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Wysocki" Subject: Re: [PATCH] cpufreq: Add user_min/max_freq Message-ID: <20191031222356.GE27773@google.com> References: <3169109.BFaCN5124U@kreacher> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <3169109.BFaCN5124U@kreacher> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191031_152359_638509_774AFA5C X-CRM114-Status: GOOD ( 14.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ulf Hansson , Saravana Kannan , linux-pm@vger.kernel.org, Viresh Kumar , Chanwoo Choi , Kyungmin Park , MyungJoo Ham , Leonard Crestez , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 31, 2019 at 11:24:31AM +0100, Rafael J. Wysocki wrote: > On Wednesday, October 30, 2019 1:41:49 AM CET Leonard Crestez wrote: > > Current values in scaling_min_freq and scaling_max freq can change on > > the fly due to event such as thermal monitoring. > > Which is intentional. > > > This behavior is confusing for userspace and because once an userspace > > limit is written to scaling_min/max_freq it is not possible to read it back. > > That can be argued both ways. > > It is also useful to know the effective constraints and arguably the ability > to read back the values that you have written is mostly needed for debugging > the code. Agreed that reading the values back is probably mostly useful for debugging. Reading the effective constraints is a debugging use case as well, userspace can't make any decisions based on values which might be in constant flux. IMO the current interface is completely counterintuitive, I really hope we wouldn't implement it the same way if given a chance to do it again. If there is use for reading the effective constraints it should be exposed as a separate read-only attribute. Keep it simple (when possible). _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel