syslog/ramlog: get ramlog size by ioctl

Signed-off-by: Jiuzhu Dong <dongjiuzhu1@xiaomi.com>

drivers/syslog/ramlog.c

@@ -43,6 +43,7 @@
 #include <nuttx/kmalloc.h>
 #include <nuttx/semaphore.h>
 #include <nuttx/fs/fs.h>
+#include <nuttx/fs/ioctl.h>
 #include <nuttx/syslog/ramlog.h>
 #include <nuttx/compiler.h>
 
@@ -57,16 +58,16 @@
 struct ramlog_dev_s
 {
 #ifndef CONFIG_RAMLOG_NONBLOCKING
-  volatile uint8_t  rl_nwaiters;     /* Number of threads waiting for data */
+  volatile uint8_t  rl_nwaiters; /* Number of threads waiting for data */
 #endif
-  volatile uint16_t rl_head;         /* The head index (where data is added) */
-  volatile uint16_t rl_tail;         /* The tail index (where data is removed) */
-  sem_t             rl_exclsem;      /* Enforces mutually exclusive access */
+  volatile size_t   rl_head;     /* The head index (where data is added) */
+  volatile size_t   rl_tail;     /* The tail index (where data is removed) */
+  sem_t             rl_exclsem;  /* Enforces mutually exclusive access */
 #ifndef CONFIG_RAMLOG_NONBLOCKING
-  sem_t             rl_waitsem;      /* Used to wait for data */
+  sem_t             rl_waitsem;  /* Used to wait for data */
 #endif
-  size_t            rl_bufsize;      /* Size of the RAM buffer */
-  FAR char         *rl_buffer;       /* Circular RAM buffer */
+  size_t            rl_bufsize;  /* Size of the RAM buffer */
+  FAR char         *rl_buffer;   /* Circular RAM buffer */
 
   /* The following is a list if poll structures of threads waiting for
    * driver events. The 'struct pollfd' reference for each open is also
@@ -95,6 +96,8 @@ static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer,
                            size_t buflen);
 static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer,
                             size_t buflen);
+static int     ramlog_ioctl(FAR struct file *filep, int cmd,
+                            unsigned long arg);
 static int     ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds,
                            bool setup);
 
@@ -109,7 +112,7 @@ static const struct file_operations g_ramlogfops =
   ramlog_read,  /* read */
   ramlog_write, /* write */
   NULL,         /* seek */
-  NULL,         /* ioctl */
+  ramlog_ioctl, /* ioctl */
   ramlog_poll   /* poll */
 #ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
   , NULL        /* unlink */
@@ -534,11 +537,47 @@ static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer,
   return len;
 }
 
+/****************************************************************************
+ * Name: ramlog_ioctl
+ ****************************************************************************/
+
+static int ramlog_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
+{
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct ramlog_dev_s *priv;
+  int ret;
+
+  DEBUGASSERT(inode && inode->i_private);
+  priv = (FAR struct ramlog_dev_s *)inode->i_private;
+
+  ret = nxsem_wait(&priv->rl_exclsem);
+  if (ret < 0)
+    {
+      return ret;
+    }
+
+  switch (cmd)
+    {
+      case FIONREAD:
+        *(FAR int *)((uintptr_t)arg) = (priv->rl_bufsize + priv->rl_head -
+                                        priv->rl_tail) % priv->rl_bufsize;
+        break;
+      default:
+        ret = -ENOTTY;
+        break;
+    }
+
+  nxsem_post(&priv->rl_exclsem);
+
+  return ret;
+}
+
 /****************************************************************************
  * Name: ramlog_poll
  ****************************************************************************/
 
-int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
+static int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds,
+                       bool setup)
 {
   FAR struct inode *inode = filep->f_inode;
   FAR struct ramlog_dev_s *priv;