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

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Message-Id: <20180427081525.f9dcc756678baf3bb6e6e473@arm.com>
Date:   Fri, 27 Apr 2018 08:15:25 -0500
From:   Kim Phillips <kim.phillips@....com>
To:     Mark Rutland <mark.rutland@....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

On Fri, 27 Apr 2018 10:30:27 +0100
Mark Rutland <mark.rutland@....com> wrote:

> 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 disagree - drivers do it all the time, using dev_err(), dev_warn(), etc.

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

It shouldn't - the driver isn't being debugged, it's in regular use.

Thanks,

Kim