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Diffstat (limited to 'Documentation/libtracefs-cpu-open.txt')
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diff --git a/Documentation/libtracefs-cpu-open.txt b/Documentation/libtracefs-cpu-open.txt new file mode 100644 index 0000000..c5a900a --- /dev/null +++ b/Documentation/libtracefs-cpu-open.txt @@ -0,0 +1,100 @@ +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 <tracefs.h>* + +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* <rostedt@goodmis.org> +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +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). |