drivers/spi: Add a helper function that encapsulates and manages a sequency of SPI transfers.

include/nuttx/spi/spi.h

@@ -140,7 +140,8 @@
  *   csdelay    - The delay between CS inactive and CS active again
  *
  * Returned Value:
- *   Returns the actual frequency selected
+ *   Returns zero (OK) on success; a negated errno value is return on any
+ *   failure.
  *
  ****************************************************************************/
 

include/nuttx/spi/spi_transfer.h

@@ -0,0 +1,147 @@
+/****************************************************************************
+ * include/nuttx/spi/spi_transfer.h
+ *
+ *   Copyright(C) 2015-2016 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES(INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_SPI_TRANSFER_H
+#define __INCLUDE_NUTTX_SPI_TRANSFER_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include <nuttx/spi/spi.h>
+
+#ifdef CONFIG_SPI_EXCHANGE
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/* This describes one SPI transaction as handled by spi_transfer() */
+
+struct spi_trans_s
+{
+  /* SPI attributes for unique to this transaction */
+
+#ifdef CONFIG_SPI_CMDDATA
+  bool cmd;                 /* true=command; false=data */
+#endif
+#ifdef CONFIG_SPI_HWFEATURES
+  spi_hwfeatures_t hwfeat;  /* Hard features to enable on this transfer */
+#endif
+
+  /* These describe the single data transfer */
+
+  size_t nwords;            /* Number of words in transfer */
+  FAR const void *txbuffer; /* Source buffer for TX transfer */
+  FAR void *rxbuffer;       /* Sink buffer for RX transfer */
+};
+
+/* This describes a sequence of SPI transactions as handled by spi_transfer.
+ *
+ * Example usage:
+ *   struct spi_trans_s mytrans[5];
+ *   struct spi_sequence_s myseq;
+ *   ...
+ *   myseq.ntrans = 5;
+ *   myseq.trans  = mytrans;
+ *   ...
+ *   int ret = spi_transfer(spi, myseq);
+ *   ...
+ */
+
+struct spi_sequence_s
+{
+  /* Properties that are fixed throughout the transfer */
+
+  uint8_t dev;                 /* See enum spi_dev_e */
+  uint8_t mode;                /* See enum spi_mode_e */
+  uint8_t nbits;               /* Number of bits */
+  uint8_t ntrans;              /* Number of transactions */
+  uint32_t frequency;          /* SPI frequency (Hz) */
+#ifdef CONFIG_SPI_CS_DELAY_CONTROL
+  uint32_t a;                  /* Arguments to setdelay() */
+  uint32_t b;
+  uint32_t c;
+#endif
+
+  /* A pointer to the list of transfers to be be performed. */
+
+  FAR struct spi_trans_s *trans;
+};
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: spi_transfer
+ *
+ * Description:
+ *   This is a helper function that can be used to encapsulate and manage
+ *   a sequence of SPI transfers.
+ *
+ * Input Parameters:
+ *   spi - An instance of the SPI device to use for the transfer
+ *   seq - Describes the sequence of transfers.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int spi_transfer(FAR struct spi_dev_s *spi, FAR struct spi_sequence_s *seq);
+
+#undef EXTERN
+#if defined(__cplusplus)
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+#undef EXTERN
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* CONFIG_SPI_EXCHANGE */
+#endif /* __INCLUDE_NUTTX_SPI_TRANSFER_H */