Re: [PATCH v5 04/30] tools/lib/traceevent: Man page for header_page APIs

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 12 Apr 2019 16:37:45 +0300
Tzvetomir Stoyanov <tstoyanov@vmware.com> wrote:

> Create a man page for libtraceevent APIs:
>   tep_get_header_page_size(),
>   tep_get_header_timestamp_size(),
>   tep_is_old_format()
> 
> Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
> ---
>  .../libtraceevent-header_page.txt             | 105 ++++++++++++++++++
>  1 file changed, 105 insertions(+)
>  create mode 100644 tools/lib/traceevent/Documentation/libtraceevent-header_page.txt
> 
> diff --git a/tools/lib/traceevent/Documentation/libtraceevent-header_page.txt b/tools/lib/traceevent/Documentation/libtraceevent-header_page.txt
> new file mode 100644
> index 000000000000..e1bd664ac123
> --- /dev/null
> +++ b/tools/lib/traceevent/Documentation/libtraceevent-header_page.txt
> @@ -0,0 +1,105 @@
> +libtraceevent(3)
> +================
> +
> +NAME
> +----
> +tep_get_header_page_size, tep_get_header_timestamp_size, tep_is_old_format -
> +Get the data stored in the header page, in kernel context.
> +
> +SYNOPSIS
> +--------
> +[verse]
> +--
> +*#include <event-parse.h>*
> +
> +int *tep_get_header_page_size*(struct tep_handle pass:[*]_tep_);
> +int *tep_get_header_timestamp_size*(struct tep_handle pass:[*]_tep_);
> +bool *tep_is_old_format*(struct tep_handle pass:[*]_tep_);
> +--
> +DESCRIPTION
> +-----------
> +These functions retrieve information from kernel context, stored in
> +/sys/kernel/debug/tracing/events/header_page. Old kernels do not have header

Let's avoid using full path names. This should be:

 stored in the tracefs events/header_page.


> +page info, so default values from user space context are used.
> +
> +The _tep_get_header_page_size()_ function returns the size of a long integer,
> +in kernel context. The _tep_ argument is trace event parser context.
> +This information is retrieved from /sys/kernel/debug/tracing/events/header_page,

Same here.

> + "commit" field.
> +
> +The _tep_get_header_timestamp_size()_ function returns the size of timestamps,
> +in kernel context. The _tep_ argument is trace event parser context.
> +This information is retrieved from /sys/kernel/debug/tracing/events/header_page,

and here.

> + "timestamp" field.
> +
> +The _tep_is_old_format()_ function  returns if the kernel is old one and has no

The _tep_is_old_format()_ function returns true if the kernel predates
the addition of events/header_page, otherwise it returns false.


> +/sys/kernel/debug/tracing/events/header_page.
> +
> +RETURN VALUE
> +------------
> +The _tep_get_header_page_size()_ function returns the size of a long integer,
> +in bytes.
> +
> +The _tep_get_header_timestamp_size()_ function returns the size of timestamps,
> +in bytes.
> +
> +The _tep_is_old_format()_ function returns true, if an old kernel is used to
> +generate the tracing data, which has no
> +/sys/kernel/debug/tracing/events/header_page. If the kernel is new, or _tep_ is

Just say "no event/header_page"

-- Steve

> +NULL, false is returned.
> +
> +EXAMPLE
> +-------
> +[source,c]
> +--
> +#include <event-parse.h>
> +...
> +struct tep_handle *tep = tep_alloc();
> +...
> +	int longsize;
> +	int timesize;
> +	bool old;
> +
> +	longsize = tep_get_header_page_size(tep);
> +	timesize = tep_get_header_timestamp_size(tep);
> +	old = tep_is_old_format(tep);
> +
> +	printf ("%s kernel is used to generate the tracing data.\n",
> +		old?"Old":"New");
> +	printf("The size of a long integer is %d bytes.\n", longsize);
> +	printf("The timestamps size is %d bytes.\n", timesize);
> +...
> +--
> +
> +FILES
> +-----
> +[verse]
> +--
> +*event-parse.h*
> +	Header file to include in order to have access to the library APIs.
> +*-ltraceevent*
> +	Linker switch to add when building a program that uses the library.
> +--
> +
> +SEE ALSO
> +--------
> +_libtraceevent(3)_, _trace-cmd(1)_
> +
> +AUTHOR
> +------
> +[verse]
> +--
> +*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
> +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
> +--
> +REPORTING BUGS
> +--------------
> +Report bugs to  <linux-trace-devel@vger.kernel.org>
> +
> +LICENSE
> +-------
> +libtraceevent is Free Software licensed under the GNU LGPL 2.1
> +
> +RESOURCES
> +---------
> +https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git