From 6dc12ecfb268d2d043f9415156d475278f3f714b Mon Sep 17 00:00:00 2001
From: Sulev-Madis Silber <ketas@si.pri.ee>
Date: Fri, 16 Jan 2026 19:29:19 -0800
Subject: [PATCH] spi: "-S" option for continuous stream from standard input to
 bus

created to allow addressable leds to be driven by abusing spi bus as waveform generator. this might have other uses for similar "permanent" spi transfers

Differential Revision:	https://reviews.freebsd.org/D54734
Reviewed by:	adrian
---
 usr.sbin/spi/spi.8 |  7 +++++++
 usr.sbin/spi/spi.c | 41 +++++++++++++++++++++++++++++++----------
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/usr.sbin/spi/spi.8 b/usr.sbin/spi/spi.8
index c3c041fe8e9..d12b7a510aa 100644
--- a/usr.sbin/spi/spi.8
+++ b/usr.sbin/spi/spi.8
@@ -38,6 +38,7 @@
 .Op Fl d Cm r Ns | Ns Cm w Ns | Ns Cm rw
 .Op Fl f Ar device
 .Op Fl m Ar mode
+.Op Fl S
 .Op Fl s Ar max-speed
 .Nm
 .Op Fl i
@@ -145,6 +146,12 @@ caused the LSB to be transmitted and read first.
 SPI mode, 0 through 3.
 This defines the clock phase and timing with respect to reading and writing
 data, as per the SPI specification.
+.It Fl S
+Constantly stream from
+.Xr stdin 3
+to the
+.Nm
+bus.
 .It Fl s Ar speed
 Specify the maximum speed, in Hz, for the SPI clock.
 The bus will operate at its highest available speed which does not
diff --git a/usr.sbin/spi/spi.c b/usr.sbin/spi/spi.c
index 351474dde0b..1ced2371e3d 100644
--- a/usr.sbin/spi/spi.c
+++ b/usr.sbin/spi/spi.c
@@ -129,7 +129,7 @@ usage(void)
 	fputs(" - communicate on SPI bus with slave devices\n"
 	      "Usage:\n"
 	      "        spi [-f device] [-d r|w|rw] [-m mode] [-s max-speed] [-c count]\n"
-	      "            [-C \"command bytes\"] [-A] [-b] [-L] [-v]\n"
+	      "            [-C \"command bytes\"] [-A] [-b] [-L] [-S] [-v]\n"
 	      "        spi -i [-f device] [-v]\n"
 	      "        spi -h\n"
 	      " where\n"
@@ -145,6 +145,7 @@ usage(void)
 	      "        -i query information about the device\n"
 	      "        -A uses ASCII for input/output as 2-digit hex values\n"
 	      "        -b Override output format as binary (only valid with '-A')\n"
+	      "        -S constantly stream from stdin to bus\n"
 	      "        -v verbose output\n"
 	      "        -h prints this message\n"
 	      "\n"
@@ -158,11 +159,12 @@ int
 main(int argc, char *argv[], char *envp[] __unused)
 {
 	struct spi_options opt;
-	int err, ch, hdev, finfo, fdir;
+	int err, ch, hdev, finfo, stream, fdir;
 	char *pstr;
 	char dev_name[PATH_MAX * 2 + 5];
 
 	finfo = 0;
+	stream = 0;
 	fdir = DIR_NONE;
 
 	hdev = -1;
@@ -180,7 +182,7 @@ main(int argc, char *argv[], char *envp[] __unused)
 	opt.ncmd = 0;
 	opt.pcmd = NULL;
 
-	while (!err && (ch = getopt(argc, argv, "f:d:m:s:c:C:AbLvih")) != -1) {
+	while (!err && (ch = getopt(argc, argv, "f:d:m:s:c:C:AbLviSh")) != -1) {
 		switch (ch) {
 		case 'd':
 			if (optarg[0] == 'r') {
@@ -275,6 +277,10 @@ main(int argc, char *argv[], char *envp[] __unused)
 			finfo = 1;
 			break;
 
+		case 'S':
+			stream = 1;
+			break;
+
 		default:
 			err = 1;
 			/* FALLTHROUGH */
@@ -358,14 +364,29 @@ main(int argc, char *argv[], char *envp[] __unused)
 
 	/* do data transfer */
 
-	if (fdir == DIR_READ) {
-		err = perform_read(hdev, &opt);
+	if (stream) {
+		while (!err && !feof(stdin)) {
+			if (fdir == DIR_READ) {
+				err = perform_read(hdev, &opt);
+			}
+			else if (fdir == DIR_WRITE) {
+				err = perform_write(hdev, &opt);
+			}
+			else if (fdir == DIR_READWRITE) {
+				err = perform_readwrite(hdev, &opt);
+			}
+		}
 	}
-	else if (fdir == DIR_WRITE) {
-		err = perform_write(hdev, &opt);
-	}
-	else if (fdir == DIR_READWRITE) {
-		err = perform_readwrite(hdev, &opt);
+	else {
+		if (fdir == DIR_READ) {
+			err = perform_read(hdev, &opt);
+		}
+		else if (fdir == DIR_WRITE) {
+			err = perform_write(hdev, &opt);
+		}
+		else if (fdir == DIR_READWRITE) {
+			err = perform_readwrite(hdev, &opt);
+		}
 	}
 
 the_end: