[PATCH 1/1] mmc-utils: lsmmc: Add 'mmc list' command

[Torstein Eide <torsteine@gmail.com>]

From: Torstein EIde <torsteine+linux@gmail.com>

Add a 'mmc list' command that scans /sys/bus/mmc/devices/, resolves
each card's sysfs path, and prints a one-line summary per device.

find_block_devname() maps a sysfs device path back to its mmcblkN
name by scanning /sys/class/block/mmcblkN/device symlinks.

print_list_entry() parses the CID register and formats a fixed-width
table row with device name, /dev path, bus type, manufacturer, product,
revision, serial number, and manufacturing date.

The header is printed once before the first result. Devices without a
readable cid file are skipped silently via access() so unrelated sysfs
entries do not produce spurious error messages.
---
 docs/HOWTO.rst |   5 ++
 lsmmc.c        | 162 +++++++++++++++++++++++++++++++++++++++++++++++++
 mmc.c          |   5 ++
 mmc_cmds.h     |   1 +
 4 files changed, 173 insertions(+)

diff --git a/docs/HOWTO.rst b/docs/HOWTO.rst
index 02edea4..45c440b 100644
--- a/docs/HOWTO.rst
+++ b/docs/HOWTO.rst
@@ -84,6 +84,11 @@ Running mmc-utils
             sysfs: /sys/devices/platform/fe320000.mmc/mmc_host/mmc1/mmc1:aaaa
             SCR Register: 0235800000000000
 
+    ``list``
+        List all MMC/SD devices present on the system. Output is a table with
+        columns: DEVICE (sysfs name), DEV (/dev path), TYPE (MMC or SD),
+        MANUFACTURER, PRODUCT, REV, SERIAL, and DATE.
+
+        Example::
+
+            $ mmc list
+            DEVICE          DEV            TYPE  MANUFACTURER         PRODUCT     REV    SERIAL      DATE
+            mmc0:0001       /dev/mmcblk0   MMC   Samsung              MAG4FA      1.0    0x1a2b3c4d  2021-jan
+            mmc1:aaaa       /dev/mmcblk1   SD    SanDisk              SP32G       8.0    0x5e6f7a8b  2020-mar
+
     ``ffu <image name> <device> [chunk-bytes]``
       Default mode.  Run Field Firmware Update with `<image name>` on `<device>`. `[chunk-bytes]` is optional and defaults to its max - 512k. Should be in decimal bytes and sector aligned.
 
diff --git a/lsmmc.c b/lsmmc.c
index e33d636..ec79841 100644
--- a/lsmmc.c
+++ b/lsmmc.c
@@ -252,6 +252,38 @@ static char *resolve_dev_path(const char *path)
 	return resolved;
 }
 
+static char *find_block_devname(const char *sysfs_devpath)
+{
+	DIR *d;
+	struct dirent *ent;
+
+	d = opendir("/sys/class/block");
+	if (!d)
+		return NULL;
+
+	while ((ent = readdir(d)) != NULL) {
+		char linkpath[PATH_MAX];
+		char resolved[PATH_MAX];
+
+		if (strncmp(ent->d_name, "mmcblk", 6) != 0)
+			continue;
+		if (strchr(ent->d_name + 6, 'p'))
+			continue;
+
+		snprintf(linkpath, sizeof(linkpath),
+			 "/sys/class/block/%s/device", ent->d_name);
+		if (realpath(linkpath, resolved) == NULL)
+			continue;
+		if (strcmp(resolved, sysfs_devpath) == 0) {
+			closedir(d);
+			return strdup(ent->d_name);
+		}
+	}
+
+	closedir(d);
+	return NULL;
+}
+
 /* MMC/SD file parsing functions */
 static char *read_file(char *name)
 {
@@ -2197,6 +2229,136 @@ static int do_read_reg(int argc, char **argv, enum REG_TYPE reg)
 	return ret;
 }
 
+static void print_list_entry(struct config *cfg, const char *devname,
+			     const char *blkdev, char *cid)
+{
+	static const char *months[] = {
+		"jan", "feb", "mar", "apr", "may", "jun",
+		"jul", "aug", "sep", "oct", "nov", "dec",
+		"???", "???", "???", "???",
+	};
+	const char *mfr;
+	char devnode[32];
+
+	snprintf(devnode, sizeof(devnode), "/dev/%s", blkdev ? blkdev : "?");
+
+	if (cfg->bus == SD) {
+		unsigned int mid, prv_major, prv_minor, psn, mdt_year, mdt_month, crc;
+		char oid[3], pnm[6];
+
+		parse_bin(cid, "8u16a40a4u4u32u4r8u4u7u1r",
+			  &mid, &oid[0], &pnm[0],
+			  &prv_major, &prv_minor, &psn,
+			  &mdt_year, &mdt_month, &crc);
+		oid[2] = '\0';
+		pnm[5] = '\0';
+
+		mfr = get_manufacturer(cfg, mid);
+		printf("%-14s %-14s SD   %-20s %-10s %u.%u  0x%08x  %u-%s\n",
+		       devname, devnode,
+		       mfr ? mfr : "Unlisted",
+		       pnm, prv_major, prv_minor,
+		       psn, 2000 + mdt_year, months[mdt_month]);
+	} else {
+		unsigned int mid, cbx, oid, prv_major, prv_minor, psn;
+		unsigned int mdt_year, mdt_month, crc;
+		char pnm[7];
+
+		parse_bin(cid, "8u6r2u8u48a4u4u32u4u4u7u1r",
+			  &mid, &cbx, &oid, &pnm[0],
+			  &prv_major, &prv_minor, &psn,
+			  &mdt_year, &mdt_month, &crc);
+		pnm[6] = '\0';
+
+		mfr = get_manufacturer(cfg, mid);
+		printf("%-14s %-14s MMC  %-20s %-10s %u.%u  0x%08x  %u-%s\n",
+		       devname, devnode,
+		       mfr ? mfr : "Unlisted",
+		       pnm, prv_major, prv_minor,
+		       psn, 1997 + mdt_year, months[mdt_month]);
+	}
+}
+
+int do_list(int nargs, char **argv)
+{
+	const char *bus_path = "/sys/bus/mmc/devices";
+	char orig_cwd[PATH_MAX];
+	DIR *d;
+	struct dirent *ent;
+	bool header_printed = false;
+
+	if (!getcwd(orig_cwd, sizeof(orig_cwd))) {
+		fprintf(stderr, "Cannot get current directory.\n");
+		return -1;
+	}
+
+	d = opendir(bus_path);
+	if (!d) {
+		fprintf(stderr, "Cannot open %s\n", bus_path);
+		return -1;
+	}
+
+	while ((ent = readdir(d)) != NULL) {
+		char devpath[PATH_MAX];
+		char resolved[PATH_MAX];
+		char *type, *cid, *blkdev;
+		struct config cfg = {};
+
+		if (!strchr(ent->d_name, ':'))
+			continue;
+
+		snprintf(devpath, sizeof(devpath), "%s/%s", bus_path, ent->d_name);
+		if (realpath(devpath, resolved) == NULL)
+			continue;
+
+		if (chdir(resolved) < 0)
+			continue;
+
+		if (access("cid", R_OK) != 0) {
+			if (chdir(orig_cwd) < 0)
+				break;
+			continue;
+		}
+
+		type = read_file("type");
+		if (!type) {
+			if (chdir(orig_cwd) < 0)
+				break;
+			continue;
+		}
+
+		cid = read_file("cid");
+		if (!cid) {
+			free(type);
+			if (chdir(orig_cwd) < 0)
+				break;
+			continue;
+		}
+
+		blkdev = find_block_devname(resolved);
+		cfg.bus = strcmp(type, "MMC") ? SD : MMC;
+		cfg.ids_dir = orig_cwd;
+
+		if (!header_printed) {
+			printf("%-14s %-14s %-5s%-20s %-10s %-5s %-12s %s\n",
+			       "DEVICE", "DEV", "TYPE", "MANUFACTURER",
+			       "PRODUCT", "REV", "SERIAL", "DATE");
+			header_printed = true;
+		}
+
+		print_list_entry(&cfg, ent->d_name, blkdev, cid);
+
+		free(blkdev);
+		free(cid);
+		free(type);
+		if (chdir(orig_cwd) < 0)
+			break;
+	}
+
+	closedir(d);
+	return 0;
+}
+
 int do_read_csd(int argc, char **argv)
 {
 	return do_read_reg(argc, argv, CSD);
diff --git a/mmc.c b/mmc.c
index 077e901..0953bef 100644
--- a/mmc.c
+++ b/mmc.c
@@ -292,6 +292,11 @@ static struct Command commands[] = {
 	  "4. The MMC will perform a soft reset, if your system cannot handle that do not use the boot operation from mmc-utils.\n",
 	  NULL
 	},
+	{ do_list, 0,
+	  "list", "\n"
+		"List all MMC/SD devices with their /dev path and CID info.",
+	  NULL
+	},
 	{ NULL, 0, NULL, NULL }
 };
 
diff --git a/mmc_cmds.h b/mmc_cmds.h
index 407cbe6..508776c 100644
--- a/mmc_cmds.h
+++ b/mmc_cmds.h
@@ -49,6 +49,7 @@ int do_opt_ffu4(int nargs, char **argv);
 int do_read_scr(int argc, char **argv);
 int do_read_cid(int argc, char **argv);
 int do_read_csd(int argc, char **argv);
+int do_list(int nargs, char **argv);
 int do_erase(int nargs, char **argv);
 int do_general_cmd_read(int nargs, char **argv);
 int do_softreset(int nargs, char **argv);
-- 
2.53.0