From a08f08ec675261a7d7c141f818a613a304e85be8 Mon Sep 17 00:00:00 2001
From: Sean Anderson <sean.anderson@seco.com>
Date: Fri, 16 Dec 2022 11:16:25 -0500
Subject: [PATCH] mmc-utils: Add a command to write extcsd registers

There is a command to read the extcsd and some commands to configure
particular features, but no generic write extcsd command. Such a command
may be useful for not-yet-supported features and manufacturer-specific
registers.

Signed-off-by: Philippe Reynes <philippe.reynes@sagemcom.com>
[ rebased onto latest master and updated commit message ]
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/20221216161625.2924013-1-sean.anderson@seco.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 mmc.c      |  5 +++++
 mmc_cmds.c | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/mmc.c b/mmc.c
index adcd814..b9aa478 100644
--- a/mmc.c
+++ b/mmc.c
@@ -58,6 +58,11 @@ static struct Command commands[] = {
 		"Print extcsd data from <device>.",
 	  NULL
 	},
+	{ do_write_extcsd, 3,
+	  "extcsd write", "<offset> <value> <device>\n"
+		  "Write <value> at offset <offset> to <device>'s extcsd.",
+	  NULL
+	},
 	{ do_writeprotect_boot_get, -1,
 	  "writeprotect boot get", "<device>\n"
 		"Print the boot partitions write protect status for <device>.",
diff --git a/mmc_cmds.c b/mmc_cmds.c
index e6d3273..33b9e43 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -1982,6 +1982,38 @@ out_free:
 	return ret;
 }
 
+int do_write_extcsd(int nargs, char **argv)
+{
+	int fd, ret;
+	int offset, value;
+	char *device;
+
+	if (nargs != 4) {
+		fprintf(stderr, "Usage: mmc extcsd write <offset> <value> </path/to/mmcblkX>\n");
+		exit(1);
+	}
+
+	offset = strtol(argv[1], NULL, 0);
+	value  = strtol(argv[2], NULL, 0);
+	device = argv[3];
+
+	fd = open(device, O_RDWR);
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+
+	ret = write_extcsd_value(fd, offset, value, 0);
+	if (ret) {
+		fprintf(stderr,
+			"Could not write 0x%02x to EXT_CSD[%d] in %s\n",
+			value, offset, device);
+		exit(1);
+	}
+
+	return ret;
+}
+
 int do_sanitize(int nargs, char **argv)
 {
 	int fd, ret;