drivers: add ascii drvier, returns a printable string of 0x21-0x7f

Signed-off-by: yinshengkai <yinshengkai@xiaomi.com>

drivers/drivers_initialize.c

@@ -92,6 +92,10 @@ void drivers_initialize(void)
   loop_register();      /* Standard /dev/loop */
 #endif
 
+#if defined(CONFIG_DEV_ASCII)
+  devascii_register();  /* Non-standard /dev/ascii */
+#endif
+
 #if defined(CONFIG_DRIVERS_NOTE)
   note_initialize();    /* Non-standard /dev/note */
 #endif

drivers/misc/Kconfig

@@ -15,6 +15,13 @@ config DEV_ZERO
 	bool "Enable /dev/zero"
 	default n
 
+config DEV_ASCII
+	bool "Enable /dev/ascii"
+	default n
+	---help---
+		Enable the /dev/ascii device driver.  This is a character driver
+		that will return all characters from 0x21-0x7f.
+
 config DEV_RPMSG
 	bool "RPMSG Device Client Support"
 	default n

drivers/misc/Make.defs

@@ -30,6 +30,10 @@ ifeq ($(CONFIG_DEV_ZERO),y)
   CSRCS += dev_zero.c
 endif
 
+ifeq ($(CONFIG_DEV_ASCII),y)
+  CSRCS += dev_ascii.c
+endif
+
 ifeq ($(CONFIG_LWL_CONSOLE),y)
   CSRCS += lwl_console.c
 endif

drivers/misc/dev_ascii.c

@@ -0,0 +1,139 @@
+/****************************************************************************
+ * drivers/misc/dev_ascii.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 <sys/types.h>
+#include <poll.h>
+
+#include <nuttx/fs/fs.h>
+#include <nuttx/drivers/drivers.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define PRINTABLE_FIRST 0x20
+#define PRINTABLE_COUNT (0x7f - 0x20)
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static ssize_t devascii_read(FAR struct file *filep, FAR char *buffer,
+                             size_t buflen);
+static ssize_t devascii_write(FAR struct file *filep, FAR const char *buffer,
+                              size_t buflen);
+static int devascii_poll(FAR struct file *filep, FAR struct pollfd *fds,
+                         bool setup);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_devascii_fops =
+{
+  NULL,           /* open */
+  NULL,           /* close */
+  devascii_read,  /* read */
+  devascii_write, /* write */
+  NULL,           /* seek */
+  NULL,           /* ioctl */
+  NULL,           /* mmap */
+  NULL,           /* truncate */
+  devascii_poll   /* poll */
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: devascii_read
+ ****************************************************************************/
+
+static ssize_t devascii_read(FAR struct file *filep, FAR char *buffer,
+                             size_t len)
+{
+  size_t i;
+  for (i = 0; i < len; i++)
+    {
+      buffer[i] = PRINTABLE_FIRST + (filep->f_pos + i) % PRINTABLE_COUNT;
+
+      /* Replace the space character with a newline */
+
+      if (buffer[i] == PRINTABLE_FIRST)
+        {
+          buffer[i] = '\n';
+        }
+    }
+
+  filep->f_pos += len;
+  return len;
+}
+
+/****************************************************************************
+ * Name: devascii_write
+ ****************************************************************************/
+
+static ssize_t devascii_write(FAR struct file *filep, FAR const char *buffer,
+                              size_t len)
+{
+  UNUSED(filep);
+  UNUSED(buffer);
+
+  return len;
+}
+
+/****************************************************************************
+ * Name: devascii_poll
+ ****************************************************************************/
+
+static int devascii_poll(FAR struct file *filep, FAR struct pollfd *fds,
+                         bool setup)
+{
+  UNUSED(filep);
+
+  if (setup)
+    {
+      poll_notify(&fds, 1, POLLIN | POLLOUT);
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: devascii_register
+ *
+ * Description:
+ *   Register /dev/ascii
+ *
+ ****************************************************************************/
+
+void devascii_register(void)
+{
+  register_driver("/dev/ascii", &g_devascii_fops, 0666, NULL);
+}