Add another convenience wrapper function to the SPI framework.

spi_sendv(spi_handle_t sh, const struct iovec *iov,
    int iovcnt)

Takes a iovec of buffers and sends them as one transaction down the
SPI bus.

There exists devices that will not handle sending the register that is
to be written to as one transaction and the data as a second
transaction.  That is, use one spi_send() to send the register and a
second spi_send() to send the data.  Those devices require a single
transaction with both parts in it.

Author: brad

share/man/man9/spi.9

@@ -1,4 +1,4 @@
-.\"	$NetBSD: spi.9,v 1.2 2019/02/23 17:37:10 wiz Exp $
+.\"	$NetBSD: spi.9,v 1.3 2025/10/10 18:36:17 brad Exp $
 .\"
 .\" Copyright (c) 2019 The NetBSD Foundation
 .\" All rights reserved.
@@ -38,6 +38,7 @@
 .Nm spi_wait ,
 .Nm spi_done ,
 .Nm spi_send ,
+.Nm spi_sendv ,
 .Nm spi_recv ,
 .Nm spi_send_recv
 .Nd Serial Peripheral Interface (SPI) kernel interface
@@ -92,12 +93,18 @@
 .Fa "const uint8_t *data"
 .Fc
 .Ft int
+.Fo spi_sendv
+.Fa "struct spi_handle *sh"
+.Fa "struct iovec *iov"
+.Fa "int iovcnt"
+.Fc
+.Ft int
 .Fo spi_send_recv
 .Fa "struct spi_handle *sh"
 .Fa "int scnt"
 .Fa "const uint8_t *snd"
 .Fa "int rcnt"
-.Fa "const uint8_t *rcv"
+.Fa "uint8_t *rcv"
 .Fc
 .Sh DESCRIPTION
 SPI is a 4-wire synchronous full-duplex serial bus.
@@ -148,6 +155,8 @@ waits for it to complete.
 .It Fn spi_send "sh" "cnt" "data"
 Prepares a chunk for sending data, queues a transfer and
 waits for it to complete.
+.It Fn spi_sendv "sh" "iov" "iovcnt"
+Prepare and queue a scatter of chunks and wait for them to complete.
 .It Fn spi_send_recv "sh" "scnt" "snd" "rcnt" "rcv"
 Prepares two chunks for sending data first and then receiving
 an answer, queues a transfer and waits for it to complete.

sys/dev/spi/spi.c

@@ -1,4 +1,4 @@
-/* $NetBSD: spi.c,v 1.37 2025/09/21 13:02:08 thorpej Exp $ */
+/* $NetBSD: spi.c,v 1.38 2025/10/10 18:36:17 brad Exp $ */
 
 /*-
  * Copyright (c) 2006 Urbana-Champaign Independent Media Center.
@@ -44,18 +44,20 @@
 #include "opt_fdt.h"		/* XXX */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spi.c,v 1.37 2025/09/21 13:02:08 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spi.c,v 1.38 2025/10/10 18:36:17 brad Exp $");
 
 #include "locators.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/device.h>
+#include <sys/kmem.h>
 #include <sys/conf.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/condvar.h>
 #include <sys/errno.h>
+#include <sys/uio.h>
 
 #include <dev/spi/spivar.h>
 #include <dev/spi/spi_io.h>
@@ -686,6 +688,8 @@ spi_done(struct spi_transfer *st, int err)
  * done synchronously, i.e. send a command and get the response.  This is
  * not full duplex.  If you want full duplex, you can't use these convenience
  * wrappers.
+ *
+ * spi_sendv - scatter send data to the bus
  */
 int
 spi_recv(spi_handle_t sh, int cnt, uint8_t *data)
@@ -749,3 +753,38 @@ spi_send_recv(spi_handle_t sh, int scnt, const uint8_t *snd,
 
 	return 0;
 }
+
+int
+spi_sendv(spi_handle_t sh, const struct iovec *iov,
+    int iovcnt)
+{
+	struct spi_transfer	trans;
+	SIMPLEQ_HEAD(,spi_chunk_q) ck_q;
+	struct spi_chunk_q	*ce;
+
+	SIMPLEQ_INIT(&ck_q);
+
+	spi_transfer_init(&trans);
+	for(int c = 0; c < iovcnt;c++) {
+		ce = kmem_alloc(sizeof(struct spi_chunk_q),KM_NOSLEEP);
+		if (ce == NULL)
+			return ENOMEM;
+		spi_chunk_init(&ce->chunk, iov[c].iov_len, iov[c].iov_base, NULL);
+		spi_transfer_add(&trans, &ce->chunk);
+		SIMPLEQ_INSERT_HEAD(&ck_q, ce, chunk_q);
+	}
+
+	/* enqueue it and wait for it to complete */
+	spi_transfer(sh, &trans);
+	spi_wait(&trans);
+
+        while ((ce = SIMPLEQ_FIRST(&ck_q)) != NULL) {
+                SIMPLEQ_REMOVE_HEAD(&ck_q, chunk_q);
+		kmem_free(ce, sizeof(struct spi_chunk_q));
+        }
+
+	if (trans.st_flags & SPI_F_ERROR)
+		return trans.st_errno;
+
+	return 0;
+}

sys/dev/spi/spivar.h

@@ -1,4 +1,4 @@
-/* $NetBSD: spivar.h,v 1.25 2025/09/14 16:00:04 thorpej Exp $ */
+/* $NetBSD: spivar.h,v 1.26 2025/10/10 18:36:17 brad Exp $ */
 
 /*-
  * Copyright (c) 2006 Urbana-Champaign Independent Media Center.
@@ -46,6 +46,7 @@
 
 #include <sys/device.h>
 #include <sys/queue.h>
+#include <sys/uio.h> /* for iovec */
 
 /*
  * Serial Peripheral Interface bus.  This is a 4-wire bus common for
@@ -192,8 +193,14 @@ void	spi_wait(struct spi_transfer *);
 void	spi_done(struct spi_transfer *, int);
 
 /* convenience wrappers */
+struct spi_chunk_q {
+	struct spi_chunk chunk;
+	SIMPLEQ_ENTRY(spi_chunk_q) chunk_q;
+};
+
 int	spi_send(spi_handle_t, int, const uint8_t *);
 int	spi_recv(spi_handle_t, int, uint8_t *);
 int	spi_send_recv(spi_handle_t, int, const uint8_t *, int, uint8_t *);
+int	spi_sendv(spi_handle_t, const struct iovec *, int);
 
 #endif	/* _DEV_SPI_SPIVAR_H_ */