rtio: SPI support

drivers/spi/CMakeLists.txt

@@ -37,5 +37,6 @@ zephyr_library_sources_ifdef(CONFIG_NXP_S32_SPI spi_nxp_s32.c)
 zephyr_library_sources_ifdef(CONFIG_SPI_XMC4XXX     spi_xmc4xxx.c)
 zephyr_library_sources_ifdef(CONFIG_SPI_PW		spi_pw.c)
 
+zephyr_library_sources_ifdef(CONFIG_SPI_RTIO spi_rtio.c)
 zephyr_library_sources_ifdef(CONFIG_SPI_ASYNC spi_signal.c)
 zephyr_library_sources_ifdef(CONFIG_USERSPACE		spi_handlers.c)

drivers/spi/Kconfig

@@ -19,6 +19,14 @@ config SPI_ASYNC
 	help
 	  This option enables the asynchronous API calls.
 
+config SPI_RTIO
+	bool "RTIO support [EXPERIMENTAL]"
+	select EXPERIMENTAL
+	select RTIO
+	help
+	  This option enables the RTIO API calls. RTIO support is
+	  experimental as the API itself is unstable.
+
 config SPI_SLAVE
 	bool "Slave support [EXPERIMENTAL]"
 	select EXPERIMENTAL

drivers/spi/Kconfig.sam

@@ -19,4 +19,19 @@ config SPI_SAM_DMA
 	help
 	  Enable using DMA with SPI for SPI instances that enable dma channels in
 	  their device tree node.
+
+if SPI_RTIO
+config SPI_SAM_RTIO_SQ_SIZE
+	int "Number of avialable submission queue entries"
+	default 8 # Sensible default that covers most common spi transactions
+	help
+	  When RTIO is use with SPI each driver holds a context with which blocking
+	  API calls use to perform SPI transactions. This queue needs to be as deep
+	  as the longest set of spi_buf_sets used, where normal SPI operations are
+	  used (equal length buffers). It may need to be slightly deeper where the
+	  spi buffer sets for transmit/receive are not always matched equally in
+	  length as these are transformed into normal transceives.
+
+endif # SPI_RTIO
+
 endif # SPI_SAM

drivers/spi/spi_rtio.c

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2023 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/spi.h>
+
+const struct rtio_iodev_api spi_iodev_api = {
+	.submit = spi_iodev_submit,
+};