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Added information on the evaluate and evaluate for make routines.
Added details on how generic code starts the pathevaluation process.
This commit is contained in:
Jennifer Averett
@@ -326,16 +326,28 @@ typedef struct @{
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@subheading Corresponding Structure Element:
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XXX
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evalpath
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@subheading Arguments:
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XXX
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@example
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const char *pathname, /* IN */
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int flags, /* IN */
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rtems_filesystem_location_info_t *pathloc /* IN/OUT */
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@end example
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@subheading Description:
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XXX
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This routine is responsible for evaluating the pathname passed in
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based upon the flags and the valid @code{rthems_filesystem_location_info_t}.
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Additionally, it must make any changes to pathloc necessary to identify
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the pathname node. This should include calling the evalpath for a mounted
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filesystem, if the given filesystem supports the mount command.
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This routine returns a 0 if the evaluation was successful.
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Otherwise, it returns a -1 and sets errno to the correct error.
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This routine is required and should NOT be set to NULL.
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@c
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@c
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@@ -346,16 +358,31 @@ XXX
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@subheading Corresponding Structure Element:
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XXX
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evalformake
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@subheading Arguments:
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XXX
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@example
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const char *path, /* IN */
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rtems_filesystem_location_info_t *pathloc, /* IN/OUT */
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const char **name /* OUT */
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@end example
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@subheading Description:
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XXX
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This method is given a path to evaluate and a valid start location. It
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is responsible for finding the parent node for a requested make command,
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setting pathloc information to identify the parent node, and setting
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the name pointer to the first character of the name of the new node.
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Additionally, if the filesystem supports the mount command, this method
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should call the evalformake routine for the mounted filesystem.
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This routine returns a 0 if the evaluation was successful. Otherwise, it
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returns a -1 and sets errno to the correct error.
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This routine is required and should NOT be set to NULL. However, if
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the filesystem does not support user creation of a new node, it may
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set errno to ENOSYS and return -1.
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@c
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@c
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@@ -388,6 +415,8 @@ If the link count exceeds LINK_MAX an error will be returned.
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The name of the link will be normalized to remove extraneous separators from
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the end of the name.
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This routine is not required and may be set to NULL.
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@c
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@c
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@c
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@@ -8,38 +8,103 @@
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@chapter Pathname Evaluation
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This chapter describes the pathname evaluation process for the
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RTEMS Filesystem Infrastructure.
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@example
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XXX Include graphic of the path evaluation process with Jennifer's
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explanations
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XXX explanations
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@end example
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@itemize @bullet
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@section Pathname Evaluation Handlers
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@item There are two pathname evaluation routines. The handler patheval()
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There are two pathname evaluation routines. The handler patheval()
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is called to find, verify privlages on and return information on a node
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that exists. The handler evalformake() is called to find, verify
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permissions, and return information on a node that is to become a parent.
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Additionally, evalformake() returns a pointer to the start of the name of
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the new node to be created.
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@item Pathname evaluation is specific to a filesystem
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Pathname evaluation is specific to a filesystem.
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Each filesystem is required to provide both a patheval() and an evalformake()
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routine. Both of these routines gets a name to evaluate and a node indicating
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where to start the evaluation.
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@section Crossing a Mount Point During Path Evaluation
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If the filesystem supports the mount command, the evaluate routines
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must handle crossing the mountpoint. The evaluate routine should evaluate
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the name upto the first directory node where the new filesystem is mounted.
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The filesystem may process terminator characters prior to calling the
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evaluate routine for the new filesystem. A pointer to the portion of the
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name which has not been evaluated along with the root node of the new
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file system ( gotten from the mount table entry ) is passed to the correct
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mounted filesystem evaluate routine.
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@section The rtems_filesystem_location_info_t Structure
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The @code{rtems_filesystem_location_info_t} structure contains all information
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necessary for identification of a node.
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The generic rtems filesystem code defines two global
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rtems_filesystem_location_info_t structures, the
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@code{rtems_filesystem_root} and the @code{rtems_filesystem_current}.
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Both are initially defined to be the root node of the base filesystem.
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Once the chdir command is correctly used the @code{rtems_filesystem_current}
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is set to the location specified by the command.
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The filesystem generic code peeks at the first character in the name to be
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evaluated. If this character is a valid seperator, the
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@code{rtems_filesystem_root} is used as the node to start the evaluation
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with. Otherwise, the @code{rtems_filesystem_current} node is used as the
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node to start evaluating with. Therefore, a valid
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rtems_filesystem_location_info_t is given to the evaluate routine to start
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evaluation with. The evaluate routines are then responsible for making
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any changes necessary to this structure to correspond to the name being
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parsed.
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@example
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struct rtems_filesystem_location_info_tt @{
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void *node_access;
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rtems_filesystem_file_handlers_r *handlers;
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rtems_filesystem_operations_table *ops;
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rtems_filesystem_mount_table_entry_t *mt_entry;
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@};
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@end example
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@table @b
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@item node_access
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This element is filesystem specific. A filesystem can define and store
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any information necessary to identify a node at this location. This element
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is normally filled in by the filesystem's evaluate routine. For the
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filesystem's root node, the filesystem's initilization routine should
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fill this in, and it should remain valid until the instance of the
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filesystem is unmounted.
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@item handlers
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This element is defined as a set of routines that may change within a
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given filesystem based upon node type. For example a directory and a
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memory file may have to completely different read routines. This element
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is set to an initialization state defined by the mount table, and may
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be set to the desired state by the evaluation routines.
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@item ops
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This element is defined as a set of routines that remain static for the
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filesystem. This element identifies entry points into the filesystem
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to the generic code.
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@item mt_entry
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This element identifies the mount table entry for this instance of the
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filesystem.
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@end table
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@item Mechanics of crossing a mount point during the evaluation of a path
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name
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@item Role of rtems_filesystem_location_info_t structure
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@itemize @bullet
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@item Finding filesystem node information
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@item Finding filesystem node handlers
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@item Finding filesystem node operations table
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@item Finding mount table entry for the filesystem that this node is part
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of
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@end itemize
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@end itemize
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