Documentation update for creating relay files in other filesystems.
Signed-off-by: Tom Zanussi <[email protected]>
---
relayfs.txt | 27 +++++++++++++++++++++++++++
1 files changed, 27 insertions(+)
diff --git a/Documentation/filesystems/relayfs.txt b/Documentation/filesystems/relayfs.txt
--- a/Documentation/filesystems/relayfs.txt
+++ b/Documentation/filesystems/relayfs.txt
@@ -143,6 +143,8 @@ Here's a summary of the API relayfs prov
subbuf_start(buf, subbuf, prev_subbuf, prev_padding)
buf_mapped(buf, filp)
buf_unmapped(buf, filp)
+ create_buf_file(filename, parent, mode, buf)
+ remove_buf_file(dentry)
helper functions:
@@ -343,6 +345,31 @@ completely defined by the caller.
See the relay-apps tarball at http://relayfs.sourceforge.net for
examples of how these non-relay files are meant to be used.
+Creating relay files in other filesystems
+-----------------------------------------
+
+By default of course, relay_open() creates relay files in the relayfs
+filesystem. Because relay_file_operations is exported, however, it's
+also possible to create and use relay files in other pseudo-filesytems
+such as debugfs.
+
+For this purpose, two callback functions are provided,
+create_buf_file() and remove_buf_file(). create_buf_file() is called
+once for each per-cpu buffer from relay_open() to allow the client to
+create a file to be used to represent the corresponding buffer; if
+this callback is not defined, the default implementation will create
+and return a file in the relayfs filesystem to represent the buffer.
+The callback should return the dentry of the file created to represent
+the relay buffer. Note that the parent directory passed to
+relay_open() (and passed along to the callback), if specified, must
+exist in the same filesystem the new relay file is created in. If
+create_buf_file() is defined, remove_buf_file() must also be defined;
+it's responsible for deleting the file(s) created in create_buf_file()
+and is called during relay_close().
+
+See the 'exported-relayfile' examples in the relay-apps tarball for
+examples of creating and using relay files in debugfs.
+
Misc
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