linux-kernel - Re: [PATCH v4 2/2] ThunderX2: Add Cavium ThunderX2 SoC UNCORE PMU driver

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Message-ID: <20180427093027.ngtuoezyh6mtz26p@lakrids.cambridge.arm.com>
Date:   Fri, 27 Apr 2018 10:30:27 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Kim Phillips <kim.phillips@....com>
Cc:     Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Will.Deacon@....com,
        jnair@...iumnetworks.com, Robert.Richter@...ium.com,
        Vadim.Lomovtsev@...ium.com, Jan.Glauber@...ium.com,
        gklkml16@...il.com
Subject: Re: [PATCH v4 2/2] ThunderX2: Add Cavium ThunderX2 SoC UNCORE PMU
 driver

Hi Kim,

On Thu, Apr 26, 2018 at 05:06:24PM -0500, Kim Phillips wrote:
> On Wed, 25 Apr 2018 14:30:47 +0530
> Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com> wrote:
> 
> > +static int thunderx2_uncore_event_init(struct perf_event *event)

> This PMU driver can be made more user-friendly by not just silently
> returning an error code such as -EINVAL, but by emitting a useful
> message describing the specific error via dmesg.

As has previously been discussed on several occasions, patches which log
to dmesg in a pmu::event_init() path at any level above pr_debug() are
not acceptable -- dmesg is not intended as a mechanism to inform users
of driver-specific constraints.

I would appreciate if in future you could qualify your suggestion with
the requirement that pr_debug() is used.

Thanks,
Mark.