[GitHub] [incubator-nuttx] patacongo commented on a change in pull request #2717: I2C bitbang driver (and nRF52 implementation)

[GitBox <gi...@apache.org>]

patacongo commented on a change in pull request #2717:
URL: https://github.com/apache/incubator-nuttx/pull/2717#discussion_r559901483



##########
File path: drivers/i2c/i2c_bitbang.c
##########
@@ -0,0 +1,340 @@
+/****************************************************************************
+ * arch/arm/src/nrf52/nrf52_i2c.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/irq.h>
+#include <nuttx/arch.h>
+#include <nuttx/semaphore.h>
+#include <nuttx/kmalloc.h>
+#include <arch/board/board.h>
+#include <nuttx/i2c/i2c_master.h>
+#include <nuttx/i2c/i2c_bitbang.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct i2c_bitbang_dev_s
+{
+  struct i2c_master_s i2c;
+  struct i2c_bitbang_lower_dev_s *lower;
+
+#ifdef CONFIG_I2C_BITBANG_NO_DELAY
+  uint32_t delay;
+#endif
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int i2c_bitbang_transfer(FAR struct i2c_master_s *dev,
+                                FAR struct i2c_msg_s *msgs, int count);
+
+static int i2c_bitbang_set_scl(FAR struct i2c_bitbang_dev_s *dev,
+                               bool high);
+static void i2c_bitbang_set_sda(FAR struct i2c_bitbang_dev_s *dev,
+                                bool high);
+
+static int i2c_bitbang_wait_ack(FAR struct i2c_bitbang_dev_s *dev);
+static void i2c_bitbang_send(FAR struct i2c_bitbang_dev_s *dev,
+                             uint8_t data);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+struct i2c_ops_s g_i2c_ops =
+{
+  .transfer = i2c_bitbang_transfer
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: i2c_bitbang_transfer
+ ****************************************************************************/
+
+static int i2c_bitbang_transfer(FAR struct i2c_master_s *dev,

Review comment:
       > Right. Is `spin_lock_irqsave` OK? Not entirely sure when to use it instead of `enter_critical_section`.
   
   You can use spin_lock_irqsave() when the thread cannot possibly suspend itself within the critical section.  If you can tolerate jitter from interrupt processing, sched_lock() will keep the thread in place, i.e., that it cannot be suspended.




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