[GitHub] [incubator-nuttx] xiaoxiang781216 commented on a diff in pull request #6525: drivers: add support of pwm capture driver

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

xiaoxiang781216 commented on code in PR #6525:
URL: https://github.com/apache/incubator-nuttx/pull/6525#discussion_r906840369


##########
drivers/timers/capture.c:
##########
@@ -0,0 +1,377 @@
+/****************************************************************************
+ * drivers/timers/capture.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 <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fs/fs.h>
+#include <nuttx/arch.h>
+#include <nuttx/semaphore.h>
+#include <nuttx/timers/capture.h>
+
+#include <arch/irq.h>
+
+#ifdef CONFIG_CAPTURE
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Debug ********************************************************************/
+
+/****************************************************************************
+ * Private Type Definitions
+ ****************************************************************************/
+
+/* This structure describes the state of the upper half driver */
+
+struct cap_upperhalf_s
+{
+  uint8_t                    crefs;    /* The number of times the device has been opened */
+  sem_t                      exclsem;  /* Supports mutual exclusion */
+  FAR struct cap_lowerhalf_s *lower;   /* lower-half state */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int     cap_open(FAR struct file *filep);
+static int     cap_close(FAR struct file *filep);
+static ssize_t cap_read(FAR struct file *filep, FAR char *buffer,
+                       size_t buflen);
+static ssize_t cap_write(FAR struct file *filep, FAR const char *buffer,
+                        size_t buflen);
+static int cap_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_capops =
+{
+  cap_open,  /* open */
+  cap_close, /* close */
+  cap_read,  /* read */
+  cap_write, /* write */
+  NULL,      /* seek */
+  cap_ioctl, /* ioctl */
+  NULL,      /* poll */
+#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
+  NULL       /* unlink */
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: cap_open
+ *
+ * Description:
+ *   This function is called whenever the PWM Capture device is opened.
+ *
+ ****************************************************************************/
+
+static int cap_open(FAR struct file *filep)
+{
+  FAR struct inode           *inode = filep->f_inode;
+  FAR struct cap_upperhalf_s *upper = inode->i_private;
+  uint8_t                     tmp;
+  int                         ret;
+
+  /* Get exclusive access to the device structures */
+
+  ret = nxsem_wait(&upper->exclsem);
+  if (ret < 0)
+    {
+      goto errout;
+    }
+
+  /* Increment the count of references to the device.  If this is the first
+   * time that the driver has been opened for this device, then initialize
+   * the device.
+   */
+
+  tmp = upper->crefs + 1;
+  if (tmp == 0)
+    {
+      /* More than 255 opens; uint8_t overflows to zero */
+
+      ret = -EMFILE;
+      goto errout_with_sem;
+    }
+
+  /* Check if this is the first time that the driver has been opened. */
+
+  if (tmp == 1)
+    {
+      FAR struct cap_lowerhalf_s *lower = upper->lower;
+
+      /* Yes.. perform one time hardware initialization. */
+
+      DEBUGASSERT(lower->ops->start != NULL);
+
+      ret = lower->ops->start(lower);

Review Comment:
   should we let user control start/stop the capture through ioctl? so the user don't need open/close the same device multiple times.



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