driver/mem:add Mem Driver.

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

Documentation/components/drivers/special/devmem.rst

@@ -0,0 +1,26 @@
+==============
+DEVMEM Drivers
+==============
+
+The `devmem` driver provides an interface for accessing memory-mapped
+I/O in an embedded system. This driver allows for reading, writing, and
+memory mapping of specific memory regions or device registers.
+
+``read()``: This function reads data from the memory-mapped I/O address
+  space into the buffer provided by the caller. The first byte read
+  corresponds to the address specified by the device's "current memory
+  address". The addresses for subsequent bytes depend on the auto-increment
+  behavior of the specific device.
+
+``write()``: This function transfers data from the provided data buffer by
+  the caller to the memory-mapped I/O address space. The first byte written
+  corresponds to the address specified by the device's "current memory address".
+
+``mmap()``: The `mmap()` function provides a mechanism to map a device's
+  memory region into the user space, allowing direct access to device
+  registers or memory regions. The mapped region can be accessed using
+  normal memory operations.
+
+  The function requires a base address and size for the memory region
+  to be mapped. If successful, it returns a pointer to the mapped region.
+  If mapping fails, it returns `EINVAL` and `errno` is set appropriately.

Documentation/components/drivers/special/index.rst

@@ -25,6 +25,7 @@ following section.
   audio.rst
   clk.rst
   devicetree.rst
+  devmem.rst
   dma.rst
   framebuffer.rst
   i2c.rst

drivers/drivers_initialize.c

@@ -129,6 +129,10 @@ void drivers_initialize(void)
   devzero_register();   /* Standard /dev/zero */
 #endif
 
+#ifdef CONFIG_DEV_MEM
+  devmem_register();
+#endif
+
 #if defined(CONFIG_DEV_LOOP)
   loop_register();      /* Standard /dev/loop */
 #endif

drivers/misc/Kconfig

@@ -15,6 +15,13 @@ config DEV_ZERO
 	bool "Enable /dev/zero"
 	default n
 
+config DEV_MEM
+	bool "Enable /dev/mem"
+	default n
+	---help---
+		It is a full image of physical memory and can be used to
+		access physical memory.
+
 config DEV_ASCII
 	bool "Enable /dev/ascii"
 	default n

drivers/misc/Make.defs

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

drivers/misc/dev_mem.c

@@ -0,0 +1,262 @@
+/****************************************************************************
+ * drivers/misc/dev_mem.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/drivers/drivers.h>
+#include <nuttx/kmalloc.h>
+#include <nuttx/memoryregion.h>
+#include <sys/param.h>
+#include <sys/mman.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define DEVMEM_REGION 8
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+extern uint8_t _stext[];           /* Start of .text */
+extern uint8_t _etext[];           /* End_1 of .text + .rodata */
+extern uint8_t _sdata[];           /* Start of .data */
+extern uint8_t _edata[];           /* End+1 of .data */
+extern uint8_t _sbss[];            /* Start of .bss */
+extern uint8_t _ebss[];            /* End+1 of .bss */
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Character driver methods */
+
+static ssize_t devmem_read(FAR struct file *filep, FAR char *buffer,
+                           size_t buflen);
+static ssize_t devmem_write(FAR struct file *filep, FAR const char *buffer,
+                            size_t buflen);
+static int     devmem_mmap(FAR struct file *filep,
+                           FAR struct mm_map_entry_s *map);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_devmem_fops =
+{
+  NULL,                  /* open */
+  NULL,                  /* close */
+  devmem_read,           /* read */
+  devmem_write,          /* write */
+  NULL,                  /* seek */
+  NULL,                  /* ioctl */
+  devmem_mmap,           /* mmap */
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: devmem_read
+ ****************************************************************************/
+
+static ssize_t devmem_read(FAR struct file *filep, FAR char *buffer,
+                           size_t buflen)
+{
+  FAR struct memory_region_s *region = filep->f_inode->i_private;
+  uintptr_t src = filep->f_pos;
+  uintptr_t start;
+  uintptr_t end;
+  ssize_t len;
+  int i;
+
+  DEBUGASSERT(region && src);
+
+  for (i = 0; i < DEVMEM_REGION; i++)
+    {
+      if (region[i].start == 0 && region[i].end == 0)
+        {
+          break;
+        }
+
+      start = MAX(src, region[i].start);
+      end = MIN(src + buflen, region[i].end);
+      len = end - start;
+      if (len > 0 && (region[i].flags & PROT_READ))
+        {
+          memcpy(buffer, (FAR const void *)start, len);
+          return len;
+        }
+    }
+
+  return -EINVAL;
+}
+
+/****************************************************************************
+ * Name: devmem_write
+ ****************************************************************************/
+
+static ssize_t devmem_write(FAR struct file *filep, FAR const char *buffer,
+                            size_t buflen)
+{
+  FAR struct memory_region_s *region = filep->f_inode->i_private;
+  uintptr_t dest = filep->f_pos;
+  uintptr_t start;
+  uintptr_t end;
+  ssize_t len;
+  int i;
+
+  DEBUGASSERT(region && dest);
+
+  for (i = 0; i < DEVMEM_REGION; i++)
+    {
+      if (region[i].start == 0 && region[i].end == 0)
+        {
+          break;
+        }
+
+      start = MAX(dest, region[i].start);
+      end = MIN(dest + buflen, region[i].end);
+      len = end - start;
+      if (len > 0 && (region[i].flags & PROT_WRITE))
+        {
+          memcpy((FAR void *)start, buffer, len);
+          return len;
+        }
+    }
+
+  return -EINVAL;
+}
+
+/****************************************************************************
+ * Name: devmem_mmap
+ ****************************************************************************/
+
+static int devmem_mmap(FAR struct file *filep,
+                       FAR struct mm_map_entry_s *map)
+{
+  FAR struct memory_region_s *region = filep->f_inode->i_private;
+  uintptr_t start;
+  uintptr_t end;
+  int i;
+
+  DEBUGASSERT(region);
+
+  if (map->offset < 0)
+    {
+      return -EINVAL;
+    }
+
+  start = map->offset;
+  end = start + map->length;
+
+  for (i = 0; i < DEVMEM_REGION; i++)
+    {
+      if (region[i].start == 0 && region[i].end == 0)
+        {
+          break;
+        }
+
+      if (start >= region[i].start && end <= region[i].end)
+        {
+          map->vaddr = (FAR void *)start;
+          return 0;
+        }
+    }
+
+  return -EINVAL;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: devmem_register
+ *
+ * Description:
+ *   Create an MEM driver.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; A negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int devmem_register(void)
+{
+  FAR struct memory_region_s *region;
+  bool merge = (_edata == _sbss);
+  ssize_t len = 0;
+  int ret;
+
+  region = kmm_calloc(DEVMEM_REGION, sizeof(*region));
+  if (region == NULL)
+    {
+      return -ENOMEM;
+    }
+
+#ifdef CONFIG_BOARD_MEMORY_RANGE
+  len = parse_memory_region(CONFIG_BOARD_MEMORY_RANGE, region,
+                            DEVMEM_REGION - 1);
+  if (len < 0)
+    {
+      kmm_free(region);
+      return len;
+    }
+#endif
+
+  if (len + (4 - merge) > DEVMEM_REGION)
+    {
+      len = DEVMEM_REGION - (4 - merge);
+    }
+
+  region[len].flags = PROT_EXEC | PROT_READ;
+  region[len].start = (uintptr_t)_stext;
+  region[len++].end = (uintptr_t)_etext;
+  region[len].flags = PROT_WRITE | PROT_READ;
+  region[len].start = (uintptr_t)_sdata;
+  region[len++].end = (uintptr_t)_edata;
+
+  if (merge)
+    {
+      region[len - 1].end = (uintptr_t)_ebss;
+    }
+  else
+    {
+      region[len].flags = PROT_WRITE | PROT_READ;
+      region[len].start = (uintptr_t)_sbss;
+      region[len++].end = (uintptr_t)_ebss;
+    }
+
+  /* register the new MEM driver */
+
+  ret = register_driver("/dev/mem", &g_devmem_fops, 0666, region);
+  if (ret < 0)
+    {
+      kmm_free(region);
+      return -ENOMEM;
+    }
+
+  return ret;
+}

include/nuttx/drivers/drivers.h

@@ -144,6 +144,18 @@ void devurandom_register(void);
 
 void devcrypto_register(void);
 
+/****************************************************************************
+ * Name: devmem_register
+ *
+ * Description:
+ *   Register devmem driver
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_DEV_MEM
+int devmem_register(void);
+#endif
+
 /****************************************************************************
  * Name: devzero_register
  *