如何将uboot里面的参数传给recovery或kernel

原文地址：http://blog.csdn.net/dwyane_zhang/article/details/8441854

最近我们在做一个LCM两屏或三屏兼容的问题,所以首先要在uboot里面读出各屏的id,然后再将读得到的id传给recovery和kernel,实现机器的正常显示.

一.首先实现uboot读lcm的id.

          1.bootable/bootloader/lk/target/msm7627a_sku3_Q6_D/rules.mk是uboot里面宏开关,打开所显示的屏宏

DEFINES += DISPLAY_MIPI_CMD_PANEL_ILI9487=1DEFINES += DISPLAY_MIPI_CMD_PANEL_HX8357=1

 

          2.去初始化mipi的地方先读id. bootable/bootloader/lk/platform/msm_shared/mipi_dsi.c

              在函数int mipi_dsi_panel_initialize(struct mipi_dsi_panel_config *pinfo){       ......#if defined(DISPLAY_MIPI_CMD_PANEL_ILI9487)||defined(DISPLAY_MIPI_CMD_PANEL_HX8357)    mipi_dsi_cmd_bta_sw_trigger();    dat = mipi_viroyal_manufacture_id();    if(dat == 0x90)    {        lcm_flag = 8357;        //hx8357-c    }    else    {        lcm_flag = 9487;        //ili9487    }        pinfo_tmp =get_panel_info();    memcpy(pinfo, pinfo_tmp, sizeof(struct mipi_dsi_panel_config));#endif       ......}

 

           3.读到id后再初始化屏

                struct mipi_dsi_panel_config *get_panel_info(void){              .........#elif (DISPLAY_MIPI_CMD_PANEL_ILI9487)||(DISPLAY_MIPI_CMD_PANEL_HX8357)    if (lcm_flag == 8357)        return &hx8357_cmd_panel_info;    else        return &ili9487_cmd_panel_info;#endif               ..........}

 

这样在uboot里面就成功可以显示图片了,下面是如何将lcm_flag的值传给kernel了.

二.传lcm_flag给kernel

     1.uboot里面要做的bootable/bootloader/lk/app/aboot/aboot.c

         其实原生态的android系统就有一个将uboot传给kernel的例子,那就是跟踪代码static const char *boot_splash = " splash=1";

          我做的也是效仿系统做的,先定义一个字符串

static const char *lcm_flg_ili9486 = " lcmflag=9486";static const char *lcm_flg_nt35310 = " lcmflag=5310";

 

然后在下面的函数copy到kernel

void boot_linux(void *kernel, unsigned *tags,        const char *cmdline, unsigned machtype,        void *ramdisk, unsigned ramdisk_size){   .....        if(!boot_into_recovery)    {        cmdline_len += strlen(boot_splash);        #if DISPLAY_TYPE_MIPI        if (lcm_flag == 8357)        cmdline_len += strlen(lcm_flg_hx8357c);        else         cmdline_len += strlen(lcm_flg_ili9487);        #endif   .....       if (!boot_into_recovery)        {        #if DISPLAY_TYPE_MIPI            if (lcm_flag == 8357)               src = lcm_flg_hx8357c;            else               src = lcm_flg_ili9487;        #endif        if (have_cmdline) --dst;        while ((*dst++ = *src++));       .....}

 

这样uboot里面的动作就做完了,即是将uboot里面的数据copy到一个数组里面,这个数组能从uboot传给kernel.

三.kernel接受uboot传来的字符串

msm7627a/kernel/arch/arm/mach-msm/board-msm7x27a.c

 

在这个函数里面接受(依据自己用的平台阿,要灵活),同样是模仿boot_splash,在代码里添加接受字符串,并转化为数字

/* LK lcm_flag, 0 - off, 1 - on */int lcm_flag = 0;static int __init lk_lcmflag_setup(char *str){    lcm_flag = simple_strtol(str, NULL, 0);    printk("lcmflag = %d\n", lcm_flag);    return 1;}__setup("lcmflag=", lk_lcmflag_setup);

 

这样就算是取到lcm_flag的值了,然后在具体的驱动中extern int lcm_flag即可,简单吧.其实技术就那样,很怕人认真,呵呵.开玩笑的.