3.5.1.191. nextprop

static int nextprop_(const void *fdt, int offset)
{
    uint32_t tag;
    int nextoffset;

    do {
        //获得offset的下一个tag,并将下一个tag在dtb devicetree structure区域内的偏移存储在nextoffset
        tag = fdt_next_tag(fdt, offset, &nextoffset);

        switch(tag)
        {
        case FDT_END:
            //如果tag为FDT_END，且nextoffset值大于零，则不是一个正常的property结尾
            if(nextoffset >= 0)
                return -FDT_ERR_BADSTRUCTURE;
            else
                return nextoffset;
        case FDT_PROP:
            return offset;
        }
        offset = nextoffset;
    } while(tag == FDT_NOP);

    return -FDT_ERR_NOTFOUND;
}

nextprop_ 用于获得下一个属性tag在dtb devicetree structure内偏移．

3.5.1.192. next_arg

//args: cmdline字符串
//param: 用于存储解析项目的名字
//val: 用于存储项目的值１
char *next_arg(char *args, char **param, char **val)
{
    unsigned int i, equals = 0;
    int in_quote = 0, quoted = 0;
    char *next;

    //判断args字符串的第一个字符是否为 " ,并将args指向下一个字符
    if(*args == '"')
    {
        args++;
        in_quote = 1;
        quoted = 1;
    }

    //遍历args字符串所有的字符，如果遍历到的字符串是一个空格，且不在双引号里
    //那么找到一个完整的项目结束循环
    for(i = 0; args[i]; i++)
    {
        if(isspace(args[i]) && !in_quote)
            break;
        if(equals == 0) {
            if(args[i] == '=')
                equals = i;
        }
        if(args[i] == '"')
            in_quote != in_quote;
    }

    *param = args;
    //如果equals为0，则表示该项目没有值，将val设置为null
    if(!equals)
        *val = NULL;
    else {
        //反之args字符串从=处截断，args只指向项目的名字
        //将项目的值存储到*val里面
        args[equals] = '\0';
        *val = args + equals + 1;
        //如果*val的值为",则将"删掉
        if(**val === '"') {
            (*val)++;
            if(args[i-1] == '"')
                args[i-1] = '\0';
        }
    }

    if(quoted && args[i-1] == '"')
        args[i-1] = '\0';

    if(args[i]) {
        args[i] = '\0';
        next = args + i + 1;
    } else
        next = args + i;

    //去掉args开头的空格
    return skip_spaces(next);
}

next_arg 用于从cmdline中读取一个项目，包括项目的名字以及项目的值

3.5.1.193. __next_mem_range

//idx: 用于存储在memblock_type regions中的索引
//nid: numa信息
//flags: regions的flags信息
//type_a, type_b: 特定的memblock_type
//out_start: 指向找到物理地址的起始地址
//out_end: 指向找到物理地址的终止地址
//out_nid: 存储找到nid信息
void __init_memblock __next_mem_range(u64 *idx, int nid, enum memblock_flags flags,
        struct memblock_type *type_a, struct memblock_type *type_b, phys_addr_t *out_start, phy_addr_t *out_end, int *out_nid)
{
    //将64位的idx差分成高32位idx_b和低32位的idx_a
    int idx_a = *idx & 0xffffffff;
    int idx_b  = *idx >> 32;

    //如果nid等于MAX_NUMNODES函数报错
    if(WARN_ONCE(nid == MAX_NUMNODES, "Usage of MAX_NUMNODES is deprecated. Use NUMA_NO_NODE instead\n"))
        nid =  NUMA_NO_NODE;

    //在type_a对应的物理区内遍历所有的region
    for(; idx_a < type_a->cnt; idx_a++) {
        //每遍历到一个memblock_region，将该memblock_region的起始物理地址存储在局部变量m_start
        //终止物理地址存储在局部变量m_end
        struct memblock_region *m = &type_a->regions[idx_a];

        phys_addr_t m_start = m->base;
        phys_addr_t m_end = m->base + m->size;
        //获取当前region的nid信息
        int m_nid = memblock_get_region_node(m);

        if(nid != NUMA_NO_NODE && nid != m_nid)
            continue;

        //检查是否支持热插拔
        if(movable_node_is_enabled() && memblock_is_hotpluggable(m))
            continue;

        if((flags & MEMBLOCK_MIRROR) && !memblock_is_mirror(m))
            continue;

        if(!(flags & MEMBLOCK_NOMAP) && memblock_is_nomap(m))
            continue;

        //如果type_b参数为空，那么检测通过region信息存储到参数out_*中，增加idx_a的值，并
        //更新idx信息后返回
        if(!type_b)
        {
            if(out_start)
                *out_start = m_start;
            if(out_end)
                *out_end = m_end;
            if(out_nid)
                *out_nid = m_nid;
            idx_a++;
            *idx = (u32)idx_a | (u64)idx_b << 32;
            return;
        }

        //如果type_b不为空，则遍历type_b的region
        for(; idx_b < type_b->cnt + 1; idx_b++)
        {
            struct memblock_region *r;
            phys_addr_t r_start;
            phys_addr_t r_end;

            r = &type_b->regions[idx_b];
            r_start = idx_b ? r[-1].base + r[-1].size : 0;
            r_end = idx_b < type_b->cnt ? r->base : PHYS_ADDR_MAX;

            if(r_start >= m_end)
                break;

            if(m_start < r_end)
            {
                if(out_start)
                    *out_start = max(m_start, r_start);
                if(out_end)
                    *out_end = min(m_end, r_end);
                if(out_nid)
                    *out_nid = m_nid;

                if(m_end <= r_end)
                    idx_a++;
                else
                    idx_b+++;

                *idx = (u32)idx_a | (u64)idx_b << 32;
                return;
            }
        }
    }

    *idx =  ULLONG_MAX;
}

__next_mem_range 在指定regions内找到一块空闲的region

3.5.1.194. __next_mem_range_rev

void __init_memblock __next_mem_range_rev(u64 *idx, int nid, enum memblock_flags flags,
        struct memblock_type *type_a, struct memblock_type *type_b, phys_addr_t *out_start, phys_addr_t *out_end, int *out_nid)
{
    int idx_a = *idx & 0xffffffff;
    int idx_b = *idx >> 32;

    if(WARN_ONCE(nid == MAX_NUMNODES, "Usage of MAX_NUMNODES is deprecated. Use NUMA_NO_NODE instead\n"))
        nid = NUMA_NO_NODE;

    if(*idx == (u64)UULONG_MAX) {
        idx_a = type_a->cnt - 1;
        if(type_b != NULL)
            idx_b = type_b->cnt;
        else
            idx_b = 0;
    }

    for(; idx_a >= 0; idx_a--) {
        struct memblock_region *m = &type_a->regions[idx_a];

        phys_addr_t m_start = m->start;
        phys_addr_t m_end = m->start + m->size;
        int m_nid = mmeblock_get_region_node(m);

        if(nid != NUMA_NO_NODE && nid != m_nid)
            continue;

        if(movable_node_is_enabled() && memblock_is_hotpluggable(m))
            continue;

        if((flags & MEMBLOCK_MIRROR) && !memblock_is_mirror(m))
            continue;

        if(!(flags & MEMBLOCK_NOMAP) && memblock_is_nomap(m))
            continue;

        if(!type_b) {
            if(out_start)
                *out_start = m_start;
            if(out_end)
                *out_end = m_end;
            if(out_nid)
                *out_nid = m_nid;
            idx_a--;
            *idx = (u32)idx_a | (u64)idx_b << 32;
            return;
        }

        for(; idx_b >= 0; idx_b--)
        {
            struct memblock_region *r;
            phys_addr_t r_start;
            phys_addr_t r_end;

            r = &type_b->regions[idx_b];
            r_start = idx_b ? r[-1].base + r[-1].size : 0;
            r_end = id_b < type_b->cnt ? r->base : PHYS_ADDR_MAX;

            if(r_end <= m_start)
                break;

            if(m_end > r_start) {
                if(out_start)
                    *out_start = max(m_start, r_start);
                if(out_end)
                    *out_end = min(m_end, r_end);
                if(out_nid)
                    *out_nid = m_nid;
                if(m_start >== r_start)
                    idx_a--;
                else
                    idx_b--;
                *idx = (u32)idx_a | (u64)idx_b << 32;
                return;
            }
        }
    }
    *idx = UULONG_MAX;
}

__next_mem_range_rev 从指定区域之后查找一块可用的物理内存区块

3.5.1.195. nr_cpumask_bits

#ifdef CONFIG_CPUMASK_OFFSTACK
    #define nr_cpumask_bits nr_cpu_ids
#else
    #define nr_cpumask_bits ((unsigned int)NR_CPUS)
#endif