drivers: analog: adc: add poll support

drivers/analog/Kconfig

@@ -33,6 +33,13 @@ config ADC_FIFOSIZE
 		this is a ring buffer, the actual number of bytes that can be
 		retained in buffer is (ADC_FIFOSIZE - 1).
 
+config ADC_NPOLLWAITERS
+	int "Number of poll waiters"
+	default 2
+	depends on !DISABLE_POLL
+	---help---
+		Maximum number of threads that can be waiting on poll.
+
 config ADC_ADS1242
 	bool "TI ADS1242 support"
 	default n

drivers/analog/adc.c

@@ -75,6 +75,10 @@ static ssize_t adc_read(FAR struct file *fielp, FAR char *buffer,
 static int     adc_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
 static int     adc_receive(FAR struct adc_dev_s *dev, uint8_t ch,
                            int32_t data);
+static void    adc_notify(FAR struct adc_dev_s *dev);
+#ifndef CONFIG_DISABLE_POLL
+static int     adc_poll(FAR struct file *filep, struct pollfd *fds, bool setup);
+#endif
 
 /****************************************************************************
  * Private Data
@@ -89,7 +93,10 @@ static const struct file_operations g_adc_fops =
   0,            /* seek */
   adc_ioctl     /* ioctl */
 #ifndef CONFIG_DISABLE_POLL
-  , 0           /* poll */
+  , adc_poll    /* poll */
+#endif
+#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
+  , NULL        /* unlink */
 #endif
 };
 
@@ -449,10 +456,7 @@ static int adc_receive(FAR struct adc_dev_s *dev, uint8_t ch, int32_t data)
 
       fifo->af_tail = nexttail;
 
-      if (dev->ad_nrxwaiters > 0)
+      adc_notify(dev);
-        {
-          sem_post(&fifo->af_sem);
-        }
 
       errcode = OK;
     }
@@ -460,6 +464,132 @@ static int adc_receive(FAR struct adc_dev_s *dev, uint8_t ch, int32_t data)
   return errcode;
 }
 
+/****************************************************************************
+ * Name: adc_pollnotify
+ ****************************************************************************/
+
+#ifndef CONFIG_DISABLE_POLL
+static void adc_pollnotify(FAR struct adc_dev_s *dev, uint32_t type)
+{
+  int i;
+
+  for (i = 0; i < CONFIG_ADC_NPOLLWAITERS; i++)
+    {
+      struct pollfd *fds = dev->fds[i];
+      if (fds)
+        {
+          fds->revents |= type;
+          sem_post(fds->sem);
+        }
+    }
+}
+#endif
+
+/****************************************************************************
+ * Name: adc_notify
+ ****************************************************************************/
+
+static void adc_notify(FAR struct adc_dev_s *dev)
+{
+  FAR struct adc_fifo_s *fifo = &dev->ad_recv;
+
+  /* If there are threads waiting for read data, then signal one of them
+   * that the read data is available.
+   */
+
+  if (dev->ad_nrxwaiters > 0)
+    {
+      sem_post(&fifo->af_sem);
+    }
+
+  /* If there are threads waiting on poll() for data to become available,
+   * then wake them up now.
+   */
+
+#ifndef CONFIG_DISABLE_POLL
+   adc_pollnotify(dev, POLLIN);
+#endif
+}
+
+/************************************************************************************
+ * Name: adc_poll
+ ************************************************************************************/
+
+#ifndef CONFIG_DISABLE_POLL
+static int adc_poll(FAR struct file *filep, struct pollfd *fds, bool setup)
+{
+  FAR struct inode     *inode = filep->f_inode;
+  FAR struct adc_dev_s *dev   = inode->i_private;
+  irqstate_t flags;
+  int ret = 0;
+  int i;
+
+  /* Interrupts must be disabled while accessing the list of poll structures
+   * and ad_recv FIFO.
+   */
+
+  flags = enter_critical_section();
+
+  if (setup)
+    {
+      /* Ignore waits that do not include POLLIN */
+
+      if ((fds->events & POLLIN) == 0)
+        {
+          ret = -EDEADLK;
+          goto return_with_irqdisabled;
+        }
+
+      /* This is a request to set up the poll.  Find an available
+       * slot for the poll structure reference
+       */
+
+      for (i = 0; i < CONFIG_ADC_NPOLLWAITERS; i++)
+        {
+          /* Find an available slot */
+
+          if (!dev->fds[i])
+            {
+              /* Bind the poll structure and this slot */
+
+              dev->fds[i] = fds;
+              fds->priv   = &dev->fds[i];
+              break;
+            }
+        }
+
+      if (i >= CONFIG_ADC_NPOLLWAITERS)
+        {
+          fds->priv    = NULL;
+          ret          = -EBUSY;
+          goto return_with_irqdisabled;
+        }
+
+      /* Should we immediately notify on any of the requested events? */
+
+      if (dev->ad_recv.af_head != dev->ad_recv.af_tail)
+        {
+          adc_pollnotify(dev, POLLIN);
+        }
+    }
+  else if (fds->priv)
+    {
+      /* This is a request to tear down the poll. */
+
+      struct pollfd **slot = (struct pollfd **)fds->priv;
+
+      /* Remove all memory of the poll setup */
+
+      *slot                = NULL;
+      fds->priv            = NULL;
+    }
+
+return_with_irqdisabled:
+  leave_critical_section(flags);
+  return ret;
+}
+#endif
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/

include/nuttx/analog/adc.h

@@ -50,6 +50,7 @@
 #include <nuttx/config.h>
 #include <nuttx/compiler.h>
 
+#include <poll.h>
 #include <sys/types.h>
 #include <stdint.h>
 #include <stdbool.h>
@@ -72,6 +73,10 @@
 #  define CONFIG_ADC_FIFOSIZE 255
 #endif
 
+#if !defined(CONFIG_ADC_NPOLLWAITERS)
+#  define CONFIG_ADC_NPOLLWAITERS 2
+#endif
+
 #define ADC_RESET(dev)         ((dev)->ad_ops->ao_reset((dev)))
 #define ADC_SETUP(dev)         ((dev)->ad_ops->ao_setup((dev)))
 #define ADC_SHUTDOWN(dev)      ((dev)->ad_ops->ao_shutdown((dev)))
@@ -183,8 +188,18 @@ struct adc_dev_s
   sem_t                       ad_closesem;   /* Locks out new opens while close is in progress */
   sem_t                       ad_recvsem;    /* Used to wakeup user waiting for space in ad_recv.buffer */
   struct adc_fifo_s           ad_recv;       /* Describes receive FIFO */
+
+  /* The following is a list of poll structures of threads waiting for
+   * driver events. The 'struct pollfd' reference for each open is also
+   * retained in the f_priv field of the 'struct file'.
+   */
+
+#if !defined(CONFIG_DISABLE_POLL)
+  struct pollfd *fds[CONFIG_ADC_NPOLLWAITERS];
 #endif
 
+#endif /* CONFIG_ADC */
+
   /* Fields provided by lower half ADC logic */
 
   FAR const struct adc_ops_s *ad_ops;        /* Arch-specific operations */