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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id l3sm15281429wru.36.2018.12.11.06.18.29 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 11 Dec 2018 06:18:30 -0800 (PST) Date: Tue, 11 Dec 2018 15:18:28 +0100 From: Ingo Molnar To: Quentin Perret Cc: peterz@infradead.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@codeaurora.org, skannan@codeaurora.org, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [PATCH v10 04/15] PM / EM: Expose the Energy Model in sysfs Message-ID: <20181211141827.GA85618@gmail.com> References: <20181203095628.11858-1-quentin.perret@arm.com> <20181203095628.11858-5-quentin.perret@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181203095628.11858-5-quentin.perret@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Quentin Perret wrote: > Expose the Energy Model (read-only) of all performance domains in sysfs > for convenience. To do so, add a kobject to the CPU subsystem under the > umbrella of which a kobject for each performance domain is attached. > > The resulting hierarchy is as follows for a platform with two > performance domains for example: > > /sys/devices/system/cpu/energy_model > ├── pd0 > │   ├── cost > │   ├── cpus > │   ├── frequency > │   └── power > └── pd4 > ├── cost > ├── cpus > ├── frequency > └── power > > In this implementation, the kobject abstraction is only used as a > convenient way of exposing data to sysfs. However, it could also be > used in the future to allocate and release performance domains in a more > dynamic way using reference counting. > > Cc: Peter Zijlstra > Cc: "Rafael J. Wysocki" > Signed-off-by: Quentin Perret > --- > include/linux/energy_model.h | 2 + > kernel/power/energy_model.c | 90 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 92 insertions(+) Why is a read-only ABI added for 'convenience'? We really don't do that as ABIs are final and they come with responsibilities. I think if this is for debug purposes it should be declared and put into debugfs or so. If it's for some other purpose that purpose should be declared. Thanks, Ingo