Implement stubbed-out SPI driver

SPI isn't needed on this platform because we don't need an I/O expander.
So this can be a bunch of stub functions that do nothing. They will be
optimized out during the linking process anyway.

hal/m258ke/spi.c

@@ -0,0 +1,110 @@
+/*
+ * spi.c
+ *
+ *  Created on: Jun 19, 2023
+ *      Author: Doug
+ *
+ * Copyright (C) 2011-2023 Doug Brown
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "../spi.h"
+#include "gpio_hw.h"
+#include <stddef.h>
+
+/** Gets the SPI hardware controller at the specified index
+ *
+ * @param index The index of the controller. No SPI is available on the M258KE.
+ * @return The SPI controller, or NULL if an invalid index is supplied
+ */
+SPIController *SPI_Controller(uint8_t index)
+{
+	(void)index;
+	return NULL;
+}
+
+/** Initializes the supplied SPI controller
+ *
+ * @param c The controller
+ */
+void SPI_InitController(SPIController *c)
+{
+	(void)c;
+}
+
+/** Initializes the supplied SPI device
+ *
+ * @param spi The device
+ * @param maxClock The maximum clock rate supported by the device in Hz
+ * @param mode The SPI mode (see the SPI_MODE_*, SPI_CPHA, and SPI_CPOL defines)
+ * @return True on success, false on failure
+ */
+bool SPI_InitDevice(SPIDevice *spi, uint32_t maxClock, uint8_t mode)
+{
+	(void)spi;
+	(void)maxClock;
+	(void)mode;
+	return false;
+}
+
+/** Allows an SPI device to request control of the bus.
+ *
+ * @param spi The SPI device
+ */
+void SPI_RequestBus(SPIDevice *spi)
+{
+	(void)spi;
+}
+
+/** Allows an SPI device to relinquish control of the bus.
+ *
+ * @param spi The SPI device
+ */
+void SPI_ReleaseBus(SPIDevice *spi)
+{
+	(void)spi;
+}
+
+/** Asserts an SPI device's chip select pin
+ *
+ * @param spi The SPI device
+ */
+void SPI_Assert(SPIDevice *spi)
+{
+	(void)spi;
+}
+
+/** Deasserts an SPI device's chip select pin
+ *
+ * @param spi The SPI device
+ */
+void SPI_Deassert(SPIDevice *spi)
+{
+	(void)spi;
+}
+
+/** Transfers a single byte to/from an SPI device
+ *
+ * @param spi The SPI device
+ * @param b The byte to send
+ * @return The byte that was simultaneously received
+ */
+uint8_t SPI_RWByte(SPIDevice *spi, uint8_t b)
+{
+	(void)spi;
+	(void)b;
+	return 0;
+}

hal/m258ke/spi_private.h

@@ -0,0 +1,33 @@
+/*
+ * spi_private.h
+ *
+ *  Created on: Jun 19, 2023
+ *      Author: Doug
+ *
+ * Copyright (C) 2011-2023 Doug Brown
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef HAL_M258KE_SPI_PRIVATE_H_
+#define HAL_M258KE_SPI_PRIVATE_H_
+
+/// Private data for an SPI device on the M258KE
+typedef struct SPIDevicePrivate
+{
+	/// There's nothing needed. We don't need SPI on this device.
+} SPIDevicePrivate;
+
+#endif /* HAL_M258KE_SPI_PRIVATE_H_ */