[PATCH v3 3/4] mmc-utils: lsmmc: Add mmc list command

[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.

Signed-off-by: Torstein Eide <torsteine+linux@gmail.com>
---
 docs/HOWTO.rst | 12 ++++++++
 lsmmc.c        | 76 +++++++++++++++++++++++++++++++++++++++++++++++++-
 mmc.c          |  6 +++-
 mmc_cmds.h     |  1 +
 4 files changed, 93 insertions(+), 2 deletions(-)

diff --git a/docs/HOWTO.rst b/docs/HOWTO.rst
index 3739a0a..0b486e4 100644
--- a/docs/HOWTO.rst
+++ b/docs/HOWTO.rst
@@ -90,6 +90,18 @@ 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 d42e121..bc43004 100644
--- a/lsmmc.c
+++ b/lsmmc.c
@@ -229,6 +229,39 @@ fallback:
 	return strdup(name);
 }
 
+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_at(const char *dir, const char *name)
 {
@@ -2288,6 +2321,37 @@ static const char *month_name(unsigned int month)
 	return months[month];
 }
 
+static void print_list_entry(struct config *cfg, const char *devname,
+			     const char *blkdev, char *cid)
+{
+	char *mfr;
+	char devnode[32];
+
+	snprintf(devnode, sizeof(devnode), "/dev/%s", blkdev ? blkdev : "?");
+
+	if (cfg->bus == SD) {
+		struct sd_cid c;
+
+		parse_sd_cid(cid, &c);
+		mfr = get_manufacturer(cfg, c.mid);
+		printf("%-14s %-14s SD   %-20s %-10s %u.%u  0x%08x  %u-%s\n",
+		       devname, devnode, mfr ? mfr : "Unlisted", c.pnm,
+		       c.prv_major, c.prv_minor, c.psn, 2000 + c.mdt_year,
+		       month_name(c.mdt_month));
+	} else {
+		struct mmc_cid c;
+
+		parse_mmc_cid(cid, &c);
+		mfr = get_manufacturer(cfg, c.mid);
+		printf("%-14s %-14s MMC  %-20s %-10s %u.%u  0x%08x  %u-%s\n",
+		       devname, devnode, mfr ? mfr : "Unlisted", c.pnm,
+		       c.prv_major, c.prv_minor, c.psn, 1997 + c.mdt_year,
+		       month_name(c.mdt_month));
+	}
+
+	free(mfr);
+}
+
 int do_list(int nargs, char **argv)
 {
 	const char *bus_path = "/sys/bus/mmc/devices";
@@ -2303,6 +2367,12 @@ int do_list(int nargs, char **argv)
 
 	struct config cfg = {};
 
+	/* Probe ids files so any warning appears before table output */
+	cfg.bus = SD;
+	free(get_manufacturer(&cfg, ~0u));
+	cfg.bus = MMC;
+	free(get_manufacturer(&cfg, ~0u));
+
 	while ((ent = readdir(d)) != NULL) {
 		char devpath[PATH_MAX];
 		char resolved[PATH_MAX];
@@ -2319,6 +2389,11 @@ int do_list(int nargs, char **argv)
 		if (!type)
 			continue;
 
+		if (strcmp(type, "MMC") != 0 && strcmp(type, "SD") != 0) {
+			free(type);
+			continue;
+		}
+
 		cid = read_file_at(resolved, "cid");
 		if (!cid) {
 			free(type);
@@ -2346,7 +2421,6 @@ int do_list(int nargs, char **argv)
 	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 fce7eef..b0f1f9b 100644
--- a/mmc.c
+++ b/mmc.c
@@ -306,6 +306,11 @@ static struct Command commands[] = {
 	  "3. Only up to 512K bytes of boot data will be transferred.\n"
 	  "4. The MMC will perform a soft reset, if your system cannot handle that do not use the boot operation from mmc-utils.\n",
 	},
+	{ do_list, 0,
+	  "list", "\n"
+		"List all MMC/SD devices with their /dev path and CID info.",
+	  NULL
+	},
 	{ NULL, 0, NULL, NULL }
 };
 
@@ -590,4 +595,3 @@ int main(int ac, char **av )
 
 	exit(func(nargs, args));
 }
-
diff --git a/mmc_cmds.h b/mmc_cmds.h
index 9d5f944..033cc09 100644
--- a/mmc_cmds.h
+++ b/mmc_cmds.h
@@ -62,6 +62,7 @@ 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