struct perf_cpu cpu)
{
        char *buf = malloc(MIDR_SIZE);
        int res;

        if (!buf)
                return NULL;

        /* read midr from list of cpus mapped to this pmu */
        res = get_cpuid(buf, MIDR_SIZE, cpu);
        if (res) {
                pr_err("failed to get cpuid string for CPU %d\n", cpu.cpu);
                free(buf);
                buf = NULL;
        }

        return buf;
}

/*
 * Return 0 if idstr is a higher or equal to version of the same part as
 * mapcpuid. Therefore, if mapcpuid has 0 for revision and variant then any
 * version of idstr will match as long as it's the same CPU type.
 *
 * Return 1 if the CPU type is different or the version of idstr is lower.
 */
int strcmp_cpuid_str(const char *mapcpuid, const char *idstr)
{
        u64 map_id = strtoull(mapcpuid, NULL, 16);
        char map_id_variant = FIELD_GET(MIDR_VARIANT_MASK, map_id);
        char map_id_revision = FIELD_GET(MIDR_REVISION_MASK, map_id);
        u64 id = strtoull(idstr, NULL, 16);
        char id_variant = FIELD_GET(MIDR_VARIANT_MASK, id);
        char id_revision = FIELD_GET(MIDR_REVISION_MASK, id);
        u64 id_fields = ~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK);

        /* Compare without version first */
        if ((map_id & id_fields) != (id & id_fields))
                return 1;

        /*
         * ID matches, now compare version.
         *
         * Arm revisions (like r0p0) are compared here like two digit semver
         * values eg. 1.3 < 2.0 < 2.1 < 2.2.
         *
         *  r = high value = 'Variant' field in MIDR
         *  p = low value  = 'Revision' field in MIDR
         *
         */
        if (id_variant > map_id_variant)
                return 0;

        if (id_variant == map_id_variant && id_revision >= map_id_revision)
                return 0;

        /*
         * variant is less than mapfile variant or variants are the same but
         * the revision doesn't match. Return no match.
         */
        return 1;
}