printk格式中p的百分比[p]的含义

Question

问题是关于printk格式.我正在阅读的文档位于此处

以下是我要问的摘录:

Physical addresses types phys_addr_t:

    %pa[p]  0x01234567 or 0x0123456789abcdef

    For printing a phys_addr_t type (and its derivatives, such as
    resource_size_t) which can vary based on build options, regardless of
    the width of the CPU data path. Passed by reference.

是什么[p]在%pa[p]立场？这是什么意思？

Answer 1

将p在[p]代表phys_addr_t在使用时%pap.这是类似于d中%pad表示dma_addr_t,因为所引用的文献中看到:

DMA addresses types dma_addr_t:

    %pad    0x01234567 or 0x0123456789abcdef

    For printing a dma_addr_t type which can vary based on build options,
    regardless of the width of the CPU data path. Passed by reference.

由于它没有提供%pa和之间记录的差异%pap,这意味着它们的行为相同.括号内的内容表示可选修饰符.这可以在%*pE文档后面的定义中看到:

Raw buffer as an escaped string:

    %*pE[achnops]
...
    The conversion rules are applied according to an optional combination
    of flags (see string_escape_mem() kernel documentation for the
    details):
        a - ESCAPE_ANY
        c - ESCAPE_SPECIAL
        h - ESCAPE_HEX
        n - ESCAPE_NULL
        o - ESCAPE_OCTAL
        p - ESCAPE_NP
        s - ESCAPE_SPACE
    By default ESCAPE_ANY_NP is used.