如何在U-Boot和Linux内核中添加自定义ATAG变量？

Question

我想在U-Boot和Linux内核中添加自定义的atag变量。

我如何才能做到这一点？

是否有在U-Boot和Linux中添加ATAG变量的过程

Answer 1

请按照以下步骤操作：

为了实现这个目标，有两个部分需要修改。一个是U-Boot，另一个是Linux内核。

    1.    U-Boot changes required :

        A.     Make sure the  CONFIG_CMDLINE_TAG/CONFIG_SETUP_MEMORY_TAGS/CONFIG_INITRD_TAG are defined in you project definition header file ( u-boot/include/configs/am335x_evm.h ), and we  can add our own tag here, eg. CONFIG_CUSTOM_TAG.

        B.     Add the structure definition you wanna append w/ ATAG in u-boot/include/asm-arm/setup.h, eg.

            #define ATAG_CUSTOM 0x5441000a
            struct tag_custom{
            unsigned char mac_addr[6];
            };

        C.    Add the struct at the tail of "u"...

            struct tag {
                    struct tag_header hdr;
                    union {
                    struct tag_core         core;
                    struct tag_mem32        mem;
                    struct tag_videotext    videotext;
                    struct tag_ramdisk      ramdisk;
                    struct tag_initrd       initrd;
                    struct tag_serialnr     serialnr;
                    struct tag_revision     revision;
                    struct tag_videolfb     videolfb;
                    struct tag_cmdline      cmdline;

                    /*
                     * Acorn specific
                     */
                    struct tag_acorn        acorn;

                    /*
                     * DC21285 specific
                     */
                    struct tag_memclk       memclk;

                    /****** INFOTECH Custom TAG ********/

                   struct tag_custom custom;
                    } u;
                };

        D.    Add implementation code in lib_arm/bootm.c:

            static void setup_custom_tag(bd_t *bd);

            static void setup_custom_tag(bd_t *bd) {
                params->hdr.tag = ATAG_CUSTOM;
                   params->hdr.size = tag_size (tag_macaddr);
                params->u.custom.cmd =0;
                params = tag_next (params);
            }

        E.    Add "#ifdef CONFIG_CUSTOM_TAG / #endif" at every place you change the code.

        F.    Done of U-Boot modification.

2. Linux Changes required:

        A.    Add parse tag code in linux/arch/arm/kernel/setup.c:

            int cmd;
            static int __init parse_tag_custom(const struct tag *tag){
                    printk("u.custom.cmd=%d\n",tag->u.custom.cmd);
                return 0;
            }

            __tagtable(ATAG_MACADDR, parse_tag_custom);

        B. Add the structure declaration as U-Boot did in linux/include/asm-arm/setup.h:

            #define ATAG_MACADDR 0x5441000a
            struct tag_custom {
                int cmd;
            };

        C. Add the struct at the tail of "u"...

            struct tag {
                struct tag_header hdr;
               union {
                    struct tag_core         core;
                 struct tag_mem32        mem;
                struct tag_videotext    videotext;
                struct tag_ramdisk      ramdisk;
                struct tag_initrd       initrd;
                struct tag_serialnr     serialnr;
                struct tag_revision     revision;
                struct tag_videolfb     videolfb;
                struct tag_cmdline      cmdline;

                /*
                 * Acorn specific
                 */
                struct tag_acorn        acorn;

                /*
                 * DC21285 specific
                 */
                struct tag_memclk       memclk;

                /* Add Infotech custom tag */

                struct tag_custom      custom;
                } u;
            };

        D. Done w/ Kernel parts.

Answer 2

最新的Linux内核正试图通过设备树来淘汰ATAGS。但是，setup.h文件定义了不同的ATAG值和结构。要解析它们，您需要添加类似以下内容的内容：

static int __init parse_tag_custom(const struct tag *tag)
{
    if (tag->hdr.size > CUSTOM_SIZE) {
         /* Use, storing or acting on passed values */ 
         tag->u.custom;
    }
    return 0;
}

__tagtable(ATAG_CUSTOM, parse_tag_custom);

在atags_parse.c中可以找到。当然，您需要将这些值添加到setup.h中的值。

u-boot可能定义较少，因为在大多数情况下，它通过内核命令行传递参数，因为这不是ARM特定的。命令参数或设备树可能是首选方法。如果你举一个例子说明你需要什么类型的配置，别人可能会给你更好的指导。

Answer 3

需要更改

1. U-Boot：

确保在你的项目定义头文件(u- CONFIG_CMDLINE_TAG/CONFIG_SETUP_MEMORY_TAGS/CONFIG_INITRD_TAG /include/configs/AM335xevm.h )中定义了引导，我们可以在这里添加我们自己的标签，例如。CONFIG_CUSTOM_TAG。B.在u-boot/include/asm-arm/setup.h中添加要附加w/ ATAG的结构定义，例如。#define ATAG_CUSTOM 0x5441000a结构tag_custom{ unsigned char mac_addr6；}；C.在“u”的尾部添加结构...结构标签{结构tag_header hdr；联合{结构tag_core核心；结构tag_mem32内存；结构tag_videotext视频文本；结构tag_ramdisk内存磁盘；结构tag_initrd初始化；结构tag_serialnr序列号；结构tag_revision修订版；struct tag_videolfb videolfb；struct tag_cmdline cmdline；/* * Acorn */ struct tag_acorn acorn；/* * DC21285 specific */ struct tag_memclk memclk；/****** INFOTECH自定义标签*/ struct tag_custom自定义；} u；}；D.在lib_arm/bootm.c中添加实现代码: static void setup_custom_tag(bd_t *bd)；static void setup_custom_tag(bd_t *bd) { params->hdr.tag = ATAG_CUSTOM；params->hdr.size = tag_size (tag_macaddr)；params->u.custom.cmd =0；params = tag_next (params)；} E.在您更改代码的每个位置添加"#ifdef CONFIG_CUSTOM_TAG / #endif“。F.完成U-Boot修改。

1. Linux Changes required:

A.在linux/arch/arm/kernel/setup.c中添加解析标签代码：

int cmd；static int __init parse_tag_custom(const struct tag *tag){ printk("u.custom.cmd=%d\n"，tag->u.custom.cmd)；return 0；} __tagtable(ATAG_MACADDR，parse_tag_custom)；

B.添加结构声明，如U-Boot在linux/include/asm-arm/setup.h中所做的那样：

#定义ATAG_MACADDR 0x5441000a结构tag_custom { int cmd；}；

C.在“u”的尾部添加结构...

结构标签{结构tag_header hdr；联合{结构tag_core核心；结构tag_mem32内存；结构tag_videotext视频文本；结构tag_ramdisk内存磁盘；结构tag_initrd初始化磁盘；结构tag_serialnr序列号；结构tag_revision修订版；结构tag_videolfb视频mem；结构tag_cmdline命令行；/* *橡子专用*/结构tag_acorn acorn；/* * DC21285专用*/结构tag_memclk memclk；/*添加Infotech自定义标签*/结构tag_custom自定义；} u；}；

D.使用内核部件完成。

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