libtracefs(3) ============= NAME ---- tracefs_cpu_open, tracefs_cpu_close, tracefs_cpu_alloc_fd, tracefs_cpu_free_fd - Opening trace_pipe_raw data for reading SYNOPSIS -------- [verse] -- *#include * struct tracefs_cpu pass:[*]*tracefs_cpu_open*(struct tracefs_instance pass:[*]_instance_, int _cpu_, bool _nonblock_); void *tracefs_cpu_close*(struct tracefs_cpu pass:[*]_tcpu_); struct tracefs_cpu pass:[*]*tracefs_cpu_alloc_fd*(int _fd_, int _subbuf_size_, bool _nonblock_); void *tracefs_cpu_free_fd*(struct tracefs_cpu pass:[*]_tcpu_); -- DESCRIPTION ----------- This set of APIs can be used to open the raw data from the trace_pipe_raw files in the tracefs file system in oder to read them with the *tracefs_cpu_read*(3) functions. The *tracefs_cpu_open()* creates a descriptor that can read the tracefs trace_pipe_raw file for a given _cpu_ in a given _instance_. If _instance_ is NULL than the toplevel trace_pipe_raw file is used. The *tracefs_cpu_close()* closes all the file descriptors associated to the trace_pipe_raw opened by *tracefs_cpu_open()*. The *tracefs_cpu_alloc_fd()* will create a tracefs_cpu descriptor from an existing file descriptor _fd_. This is useful to use when connecting to a socket or pipe where the other end is feeding raw tracing data in the same format as the trace_pipe_raw file would (like in guest to host tracing). The caller is responsible for determining the _subbuf_size_ that will be used to break up the sub-buffers being read by the file descriptor. The _nonblock_ is treated the same as the same parameter in *tracefs_cpu_open()*. The *tracefs_cpu_free_fd()* is used to free the descriptor returned by *tracefs_cpu_alloc_fd()*. It does all the clean up that *tracefs_cpu_close()* performs, and that could also be used to free up the descriptor created by *tracefs_cpu_alloc_fd()* but will also close the file descriptor passed in. Note that *tracefs_cpu_free_fd()* should not be used on the descriptor returned by *tracefs_cpu_open()* as it will not close the file descriptor created by it. RETURN VALUE ------------ The *tracefs_cpu_open()* returns a struct tracefs_cpu descriptor that can be used by the other functions or NULL on error. The *tracefs_cpu_alloc_fd()* returns a struct tracefs_cpu descriptor that can be used by the *tracefs_cpu_read*(3) related functions, where the descriptor will be reading the passed in _fd_ file descriptor. EXAMPLE ------- See *tracefs_cpu_read*(3) for an example. FILES ----- [verse] -- *tracefs.h* Header file to include in order to have access to the library APIs. *-ltracefs* Linker switch to add when building a program that uses the library. -- SEE ALSO -------- *libtracefs*(3), *libtraceevent*(3), *trace-cmd*(1) AUTHOR ------ [verse] -- *Steven Rostedt* -- REPORTING BUGS -------------- Report bugs to LICENSE ------- libtracefs is Free Software licensed under the GNU LGPL 2.1 RESOURCES --------- https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ COPYING ------- Copyright \(C) 2022 Google, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).