linux-kernel - [PATCH 2/2] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node, take 2

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Message-Id: <20230103-dt-cmdline-fix-v1-2-7038e88b18b6@kernel.org>
Date:   Tue, 03 Jan 2023 12:00:32 -0600
From:   Rob Herring <robh@...nel.org>
To:     Geoff Levand <geoff@...radead.org>,
        Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node, take 2

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"

Rework early_init_dt_scan_chosen() so that the cmdline config options are
always handled.

[commit msg written by Alexander Sverdlin]
Cc: Alexander Sverdlin <alexander.sverdlin@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Rob Herring <robh@...nel.org>
---
 drivers/of/fdt.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 7b571a631639..4b94bb52671e 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1161,18 +1161,32 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 	if (node < 0)
 		node = fdt_path_offset(fdt, "/chosen@0");
 	if (node < 0)
-		return -ENOENT;
+		/* Handle the cmdline config options even if no /chosen node */
+		goto handle_cmdline;
 
 	chosen_node_offset = node;
 
 	early_init_dt_check_for_initrd(node);
 	early_init_dt_check_for_elfcorehdr(node);
 
+	rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
+	if (rng_seed && l > 0) {
+		add_bootloader_randomness(rng_seed, l);
+
+		/* try to clear seed so it won't be found. */
+		fdt_nop_property(initial_boot_params, node, "rng-seed");
+
+		/* update CRC check value */
+		of_fdt_crc32 = crc32_be(~0, initial_boot_params,
+				fdt_totalsize(initial_boot_params));
+	}
+
 	/* Retrieve command line */
 	p = of_get_flat_dt_prop(node, "bootargs", &l);
 	if (p != NULL && l > 0)
 		strscpy(cmdline, p, min(l, COMMAND_LINE_SIZE));
 
+handle_cmdline:
 	/*
 	 * CONFIG_CMDLINE is meant to be a default in case nothing else
 	 * managed to set the command line, unless CONFIG_CMDLINE_FORCE
@@ -1193,18 +1207,6 @@ int __init early_init_dt_scan_chosen(char *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);
-
-		/* try to clear seed so it won't be found. */
-		fdt_nop_property(initial_boot_params, node, "rng-seed");
-
-		/* update CRC check value */
-		of_fdt_crc32 = crc32_be(~0, initial_boot_params,
-				fdt_totalsize(initial_boot_params));
-	}
-
 	return 0;
 }
 

-- 
2.39.0