Amlogic 905平台Env环境在Android系统各层获取

需要在各层如：bootloader、kernel、framework、system-app获取uboot的Env需要如下步骤
以905平台设置控制台日志等级为例

1. 将Env环境变量预置并且作为bootargs(传递给内核的启动参数)

--- 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. 各层如何获取和设置

• booloader层

setenv("console_loglevel", 0);  //设置Env
getenv("console_loglevel");     //获取Env

• kernel层获取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层
  可以通过原厂提供的类 com.droidlogic.app.SystemControlManager，获取Env已经进行广播接收封装，在Wiki--内部接口有说明

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