linux-kernel - [PATCH] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node

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Date:   Mon, 12 Dec 2022 00:58:17 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...il.com>
To:     devicetree@...r.kernel.org
Cc:     Linus Walleij <linusw@...nel.org>
Subject: [PATCH] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node

I do not read a strict requirement on /chosen node in either ePAPR or in
Documentation/devicetree. Help text for CONFIG_CMDLINE and
CONFIG_CMDLINE_EXTEND doesn't make their behavior explicitly dependent on
the presence of /chosen or the presense of /chosen/bootargs.

However the early check for /chosen and bailing out in
early_init_dt_scan_chosen() skips CONFIG_CMDLINE handling which is not
really related to /chosen node or the particular method of passing cmdline
from bootloader.

This leads to counterintuitive combinations (assuming
CONFIG_CMDLINE_EXTEND=y):

a) bootargs="foo", CONFIG_CMDLINE="bar" => cmdline=="foo bar"
b) /chosen missing, CONFIG_CMDLINE="bar" => cmdline==""
c) bootargs="", CONFIG_CMDLINE="bar" => cmdline==" bar"

Move CONFIG_CMDLINE handling outside of early_init_dt_scan_chosen() so that
cases b and c above result in the same cmdline.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...il.com>
---
 drivers/of/fdt.c | 40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 7b571a631639..b2272bccf85c 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1173,26 +1173,6 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 	if (p != NULL && l > 0)
 		strscpy(cmdline, p, min(l, COMMAND_LINE_SIZE));
 
-	/*
-	 * CONFIG_CMDLINE is meant to be a default in case nothing else
-	 * managed to set the command line, unless CONFIG_CMDLINE_FORCE
-	 * is set in which case we override whatever was found earlier.
-	 */
-#ifdef CONFIG_CMDLINE
-#if defined(CONFIG_CMDLINE_EXTEND)
-	strlcat(cmdline, " ", COMMAND_LINE_SIZE);
-	strlcat(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
-#elif defined(CONFIG_CMDLINE_FORCE)
-	strscpy(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
-#else
-	/* No arguments from boot loader, use kernel's  cmdl*/
-	if (!((char *)cmdline)[0])
-		strscpy(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
-#endif
-#endif /* CONFIG_CMDLINE */
-
-	pr_debug("Command line is: %s\n", (char *)cmdline);
-
 	rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
 	if (rng_seed && l > 0) {
 		add_bootloader_randomness(rng_seed, l);
@@ -1297,6 +1277,26 @@ void __init early_init_dt_scan_nodes(void)
 	if (rc)
 		pr_warn("No chosen node found, continuing without\n");
 
+	/*
+	 * CONFIG_CMDLINE is meant to be a default in case nothing else
+	 * managed to set the command line, unless CONFIG_CMDLINE_FORCE
+	 * is set in which case we override whatever was found earlier.
+	 */
+#ifdef CONFIG_CMDLINE
+#if defined(CONFIG_CMDLINE_EXTEND)
+	strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+	strlcat(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+#elif defined(CONFIG_CMDLINE_FORCE)
+	strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+#else
+	/* No arguments from boot loader, use kernel's cmdl */
+	if (!boot_command_line[0])
+		strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+#endif
+#endif /* CONFIG_CMDLINE */
+
+	pr_debug("Command line is: %s\n", boot_command_line);
+
 	/* Setup memory, calling early_init_dt_add_memory_arch */
 	early_init_dt_scan_memory();
 
-- 
2.37.3