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

@@ -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

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: