In order for a user application to make use of relay files, the
host filesystem must be mounted. For example,
- mount -t debugfs debugfs /debug
+ mount -t debugfs debugfs /sys/kernel/debug
NOTE: the host filesystem doesn't need to be mounted for kernel
clients to create or use channels - it only needs to be
(including in create_buf_file()) via chan->private_data or
buf->chan->private_data.
+Buffer-only channels
+--------------------
+
+These channels have no files associated and can be created with
+relay_open(NULL, NULL, ...). Such channels are useful in scenarios such
+as when doing early tracing in the kernel, before the VFS is up. In these
+cases, one may open a buffer-only channel and then call
+relay_late_setup_files() when the kernel is ready to handle files,
+to expose the buffered data to the userspace.
+
Channel 'modes'
---------------