Re: [PATCH] libtracefs: An API to set the filtering of functions

[Tzvetomir Stoyanov <tz.stoyanov@gmail.com>]

On Thu, Mar 4, 2021 at 9:24 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 3 Mar 2021 06:46:26 +0530
> Sameeruddin Shaik <sameeruddin.shaik8@gmail.com> wrote:
>
> > what if we store the indices of the failed filters in an integer array
> > and return them back?
>
> There's not much difference if we return an array of pointers to the
> filters or an array of integers to the index. I was just thinking about
> how I would use the interface. When having a working interface, we
> should write a few robust programs to see how easy it is to use, and
> that will help in making the API appropriate. This needs to be done
> *before* we accept it. This particular API is going to be widely used,
> and it needs to be simple and robust.

One remark, not directly related to this discussion. When the implementation
of the API is ready, there should be a unit test (in a separate patch) - as for
any of the other APIs. Usually these are the first use cases that I write for
the new APIs.
Sameer, please look at utest directory where the unit tests are, each API has
a unit test there. We use the cunit framework, ask if there are questions about
it. This should be the next step, when the final version of the
implementation is
ready.
Thanks!

>
> > let's return the number of bytes written, also we will calculate the
> > complete filters length and return it, if there is difference,
> > we will loop into the integer array and print the erroneous filters
>
> Not sure how that is helpful. How would you use the number of bytes
> written?
>
> >
> > Let's fix the number of parameters to this function:)
>
> Not sure what you mean by that.
>
>
> Here's how I envision this interface.
>
>         char **errs;
>         char *filters[] = {
>                 "sched*", "spin_*", NULL
>         };
>         int ret;
>
>
>         ret = tracefs_function_filter(NULL, filters, NULL, &errs);
>         if (ret < 0) {
>                 int i;
>
>                 printf("Failed to apply: ");
>                 for (i = 0; errs[i]; i++) {
>                         if (i)
>                                 printf(", ");
>                         printf("'%s'", errs[i]);
>                 }
>                 printf("\n";
>                 exit(ret);
>         }
>
> -- Steve



-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center