drivers/spi: Add SPI Slave character device driver

drivers/spi/Kconfig

@@ -26,21 +26,81 @@ menuconfig SPI
 if SPI
 
 config SPI_SLAVE
-	bool "SPI slave"
+	bool "SPI Slave"
 	default n
 	---help---
-		Enable support for SPI slave features
+		Enable support for SPI Slave features
 
 if SPI_SLAVE
 
+config SPI_SLAVE_DRIVER
+	bool "SPI Slave character driver"
+	default n
+	---help---
+		Built-in support for a character driver at /dev/spislv[N] that may be
+		used to perform SPI bus transfers from applications.
+		The intent of this driver is to support SPI Slave testing.
+
+if SPI_SLAVE_DRIVER
+
+config SPI_SLAVE_DRIVER_MODE
+	int "SPI Slave character driver default mode"
+	default 0
+	---help---
+		Default SPI Slave character driver mode, where:
+		0 = CPOL=0, CPHA=0
+		1 = CPOL=0, CPHA=1
+		2 = CPOL=1, CPHA=0
+		3 = CPOL=1, CPHA=1
+
+config SPI_SLAVE_DRIVER_WIDTH
+	int "SPI Slave character driver default bit width"
+	default 8
+	---help---
+		Number of bits per SPI Slave transfer (default 8).
+
+config SPI_SLAVE_DRIVER_BUFFER_SIZE
+	int "SPI Slave character driver TX and RX buffer sizes"
+	default 128
+	---help---
+		Size of the internal TX and RX buffers of the SPI Slave
+		character driver.
+
+config SPI_SLAVE_DRIVER_COLORIZE_TX_BUFFER
+	bool "SPI Slave character driver colorize TX buffer"
+	default n
+	---help---
+		Initialize entries of the TX buffer with a given pattern.
+		If the SPI Slave controller performs a call to "getdata" API during
+		the "bind" operation, the colorized buffer may be sent as part of the
+		first TX transfer of the SPI Slave controller.
+		This feature might be useful for a quick communication test between
+		Master and Slave.
+
+config SPI_SLAVE_DRIVER_COLORIZE_PATTERN
+	hex "SPI Slave character driver colorize pattern"
+	default 0xa5
+	depends on SPI_SLAVE_DRIVER_COLORIZE_TX_BUFFER
+	---help---
+		Pattern to be used as the coloration of the TX buffer.
+
+config SPI_SLAVE_DRIVER_COLORIZE_NUM_BYTES
+	int "SPI Slave character driver colorize number of bytes"
+	default 4
+	depends on SPI_SLAVE_DRIVER_COLORIZE_TX_BUFFER
+	---help---
+		Number of bytes of the TX buffer to be colorized.
+
+endif # SPI_SLAVE_DRIVER
+
 config SPI_SLAVE_DMA
-	bool "SPI slave DMA"
+	bool "SPI Slave DMA"
 	default n
 	depends on ARCH_DMA && EXPERIMENTAL
 	---help---
 		Enable support for DMA data transfers (not yet implemented).
 
-endif
+endif # SPI_SLAVE
 
 config SPI_EXCHANGE
 	bool "SPI exchange"

drivers/spi/Make.defs

@@ -29,6 +29,10 @@ ifeq ($(CONFIG_SPI_EXCHANGE),y)
   endif
 endif
 
+ifeq ($(CONFIG_SPI_SLAVE_DRIVER),y)
+  CSRCS += spi_slave_driver.c
+endif
+
 # Include the selected SPI drivers
 
 ifeq ($(CONFIG_SPI_BITBANG),y)

include/nuttx/spi/slave.h

@@ -534,6 +534,36 @@ struct spi_sdev_s
  * Public Data
  ****************************************************************************/
 
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: spislv_register
+ *
+ * Description:
+ *   Register the SPI Slave echo character device as 'devpath'.
+ *
+ * Input Parameters:
+ *   sctrlr  - An instance of the SPI Slave interface to use to communicate
+ *             with the SPI Slave echo device
+ *   bus     - The SPI Slave bus number. This will be used as the SPI device
+ *             minor number. The SPI Slave character device will be
+ *             registered as /dev/spislvN where N is the minor number
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SPI_SLAVE_DRIVER
+int spislv_register(FAR struct spi_sctrlr_s *sctrlr, int bus);
+#endif /* CONFIG_SPI_SLAVE_DRIVER */
+
 #undef EXTERN
 #if defined(__cplusplus)
 #define EXTERN extern "C"
@@ -547,4 +577,5 @@ extern "C"
 #if defined(__cplusplus)
 }
 #endif
+
 #endif /* __INCLUDE_NUTTX_SPI_SLAVE_H */