From: Tom Zanussi Documentation update for creating relay files in other filesystems. Signed-off-by: Tom Zanussi Signed-off-by: Andrew Morton --- Documentation/filesystems/relayfs.txt | 27 +++++++++++++++++++++++++++ 1 files changed, 27 insertions(+) diff -puN Documentation/filesystems/relayfs.txt~relayfs-add-documentation-on-relay-files-in-other-filesystems Documentation/filesystems/relayfs.txt --- devel/Documentation/filesystems/relayfs.txt~relayfs-add-documentation-on-relay-files-in-other-filesystems 2005-11-12 13:18:14.000000000 -0800 +++ devel-akpm/Documentation/filesystems/relayfs.txt 2005-11-12 13:18:14.000000000 -0800 @@ -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 ---- _