fdt: Add initial FDT support and procfs for userspace export

VELAPLATFO-12536

This provides the initial hooks for Flattened Device Tree support
with QEMU RV. It also provides a new procfs file that exposes the
fdt to userspace much like the /sys/firmware/fdt endpoint in Linux.
See https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-firmware-ofw

Nodes in the fdt are not yet usable by the OS.

Signed-off-by: Brennan Ashton <bashton@brennanashton.com>
Signed-off-by: liaoao <liaoao@xiaomi.com>

arch/risc-v/src/qemu-rv/qemu_rv_head.S

@@ -41,6 +41,7 @@
 
 __start:
 
+  /* Preserve a1 as it contains the pointer to DTB */
   /* Load mhartid (cpuid) */
 
   csrr a0, mhartid

arch/risc-v/src/qemu-rv/qemu_rv_start.c

@@ -36,6 +36,10 @@
 #  include "qemu_rv_mm_init.h"
 #endif
 
+#ifdef CONFIG_DEVICE_TREE
+#  include <nuttx/fdt.h>
+#endif
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -97,9 +101,9 @@ uintptr_t g_idle_topstack = QEMU_RV_IDLESTACK_TOP;
  ****************************************************************************/
 
 #ifdef CONFIG_BUILD_KERNEL
-void qemu_rv_start_s(int mhartid)
+void qemu_rv_start_s(int mhartid, const char *dtb)
 #else
-void qemu_rv_start(int mhartid)
+void qemu_rv_start(int mhartid, const char *dtb)
 #endif
 {
   /* Configure FPU */
@@ -115,6 +119,10 @@ void qemu_rv_start(int mhartid)
   qemu_rv_clear_bss();
 #endif
 
+#ifdef CONFIG_DEVICE_TREE
+  fdt_register(dtb);
+#endif
+
   showprogress('A');
 
 #ifdef USE_EARLYSERIALINIT
@@ -155,7 +163,7 @@ cpux:
  * Name: qemu_rv_start
  ****************************************************************************/
 
-void qemu_rv_start(int mhartid)
+void qemu_rv_start(int mhartid, const char *dtb)
 {
   /* NOTE: still in M-mode */
 
@@ -209,12 +217,13 @@ void qemu_rv_start(int mhartid)
 
   WRITE_CSR(mepc, (uintptr_t)qemu_rv_start_s);
 
-  /* Set a0 to mhartid explicitly and enter to S-mode */
+  /* Set a0 to mhartid and a1 to dtb explicitly and enter to S-mode */
 
   asm volatile (
       "mv a0, %0 \n"
+      "mv a1, %1 \n"
       "mret \n"
-      :: "r" (mhartid)
+      :: "r" (mhartid), "r" (dtb)
   );
 }
 #endif

boards/risc-v/qemu-rv/rv-virt/configs/nsh64/defconfig

@@ -31,6 +31,7 @@ CONFIG_BOARD_LOOPSPERMSEC=6366
 CONFIG_BUILTIN=y
 CONFIG_DEBUG_FULLOPT=y
 CONFIG_DEBUG_SYMBOLS=y
+CONFIG_DEVICE_TREE=y
 CONFIG_DEV_ZERO=y
 CONFIG_ELF=y
 CONFIG_EXAMPLES_HELLO=m

drivers/Kconfig

@@ -54,3 +54,4 @@ source "drivers/math/Kconfig"
 source "drivers/segger/Kconfig"
 source "drivers/usrsock/Kconfig"
 source "drivers/dma/Kconfig"
+source "drivers/devicetree/Kconfig"

drivers/Makefile

@@ -32,6 +32,7 @@ include bch/Make.defs
 include can/Make.defs
 include clk/Make.defs
 include crypto/Make.defs
+include devicetree/Make.defs
 include dma/Make.defs
 include math/Make.defs
 include motor/Make.defs

drivers/devicetree/CMakeLists.txt

@@ -0,0 +1,24 @@
+# ##############################################################################
+# drivers/devicetree/CMakeLists.txt
+#
+# 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.
+#
+# ##############################################################################
+if(CONFIG_DEVICE_TREE)
+  set(SRCS fdt.c)
+
+  target_sources(drivers PRIVATE ${SRCS})
+endif()

drivers/devicetree/Kconfig

@@ -0,0 +1,10 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+menuconfig DEVICE_TREE
+	bool "Device Tree Support"
+	default n
+	---help---
+		Interface for interacting with devicetree.

drivers/devicetree/Make.defs

@@ -0,0 +1,28 @@
+############################################################################
+# drivers/devicetree/Make.defs
+#
+# 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.
+#
+############################################################################
+
+ifeq ($(CONFIG_DEVICE_TREE),y)
+
+CSRCS += fdt.c
+
+DEPPATH += --dep-path devicetree
+VPATH += :devicetree
+
+endif

drivers/devicetree/fdt.c

@@ -0,0 +1,86 @@
+/****************************************************************************
+ * drivers/devicetree/fdt.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 <stddef.h>
+#include <endian.h>
+#include <errno.h>
+#include <assert.h>
+#include <nuttx/compiler.h>
+#include <nuttx/fdt.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/* Location of the fdt data for this system. */
+
+static FAR const char *g_fdt_base = NULL;
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: fdt_register
+ *
+ * Description:
+ *   Store the pointer to the flattened device tree and verify that it at
+ *   least appears to be valid. This function will not fully parse the FDT.
+ *
+ * Return:
+ *   Return -EINVAL if the fdt header does not have the expected magic value.
+ *   otherwise return OK. If OK is not returned the existing entry for FDT
+ *   is not modified.
+ *
+ ****************************************************************************/
+
+int fdt_register(FAR const char *fdt_base)
+{
+  struct fdt_header_s *fdt_header;
+
+  DEBUGASSERT(fdt_base);
+
+  fdt_header = (struct fdt_header_s *)fdt_base;
+  if (fdt_header->magic != be32toh(FDT_MAGIC))
+    {
+      return -EINVAL; /* Bad magic byte read */
+    }
+
+  g_fdt_base = fdt_base;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: fdt_get
+ *
+ * Description:
+ *   Return the pointer to a raw FDT. NULL is returned if no FDT has been
+ *   loaded.
+ *
+ ****************************************************************************/
+
+FAR const char *fdt_get(void)
+{
+  return g_fdt_base;
+}

fs/procfs/Kconfig

@@ -56,6 +56,14 @@ config FS_PROCFS_EXCLUDE_ENVIRON
 		Causes the environment variable information to be excluded from the
 		procfs system.  This will reduce code space slightly.
 
+config FS_PROCFS_EXCLUDE_FDT
+	bool "Exclude flattened device tree blob"
+	depends on DEVICE_TREE
+	default DEFAULT_SMALL
+	---help---
+		Causes the flatted device tree information to be excluded from the
+		procfs system.  This will reduce code space slightly.
+
 config FS_PROCFS_EXCLUDE_IOBINFO
 	bool "Exclude iobinfo"
 	depends on MM_IOB

fs/procfs/Make.defs

@@ -22,9 +22,9 @@ ifeq ($(CONFIG_FS_PROCFS),y)
 # Files required for procfs file system support
 
 CSRCS += fs_procfs.c fs_procfscpuinfo.c fs_procfscpuload.c
-CSRCS += fs_procfscritmon.c fs_procfsiobinfo.c fs_procfsmeminfo.c
-CSRCS += fs_procfsproc.c fs_procfstcbinfo.c fs_procfsuptime.c
-CSRCS += fs_procfsutil.c fs_procfsversion.c
+CSRCS += fs_procfscritmon.c fs_procfsfdt.c fs_procfsiobinfo.c
+CSRCS += fs_procfsmeminfo.c fs_procfsproc.c fs_procfstcbinfo.c
+CSRCS += fs_procfsuptime.c fs_procfsutil.c fs_procfsversion.c
 
 # Include procfs build support
 

fs/procfs/fs_procfs.c

@@ -55,6 +55,7 @@
 extern const struct procfs_operations g_cpuinfo_operations;
 extern const struct procfs_operations g_cpuload_operations;
 extern const struct procfs_operations g_critmon_operations;
+extern const struct procfs_operations g_fdt_operations;
 extern const struct procfs_operations g_iobinfo_operations;
 extern const struct procfs_operations g_irq_operations;
 extern const struct procfs_operations g_meminfo_operations;
@@ -108,6 +109,10 @@ static const struct procfs_entry_s g_procfs_entries[] =
   { "critmon",      &g_critmon_operations,  PROCFS_FILE_TYPE   },
 #endif
 
+#if defined(CONFIG_DEVICE_TREE) && !defined(CONFIG_FS_PROCFS_EXCLUDE_FDT)
+  { "fdt",          &g_fdt_operations,      PROCFS_FILE_TYPE   },
+#endif
+
 #ifndef CONFIG_FS_PROCFS_EXCLUDE_BLOCKS
   { "fs/blocks",    &g_mount_operations,    PROCFS_FILE_TYPE   },
 #endif

fs/procfs/fs_procfsfdt.c

@@ -0,0 +1,258 @@
+/****************************************************************************
+ * fs/procfs/fs_procfsfdt.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 <sys/stat.h>
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+#include <endian.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fdt.h>
+#include <nuttx/fs/fs.h>
+#include <nuttx/fs/procfs.h>
+
+#if defined(CONFIG_DEVICE_TREE) && !defined(CONFIG_FS_PROCFS_EXCLUDE_FDT)
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/* This structure describes one open "file" */
+
+struct fdt_file_s
+{
+  struct procfs_file_s base;        /* Base open file structure */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* File system methods */
+
+static int     fdt_open(FAR struct file *filep, FAR const char *relpath,
+                        int oflags, mode_t mode);
+static int     fdt_close(FAR struct file *filep);
+static ssize_t fdt_read(FAR struct file *filep, FAR char *buffer,
+                        size_t buflen);
+static int     fdt_dup(FAR const struct file *oldp,
+                       FAR struct file *newp);
+static int     fdt_stat(FAR const char *relpath, FAR struct stat *buf);
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/* See fs_mount.c -- this structure is explicitly externed there.
+ * We use the old-fashioned kind of initializers so that this will compile
+ * with any compiler.
+ */
+
+const struct procfs_operations g_fdt_operations =
+{
+  fdt_open,       /* open */
+  fdt_close,      /* close */
+  fdt_read,       /* read */
+  NULL,           /* write */
+  fdt_dup,        /* dup */
+  NULL,           /* opendir */
+  NULL,           /* closedir */
+  NULL,           /* readdir */
+  NULL,           /* rewinddir */
+  fdt_stat        /* stat */
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: fdt_open
+ ****************************************************************************/
+
+static int fdt_open(FAR struct file *filep, FAR const char *relpath,
+                    int oflags, mode_t mode)
+{
+  FAR struct fdt_file_s *attr;
+
+  finfo("Open '%s'\n", relpath);
+
+  /* PROCFS is read-only.  Any attempt to open with any kind of write
+   * access is not permitted.
+   *
+   * REVISIT:  Write-able proc files could be quite useful.
+   */
+
+  if ((oflags & O_WRONLY) != 0 || (oflags & O_RDONLY) == 0)
+    {
+      ferr("ERROR: Only O_RDONLY supported\n");
+      return -EACCES;
+    }
+
+  /* Allocate a container to hold the file attributes */
+
+  attr = kmm_zalloc(sizeof(struct fdt_file_s));
+  if (attr == NULL)
+    {
+      ferr("ERROR: Failed to allocate file attributes\n");
+      return -ENOMEM;
+    }
+
+  /* Save the attributes as the open-specific state in filep->f_priv */
+
+  filep->f_priv = attr;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: fdt_close
+ ****************************************************************************/
+
+static int fdt_close(FAR struct file *filep)
+{
+  FAR struct fdt_file_s *attr;
+
+  /* Recover our private data from the struct file instance */
+
+  attr = filep->f_priv;
+  DEBUGASSERT(attr);
+
+  /* Release the file attributes structure */
+
+  kmm_free(attr);
+  filep->f_priv = NULL;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: fdt_read
+ ****************************************************************************/
+
+static ssize_t fdt_read(FAR struct file *filep, FAR char *buffer,
+                        size_t buflen)
+{
+  FAR const char *fdt;
+  FAR struct fdt_header_s *fdt_header;
+  off_t offset;
+  ssize_t ret;
+
+  finfo("buffer=%p buflen=%zu\n", buffer, buflen);
+  DEBUGASSERT(filep != NULL && buffer != NULL && buflen > 0);
+
+  /* Load FDT and parse extents. */
+
+  fdt = fdt_get();
+  if (fdt == NULL)
+    {
+      ferr("FDT cannot be read.\n");
+      return -ENOENT;
+    }
+
+  /* Transfer the fdt to user receive buffer */
+
+  fdt_header = (struct fdt_header_s *)fdt;
+  offset = filep->f_pos;
+  ret = procfs_memcpy(fdt, be32toh(fdt_header->totalsize),
+                      buffer, buflen, &offset);
+
+  /* Update the file offset */
+
+  if (ret > 0)
+    {
+      filep->f_pos += ret;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: fdt_dup
+ *
+ * Description:
+ *   Duplicate open file data in the new file structure.
+ *
+ ****************************************************************************/
+
+static int fdt_dup(FAR const struct file *oldp, FAR struct file *newp)
+{
+  FAR struct fdt_file_s *oldattr;
+  FAR struct fdt_file_s *newattr;
+
+  finfo("Dup %p->%p\n", oldp, newp);
+
+  /* Recover our private data from the old struct file instance */
+
+  oldattr = oldp->f_priv;
+  DEBUGASSERT(oldattr);
+
+  /* Allocate a new container to hold the task and attribute selection */
+
+  newattr = kmm_malloc(sizeof(struct fdt_file_s));
+  if (newattr == NULL)
+    {
+      ferr("ERROR: Failed to allocate file attributes\n");
+      return -ENOMEM;
+    }
+
+  /* The copy the file attributes from the old attributes to the new */
+
+  memcpy(newattr, oldattr, sizeof(struct fdt_file_s));
+
+  /* Save the new attributes in the new file structure */
+
+  newp->f_priv = newattr;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: fdt_stat
+ *
+ * Description: Return information about a file or directory
+ *
+ ****************************************************************************/
+
+static int fdt_stat(FAR const char *relpath, FAR struct stat *buf)
+{
+  /* "fdt" is the name for a read-only file */
+
+  memset(buf, 0, sizeof(struct stat));
+  buf->st_mode = S_IFREG | S_IROTH | S_IRGRP | S_IRUSR;
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+#endif /* CONFIG_DEVICE_TREE && CONFIG_FS_PROCFS_EXCLUDE_FDT */

include/nuttx/fdt.h

@@ -0,0 +1,88 @@
+/****************************************************************************
+ * include/nuttx/fdt.h
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_FDT_H
+#define __INCLUDE_NUTTX_FDT_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <nuttx/compiler.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define FDT_MAGIC 0xd00dfeed
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+struct fdt_header_s
+{
+  uint32_t magic;
+  uint32_t totalsize;
+  uint32_t off_dt_struct;
+  uint32_t off_dt_strings;
+  uint32_t off_mem_rsvmap;
+  uint32_t version;
+  uint32_t last_comp_version;
+  uint32_t boot_cpuid_phys;
+  uint32_t size_dt_strings;
+  uint32_t size_dt_struct;
+};
+
+/****************************************************************************
+ * Public Functions Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: fdt_register
+ *
+ * Description:
+ *   Store the pointer to the flattened device tree and verify that it at
+ *   least appears to be valid. This function will not fully parse the FDT.
+ *
+ * Return:
+ *   Return -EINVAL if the fdt header does not have the expected magic value.
+ *   otherwise return OK. If OK is not returned the existing entry for FDT
+ *   is not modified.
+ *
+ ****************************************************************************/
+
+int fdt_register(FAR const char *fdt_base);
+
+/****************************************************************************
+ * Name: fdt_get
+ *
+ * Description:
+ *   Return the pointer to a raw FDT. NULL is returned if no FDT has been
+ *   loaded.
+ *
+ ****************************************************************************/
+
+FAR const char *fdt_get(void);
+
+#endif /* __INCLUDE_NUTTX_FDT_H */