[PATCH v5 6/9] cmd: rng: Add support for selecting RNG device

[Sughosh Ganu]

The 'rng' u-boot command is used for printing a select number of
random bytes on the console. Currently, the RNG device from which the
random bytes are read is fixed. However, a platform can have multiple
RNG devices, one example being qemu, which has a virtio RNG device and
the RNG pseudo device through the TPM chip.

Extend the 'rng' command so that the user can provide the RNG device
number from which the random bytes are to be read. This will be the
device index under the RNG uclass.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
Tested-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---

Changes since V4:

* Use uclass_get_device_by_seq API to get the RNG device as suggested
  by Simon

 cmd/rng.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/cmd/rng.c b/cmd/rng.c
index 1ad5a096c0..2ddf27545f 100644
--- a/cmd/rng.c
+++ b/cmd/rng.c
@@ -13,19 +13,34 @@
 
 static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 {
-	size_t n = 0x40;
+	size_t n;
 	struct udevice *dev;
 	void *buf;
+	int devnum;
 	int ret = CMD_RET_SUCCESS;
 
-	if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
+	switch (argc) {
+	case 1:
+		devnum = 0;
+		n = 0x40;
+		break;
+	case 2:
+		devnum = hextoul(argv[1], NULL);
+		n = 0x40;
+		break;
+	case 3:
+		devnum = hextoul(argv[1], NULL);
+		n = hextoul(argv[2], NULL);
+		break;
+	default:
+		return CMD_RET_USAGE;
+	}
+
+	if (uclass_get_device_by_seq(UCLASS_RNG, devnum, &dev) || !dev) {
 		printf("No RNG device\n");
 		return CMD_RET_FAILURE;
 	}
 
-	if (argc >= 2)
-		n = hextoul(argv[1], NULL);
-
 	buf = malloc(n);
 	if (!buf) {
 		printf("Out of memory\n");
@@ -46,12 +61,12 @@ static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 
 #ifdef CONFIG_SYS_LONGHELP
 static char rng_help_text[] =
-	"[n]\n"
-	"  - print n random bytes\n";
+	"[dev [n]]\n"
+	"  - print n random bytes read from dev\n";
 #endif
 
 U_BOOT_CMD(
-	rng, 2, 0, do_rng,
+	rng, 3, 0, do_rng,
 	"print bytes from the hardware random number generator",
 	rng_help_text
 );
-- 
2.25.1