Android uses cmdline to pass Parameters from preloader to kernel

Android uses cmdline to pass Parameters from preloader to kernel
Take the definition parameter cus_param as an example, int type variable.

1. Preloader part
Platform. h (mediatek \ platform \ [$ platform] \ preloader \ src \ drivers \ inc \ platform. h)
Add the cus_param variable to the following struct. If it is of the char type, pay attention to it by 4 Bytes:
Typedef struct {
U32 magic;
Boot_mode_t mode;
U32 e_flag;
U32 log_port;
U32 log_baudrate;
U8 log_enable;
U8 part_num;
U8 reserved [2];
U32 dram_rank_num;
U32 dram_rank_size [4];
U32 boot_reason;
U32 meta_com_type;
U32 meta_com_id;
U32 boot_time;
Da_info_t da_info;
SEC_LIMIT sec_limit;
Part_hdr_t * part_info;
U8 md_type [4];
U32 ddr_reserve_enable;
U32 ddr_reserve_success;
U32 cus_param; // mediatek add
} Boot_arg_t;

Platform. c (mediatek \ platform \ [$ platform] \ preloader \ src \ drivers \ platform. c)
Add a value for cus_param to this function. Use the function or directly write the required value:
Void platform_set_boot_args ()
{
# If cmd_boot_argument
Bootarg. magic = BOOT_ARGUMENT_MAGIC;
Bootarg. mode = g_boot_mode;
Bootarg. e_flag = sp_check_platform ();
Bootarg. log_port = pai_uart_log;
Bootarg. log_baudrate = pai_log_baudrate;
Bootarg. log_enable = (u8) log_status ();
Bootarg. dram_rank_num = get_dram_rank_nr ();
Get_dram_rank_size (bootarg. dram_rank_size );
Bootarg. boot_reason = g_boot_reason;
Bootarg. meta_com_type = (u32) g_meta_com_type;
Bootarg. meta_com_id = g_meta_com_id;
Bootarg. boot_time = get_timer (g_boot_time );

Bootarg. part_num = g_dram_buf-> part_num;
Bootarg. part_info = g_dram_buf-> part_info;

Bootarg. ddr_reserve_enable = g_ddr_reserve_enable;
Bootarg. ddr_reserve_success = g_ddr_reserve_success;

// Mediatek add, mt_get_cus_param. This function is customized to obtain the cus_param function. Please implement it by yourself.
Bootarg. cus_param = mt_get_cus_param ();

2. LK part
Boot_mode.h (mediatek \ platform \ [$ platform] \ lk \ include \ platform \ boot_mode.h)
Add the cus_param variable to the following struct. If it is char type, pay attention to it by 4 Bytes:
Typedef struct {
U32 maggic_number;
BOOTMODE boot_mode;
U32 e_flag;
U32 log_port;
U32 log_baudrate;
U8 log_enable;
U8 part_num;
U8 reserved [2];
U32 dram_rank_num;
U32 dram_rank_size [4];
U32 boot_reason;
META_COM_TYPE meta_com_type;
U32 meta_com_id;
U32 boot_time;
Da_info_t da_info;
SEC_LIMIT sec_limit;
Part_hdr_t * part_info;
U8 md_type [4];
U32 ddr_reserve_enable;
U32 ddr_reserve_success;
U32 cus_param; // mediatek add, which is the same as the preloader and must be the same as the two struct.
} BOOT_ARGUMENT;

Mt_boot.c (bootable \ bootloader \ lk \ app \ mt_boot \ mt_boot.c)
In this function, add the information of cus_param to cmdline:
Int boot_linux_from_storage (void)
{
.....
Strlen + = sprintf (commanline, "% s fps = % 1d", commanline, mt_disp_get_ LCD _time ());
Strlen + = sprintf (commanline, "% s cus_param = % 1d", commanline, g_boot_arg-> cus_param); // mediatek add

3. Kernel Section
Saved_command_line this is a global variable. In the driver file where you need this parameter, extern saved_command_line variable,
Search for the string of cus_param:
Char * ptr;
Int cus_param;
Ptr = strstr (saved_command_line, "cus_param = ");
Ptr + = strlen ("cus_param = ");
Cus_param = simple_strtol (ptr, NULL, 10 );
In this case, cus_param is the initial int value.