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    SubjectRe: [PATCH v4 3/3] media: atomisp: Only use trace_printk if allowed
    On Fri, 21 Aug 2020 08:13:00 +0800
    Nicolas Boichat <drinkcat@chromium.org> wrote:

    > On Thu, Aug 20, 2020 at 10:23 PM Steven Rostedt <rostedt@goodmis.org> wrote:
    > >
    > > On Thu, 20 Aug 2020 17:14:12 +0800
    > > Nicolas Boichat <drinkcat@chromium.org> wrote:
    > >
    > > > Technically, we could only initialize the trace_printk buffers
    > > > when the print env is switched, to avoid the build error and
    > > > unconditional boot-time warning, but I assume this printing
    > > > framework will eventually get removed when the driver moves out
    > > > of staging?
    > >
    > > Perhaps this should be converting into a trace event. Look at what bpf
    > > did for their bpf_trace_printk().
    > >
    > > The more I think about it, the less I like this series.
    >
    > To make it clear, the primary goal of this series is to get rid of
    > trace_printk sprinkled in the kernel by making sure some randconfig
    > builds fail. Since my v2, there already has been one more added (the
    > one that this patch removes), so I'd like to land 2/3 ASAP to prevent
    > even more from being added.
    >
    > Looking at your reply on 1/3, I think we are aligned on that goal? Is
    > there some other approach you'd recommend?
    >
    > Now, I'm not pretending my fixes are the best possible ones, but I
    > would much rather have the burden of converting to trace events on the
    > respective driver maintainers. (btw is there a short
    > documentation/tutorial that I could link to in these patches, to help
    > developers understand what is the recommended way now?)
    >

    I like the goal, but I guess I never articulated the problem I have
    with the methodology.

    trace_printk() is meant to be a debugging tool. Something that people
    can and do sprinkle all over the kernel to help them find a bug in
    areas that are called quite often (where printk() is way too slow).

    The last thing I want them to deal with is adding a trace_printk() with
    their distro's config (or a config from someone that triggered the bug)
    only to have the build to fail, because they also need to add a config
    value.

    I add to the Cc a few developers I know that use trace_printk() in this
    fashion. I'd like to hear their view on having to add a config option
    to make trace_printk work before they test a config that is sent to
    them.

    -- Steve

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