imfs: Replace devfs with an IMFS specialization

Add a simplified path evaluation function IMFS_eval_path_devfs() for a
device only IMFS configuration.

The code size can be further reduced by the application if it disables
the support for legacy IO drivers via:

  #define CONFIGURE_IMFS_DISABLE_MKNOD
  #define CONFIGURE_IMFS_DISABLE_MKNOD_DEVICE

Obsolete CONFIGURE_MAXIMUM_DEVICES.  Remove BSP_MAXIMUM_DEVICES.

Update #3894.
Update #3898.

1 files changed, 163 insertions, 0 deletions

diff --git a/cpukit/libfs/src/imfs/imfs_eval_devfs.c b/cpukit/libfs/src/imfs/imfs_eval_devfs.c
new file mode 100644
index 0000000000..d25e4ff8e2
--- /dev/null
+++ b/cpukit/libfs/src/imfs/imfs_eval_devfs.c
@@ -0,0 +1,163 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup ClassicIO
+ *
+ * @brief Implementation of IMFS_eval_path_devfs().
+ */
+
+/*
+ * Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/imfs.h>
+
+#include <string.h>
+
+typedef struct {
+  uint8_t len;
+  char name[3];
+} IMFS_devfs_dir;
+
+static const IMFS_devfs_dir IMFS_devfs_dirs[] = {
+  { .len = 1, .name = { '/' } },
+  { .len = 1, .name = { '.' } },
+  { .len = 2, .name = { '.', '.' } },
+  { .len = 3, .name = { 'd', 'e', 'v' } }
+};
+
+static IMFS_jnode_t *IMFS_devfs_is_dir(
+  rtems_filesystem_eval_path_context_t *ctx,
+  IMFS_directory_t                     *dir
+)
+{
+  const char *path;
+  size_t      pathlen;
+  size_t      i;
+
+  path = rtems_filesystem_eval_path_get_path( ctx );
+  pathlen = rtems_filesystem_eval_path_get_pathlen( ctx );
+
+  for ( i = 0; i < RTEMS_ARRAY_SIZE( IMFS_devfs_dirs ); ++i ) {
+    bool match;
+
+    match = IMFS_devfs_dirs[ i ].len == pathlen
+      && memcmp( IMFS_devfs_dirs[ i ].name, path, pathlen ) == 0;
+
+    if ( match ) {
+      int eval_flags;
+
+      eval_flags = rtems_filesystem_eval_path_get_flags( ctx );
+      eval_flags &= ~RTEMS_FS_EXCLUSIVE;
+      rtems_filesystem_eval_path_set_flags( ctx, eval_flags );
+      rtems_filesystem_eval_path_clear_path( ctx );
+      return &dir->Node;
+    }
+  }
+
+  return NULL;
+}
+
+static IMFS_jnode_t *IMFS_devfs_search(
+  rtems_filesystem_eval_path_context_t *ctx,
+  IMFS_directory_t                     *dir
+)
+{
+  const char          *path;
+  size_t               pathlen;
+  rtems_chain_control *entries;
+  rtems_chain_node    *current;
+  rtems_chain_node    *tail;
+
+  path = rtems_filesystem_eval_path_get_path( ctx );
+  pathlen = rtems_filesystem_eval_path_get_pathlen( ctx );
+  entries = &dir->Entries;
+  current = rtems_chain_first( entries );
+  tail = rtems_chain_tail( entries );
+
+  while ( current != tail ) {
+    IMFS_jnode_t *entry;
+    bool          match;
+
+    entry = (IMFS_jnode_t *) current;
+    match = entry->namelen == pathlen
+      && memcmp( entry->name, path, pathlen ) == 0;
+
+    if ( match ) {
+      return entry;
+    }
+
+    current = rtems_chain_next( current );
+  }
+
+  return NULL;
+}
+
+void IMFS_eval_path_devfs( rtems_filesystem_eval_path_context_t *ctx )
+{
+  rtems_filesystem_location_info_t *currentloc;
+  IMFS_directory_t                 *dir;
+  IMFS_jnode_t                     *entry;
+
+  currentloc = rtems_filesystem_eval_path_get_currentloc( ctx );
+  dir = currentloc->node_access;
+
+  entry = IMFS_devfs_is_dir( ctx, dir );
+
+  if ( entry != NULL ) {
+    return;
+  }
+
+  entry = IMFS_devfs_search( ctx, dir );
+
+  if ( entry != NULL ) {
+    int eval_flags;
+
+    eval_flags = rtems_filesystem_eval_path_get_flags( ctx );
+
+    if ( ( eval_flags & RTEMS_FS_EXCLUSIVE ) == 0 ) {
+      --dir->Node.reference_count;
+      ++entry->reference_count;
+      currentloc->node_access = entry;
+      currentloc->node_access_2 = IMFS_generic_get_context_by_node( entry );
+      IMFS_Set_handlers( currentloc );
+      rtems_filesystem_eval_path_clear_path( ctx );
+    } else {
+      rtems_filesystem_eval_path_error( ctx, EEXIST );
+    }
+  } else {
+    rtems_filesystem_eval_path_set_token(
+      ctx,
+      rtems_filesystem_eval_path_get_path( ctx ),
+      rtems_filesystem_eval_path_get_pathlen( ctx )
+    );
+    rtems_filesystem_eval_path_clear_path( ctx );
+  }
+}