| 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). |
