LK把相关参数报存到cmdline上：
在Bootable\bootloader\lk\dev\gcdb\display\gcdb_display_param.c上gcdb_display_cmdline_arg函数里：
调用过程如图所示：
aboot_init()--> target_display_panel_node()--> gcdb_display_cmdline_arg(panel_name, pbuf, buf_size)
aboot_init()函数里面：
#define DISPLAY_DEFAULT_PREFIX "mdss_mdp"
..........
if (cmdline) {
if ((strstr(cmdline, DISPLAY_DEFAULT_PREFIX) == NULL) &&
target_display_panel_node(device.display_panel,
display_panel_buf, MAX_PANEL_BUF_SIZE) &&
strlen(display_panel_buf)) {
cmdline_len += strlen(display_panel_buf);
}
}
target_display_panel_node()函数里面：
bool gcdb_display_cmdline_arg(char *panel_name, char *pbuf, uint16_t buf_size)
{
char *dsi_id = NULL;
char *panel_node = NULL;
char *slave_panel_node = NULL;
uint16_t dsi_id_len = 0, panel_node_len = 0, slave_panel_node_len = 0;
uint32_t arg_size = 0;
bool ret = true;
bool rc;
char *default_str;
int panel_mode = SPLIT_DISPLAY_FLAG | DUAL_PIPE_FLAG | DST_SPLIT_FLAG;
int prefix_string_len = strlen(DISPLAY_CMDLINE_PREFIX);
panel_name += strspn(panel_name, " ");
rc = mdss_dsi_set_panel_node(panel_name, &dsi_id, &panel_node,
&slave_panel_node, &panel_mode);
if (!rc) {
if (panelstruct.paneldata && target_cont_splash_screen()) {
dsi_id = panelstruct.paneldata->panel_controller;
panel_node = panelstruct.paneldata->panel_node_id;
panel_mode =
panelstruct.paneldata->panel_operating_mode &
panel_mode;
slave_panel_node =
panelstruct.paneldata->slave_panel_node_id;
} else {
if (target_is_edp())
default_str = "0:edp:";
else
default_str = "0:dsi:0:";
arg_size = prefix_string_len + strlen(default_str);
if (buf_size < arg_size) {
dprintf(CRITICAL, "display command line buffer is small\n");
return false;
}
strlcpy(pbuf, DISPLAY_CMDLINE_PREFIX, buf_size);
pbuf += prefix_string_len;
buf_size -= prefix_string_len;
strlcpy(pbuf, default_str, buf_size);
return true;
}
}
if (dsi_id == NULL || panel_node == NULL) {
dprintf(CRITICAL, "panel node or dsi ctrl not present\n");
return false;
}
if (panel_mode && slave_panel_node == NULL) {
dprintf(CRITICAL, "slave node not present in dual dsi case\n");
return false;
}
dsi_id_len = strlen(dsi_id);
panel_node_len = strlen(panel_node);
if (!slave_panel_node)
slave_panel_node = NO_PANEL_CONFIG;
slave_panel_node_len = strlen(slave_panel_node);
arg_size = prefix_string_len + dsi_id_len + panel_node_len +
LK_OVERRIDE_PANEL_LEN + 1;
arg_size += DSI_1_STRING_LEN + slave_panel_node_len;
if (buf_size < arg_size) {
dprintf(CRITICAL, "display command line buffer is small\n");
ret = false;
} else {
strlcpy(pbuf, DISPLAY_CMDLINE_PREFIX, buf_size);
pbuf += prefix_string_len;
buf_size -= prefix_string_len;
strlcpy(pbuf, LK_OVERRIDE_PANEL, buf_size);
pbuf += LK_OVERRIDE_PANEL_LEN;
buf_size -= LK_OVERRIDE_PANEL_LEN;
strlcpy(pbuf, dsi_id, buf_size);
pbuf += dsi_id_len;
buf_size -= dsi_id_len;
strlcpy(pbuf, panel_node, buf_size);
pbuf += panel_node_len;
buf_size -= panel_node_len;
strlcpy(pbuf, DSI_1_STRING, buf_size);
pbuf += DSI_1_STRING_LEN;
buf_size -= DSI_1_STRING_LEN;
strlcpy(pbuf, slave_panel_node, buf_size);
}
end:
return ret;
}
最终传给赋值给cmdline的就是从mdss_mdp3.panel=1:dsi:0:qcom,mdss_dsi_tianshan_qhd_video:1:none
kernel获取LK保存的pbuf
调用顺序：
start_kernel()--> setup_arch()--> set_command_line()-->
这是将command_line保存下来：
/**
* mdss_dsi_find_panel_of_node(): find device node of dsi panel
* @pdev: platform_device of the dsi ctrl node
* @panel_cfg: string containing intf specific config data
*
* Function finds the panel device node using the interface
* specific configuration data. This configuration data is
* could be derived from the result of bootloader's GCDB
* panel detection mechanism. If such config data doesn't
* exist then this panel returns the default panel configured
* in the device tree.
*
* returns pointer to panel node on success, NULL on error.
*/
static struct device_node *mdss_dsi_find_panel_of_node(
struct platform_device *pdev, char *panel_cfg)
{
int len, i;
int ctrl_id = pdev->id - 1;
char panel_name[MDSS_MAX_PANEL_LEN];
char ctrl_id_stream[3] = "0:";
char *stream = NULL, *pan = NULL;
struct device_node *dsi_pan_node = NULL, *mdss_node = NULL;
len = strlen(panel_cfg);
if (!len) {
/* no panel cfg chg, parse dt */
pr_debug("%s:%d: no cmd line cfg present\n",
__func__, __LINE__);
goto end;
} else {
if (ctrl_id == 1)
strlcpy(ctrl_id_stream, "1:", 3);
stream = strnstr(panel_cfg, ctrl_id_stream, len);
if (!stream) {
pr_err("controller config is not present\n");
goto end;
}
stream += 2;
pan = strnchr(stream, strlen(stream), ':');
if (!pan) {
strlcpy(panel_name, stream, MDSS_MAX_PANEL_LEN);
} else {
for (i = 0; (stream + i) < pan; i++)
panel_name[i] = *(stream + i);
panel_name[i] = 0;
}
pr_debug("%s:%d:%s:%s\n", __func__, __LINE__,
panel_cfg, panel_name);
mdss_node = of_parse_phandle(pdev->dev.of_node,
"qcom,mdss-mdp", 0);
if (!mdss_node) {
pr_err("%s: %d: mdss_node null\n",
__func__, __LINE__);
return NULL;
}
dsi_pan_node = of_find_node_by_name(mdss_node,
panel_name);
if (!dsi_pan_node) {
pr_err("%s: invalid pan node, selecting prim panel\n",
__func__);
goto end;
}
return dsi_pan_node;
}
end:
//最后如果都没有匹配到的话，就使用这个qcom,dsi-pref-prim-pan节点上的
if (strcmp(panel_name, NONE_PANEL))
dsi_pan_node = mdss_dsi_pref_prim_panel(pdev);
return dsi_pan_node;
}