[PATCH v4 3/3] cmd: rng: Add rng list command

[Weizhao Ouyang <o451686892@gmail.com>]

The 'rng list' command probes all RNG devices and list those devices
that are successfully probed. Also update the help info.

Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
---
v4: update doc/usage/cmd/rng.rst
---
 cmd/rng.c             | 23 ++++++++++++++++++-----
 doc/usage/cmd/rng.rst | 14 ++++++++++----
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/cmd/rng.c b/cmd/rng.c
index 52f722c7af..b073a6c849 100644
--- a/cmd/rng.c
+++ b/cmd/rng.c
@@ -19,6 +19,22 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	struct udevice *dev;
 	int ret = CMD_RET_SUCCESS;
 
+	if (argc == 2 && !strcmp(argv[1], "list")) {
+		int idx = 0;
+
+		uclass_foreach_dev_probe(UCLASS_RNG, dev) {
+			idx++;
+			printf("RNG #%d - %s\n", dev->seq_, dev->name);
+		}
+
+		if (!idx) {
+			log_err("No RNG device\n");
+			return CMD_RET_FAILURE;
+		}
+
+		return CMD_RET_SUCCESS;
+	}
+
 	switch (argc) {
 	case 1:
 		devnum = 0;
@@ -56,12 +72,9 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	return ret;
 }
 
-U_BOOT_LONGHELP(rng,
-	"[dev [n]]\n"
-	"  - print n random bytes(max 64) read from dev\n");
-
 U_BOOT_CMD(
 	rng, 3, 0, do_rng,
 	"print bytes from the hardware random number generator",
-	rng_help_text
+	"list         - list all the probed rng devices\n"
+	"rng [dev] [n]    - print n random bytes(max 64) read from dev\n"
 );
diff --git a/doc/usage/cmd/rng.rst b/doc/usage/cmd/rng.rst
index 274e4d88df..4a61e33d27 100644
--- a/doc/usage/cmd/rng.rst
+++ b/doc/usage/cmd/rng.rst
@@ -11,16 +11,22 @@ Synopsis
 
 ::
 
-    rng [devnum [n]]
+    rng list
+    rng [dev] [n]
 
-Description
------------
+rng list
+--------
+
+List all the probed rng devices.
+
+rng [dev] [n]
+-------------
 
 The *rng* command reads the random number generator(RNG) device and
 prints the random bytes read on the console. A maximum of 64 bytes can
 be read in one invocation of the command.
 
-devnum
+dev
     The RNG device from which the random bytes are to be
     read. Defaults to 0.
 
-- 
2.40.1