ANDROID: of: Support CONFIG_CMDLINE_EXTEND config option

The old logic assumes CMDLINE_FROM_BOOTLOADER vs. CMDLINE_FORCE and
ignores CMDLINE_EXTEND.  Here's the old logic:

- CONFIG_CMDLINE_FORCE=true
    CONFIG_CMDLINE
- dt bootargs=non-empty:
    dt bootargs
- dt bootargs=empty, @data is non-empty string
    @data is left unchanged
- dt bootargs=empty, @data is empty string
    CONFIG_CMDLINE (or "" if that's not defined)

The new logic is now documented in of_fdt.h and is copied here for
reference:

- CONFIG_CMDLINE_FORCE=true
    CONFIG_CMDLINE
- CONFIG_CMDLINE_EXTEND=true, @data is non-empty string
    @data + dt bootargs (even if dt bootargs are empty)
- CONFIG_CMDLINE_EXTEND=true, @data is empty string
    CONFIG_CMDLINE + dt bootargs (even if dt bootargs are empty)
- CMDLINE_FROM_BOOTLOADER=true, dt bootargs=non-empty:
    dt bootargs
- CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is non-empty string
    @data is left unchanged
- CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is empty string
    CONFIG_CMDLINE (or "" if that's not defined)

Signed-off-by: Doug Anderson <dianders@chromium.org>
CC: devicetree-discuss@lists.ozlabs.org
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Rob Herring <rob.herring@calxeda.com>
Bug: 120440972
Change-Id: I40ace250847f813358125dfcaa8998fd32cf7ea3
Signed-off-by: Colin Cross <ccross@android.com>
[AmitP: Folded following android-4.9 commit changes into this patch
        e820270abb ("ANDROID: of: fix CONFIG_CMDLINE_EXTEND")
        9a4a740554 ("ANDROID: of: Fix build warnings")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

drivers/of/fdt.c

@@ -1072,42 +1072,66 @@ int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
 	return 0;
 }
 
+/*
+ * Convert configs to something easy to use in C code
+ */
+#if defined(CONFIG_CMDLINE_FORCE)
+static const int overwrite_incoming_cmdline = 1;
+static const int read_dt_cmdline;
+static const int concat_cmdline;
+#elif defined(CONFIG_CMDLINE_EXTEND)
+static const int overwrite_incoming_cmdline;
+static const int read_dt_cmdline = 1;
+static const int concat_cmdline = 1;
+#else /* CMDLINE_FROM_BOOTLOADER */
+static const int overwrite_incoming_cmdline;
+static const int read_dt_cmdline = 1;
+static const int concat_cmdline;
+#endif
+
+#ifdef CONFIG_CMDLINE
+static const char *config_cmdline = CONFIG_CMDLINE;
+#else
+static const char *config_cmdline = "";
+#endif
+
 int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data)
 {
-	int l;
+	int l = 0;
-	const char *p;
+	const char *p = NULL;
+	char *cmdline = data;
 
 	pr_debug("search \"chosen\", depth: %d, uname: %s\n", depth, uname);
 
-	if (depth != 1 || !data ||
+	if (depth != 1 || !cmdline ||
 	    (strcmp(uname, "chosen") != 0 && strcmp(uname, "chosen@0") != 0))
 		return 0;
 
 	early_init_dt_check_for_initrd(node);
 
-	/* Retrieve command line */
+	/* Put CONFIG_CMDLINE in if forced or if data had nothing in it to start */
-	p = of_get_flat_dt_prop(node, "bootargs", &l);
+	if (overwrite_incoming_cmdline || !cmdline[0])
-	if (p != NULL && l > 0)
+		strlcpy(cmdline, config_cmdline, COMMAND_LINE_SIZE);
-		strlcpy(data, p, min((int)l, COMMAND_LINE_SIZE));
 
-	/*
+	/* Retrieve command line unless forcing */
-	 * CONFIG_CMDLINE is meant to be a default in case nothing else
+	if (read_dt_cmdline)
-	 * managed to set the command line, unless CONFIG_CMDLINE_FORCE
+		p = of_get_flat_dt_prop(node, "bootargs", &l);
-	 * is set in which case we override whatever was found earlier.
+
-	 */
+	if (p != NULL && l > 0) {
-#ifdef CONFIG_CMDLINE
+		if (concat_cmdline) {
-#if defined(CONFIG_CMDLINE_EXTEND)
+			int cmdline_len;
-	strlcat(data, " ", COMMAND_LINE_SIZE);
+			int copy_len;
-	strlcat(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+			strlcat(cmdline, " ", COMMAND_LINE_SIZE);
-#elif defined(CONFIG_CMDLINE_FORCE)
+			cmdline_len = strlen(cmdline);
-	strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+			copy_len = COMMAND_LINE_SIZE - cmdline_len - 1;
-#else
+			copy_len = min((int)l, copy_len);
-	/* No arguments from boot loader, use kernel's  cmdl*/
+			strncpy(cmdline + cmdline_len, p, copy_len);
-	if (!((char *)data)[0])
+			cmdline[cmdline_len + copy_len] = '\0';
-		strlcpy(data, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+		} else {
-#endif
+			strlcpy(cmdline, p, min((int)l, COMMAND_LINE_SIZE));
-#endif /* CONFIG_CMDLINE */
+		}
+	}
 
 	pr_debug("Command line is: %s\n", (char*)data);
 

include/linux/of_fdt.h

@@ -69,6 +69,27 @@ extern unsigned long of_get_flat_dt_root(void);
 extern int of_get_flat_dt_size(void);
 extern uint32_t of_get_flat_dt_phandle(unsigned long node);
 
+/*
+ * early_init_dt_scan_chosen - scan the device tree for ramdisk and bootargs
+ *
+ * The boot arguments will be placed into the memory pointed to by @data.
+ * That memory should be COMMAND_LINE_SIZE big and initialized to be a valid
+ * (possibly empty) string.  Logic for what will be in @data after this
+ * function finishes:
+ *
+ * - CONFIG_CMDLINE_FORCE=true
+ *     CONFIG_CMDLINE
+ * - CONFIG_CMDLINE_EXTEND=true, @data is non-empty string
+ *     @data + dt bootargs (even if dt bootargs are empty)
+ * - CONFIG_CMDLINE_EXTEND=true, @data is empty string
+ *     CONFIG_CMDLINE + dt bootargs (even if dt bootargs are empty)
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=non-empty:
+ *     dt bootargs
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is non-empty string
+ *     @data is left unchanged
+ * - CMDLINE_FROM_BOOTLOADER=true, dt bootargs=empty, @data is empty string
+ *     CONFIG_CMDLINE (or "" if that's not defined)
+ */
 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);
 extern int early_init_dt_scan_memory(unsigned long node, const char *uname,