需要在各層如：bootloader、kernel、framework、system-app獲取uboot的Env需要如下步驟
以905平臺(tái)設(shè)置控制臺(tái)日志等級(jí)為例

1. 將Env環(huán)境變量預(yù)置并且作為bootargs(傳遞給內(nèi)核的啟動(dòng)參數(shù))

--- a/uboot-repo/bl33/board/amlogic/configs/g12a_u202_v1.h
+++ b/uboot-repo/bl33/board/amlogic/configs/g12a_u202_v1.h
@@ -149,6 +149,14 @@
 #define CONFIG_LOGO_FB        "setenv fb_width 800; setenv fb_height 1280;"
 #endif

+#ifndef CONFIG_CONSOLE_LOGLEVEL
+#define CONFIG_CONSOLE_LOGLEVEL "console_loglevel=7\0"
+#endif
+
 /* args/envs */
 #define CONFIG_SYS_MAXARGS  64
 #define CONFIG_EXTRA_ENV_SETTINGS \
@@ -193,6 +201,8 @@
         "lock=10001000\0"\
         "active_slot=normal\0"\
         "boot_part=boot\0"\
+        CONFIG_CONSOLE_LOGLEVEL \
         "reboot_mode_android=""normal""\0"\
         "Irq_check_en=0\0"\
         "fs_type=""rootfstype=ramfs""\0"\
@@ -206,7 +216,7 @@
             "else fi;"\
             "\0"\
         "storeargs="\
-            "setenv bootargs ${initargs} ${fs_type} otg_device=${otg_device} reboot_mode_android=${reboot_mode_android} logo=${display_layer},loaded,${fb_addr} fb_width=${fb_width} fb_height=${fb_height} vout2=${outputmode2},enable vout=${outputmode},enable panel_type=${panel_type} lcd_ctrl=${lcd_ctrl} hdmitx=${cecconfig},${colorattribute} hdmimode=${hdmimode} frac_rate_policy=${frac_rate_policy} hdmi_read_edid=${hdmi_read_edid} cvbsmode=${cvbsmode} osd_reverse=${osd_reverse} video_reverse=${video_reverse} irq_check_en=${Irq_check_en}  androidboot.selinux=${EnableSelinux} androidboot.firstboot=${firstboot} jtag=${jtag}; "\
+            "setenv bootargs ${initargs} ${fs_type} otg_device=${otg_device} console_loglevel=${console_loglevel} reboot_mode_android=${reboot_mode_android} logo=${display_layer},loaded,${fb_addr} fb_width=${fb_width} fb_height=${fb_height} vout2=${outputmode2},enable vout=${outputmode},enable panel_type=${panel_type} lcd_ctrl=${lcd_ctrl} hdmitx=${cecconfig},${colorattribute} hdmimode=${hdmimode} frac_rate_policy=${frac_rate_policy} hdmi_read_edid=${hdmi_read_edid} cvbsmode=${cvbsmode} osd_reverse=${osd_reverse} video_reverse=${video_reverse} irq_check_en=${Irq_check_en}  androidboot.selinux=${EnableSelinux} androidboot.firstboot=${firstboot} jtag=${jtag}; "\

2. 各層如何獲取和設(shè)置

• booloader層

setenv("console_loglevel", 0);  //設(shè)置Env
getenv("console_loglevel");     //獲取Env

• kernel層獲取Env

--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -124,6 +124,21 @@ static int __control_devkmsg(char *str)
        return -EINVAL;
 }

+static int __init console_loglevel_setup(char *str)
+{
+       int level;
+       pr_info("Peter [console_loglevel_setup] str:%s",str);
+       if(kstrtoint(str, 10, &level))
+               return -1;
+       if(level >= 0 && level <= 15)
+               console_printk[0] = level;
+       else
+               return -1;
+       return 0;
+}
+__setup("console_loglevel=", console_loglevel_setup);
+
+

• system-app層
  可以通過原廠提供的類 com.droidlogic.app.SystemControlManager，獲取Env已經(jīng)進(jìn)行廣播接收封裝，在Wiki--內(nèi)部接口有說(shuō)明

public class SystemControlManager {
    public String getBootenv(String prop, String def);
    public void setBootenv(String prop, String val);
}