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Message-ID: <20190904161737.GA20662@kroah.com> References: <20190829213321.4092-1-mike.leach@linaro.org> <20190829213321.4092-10-mike.leach@linaro.org> <20190903195951.GA25008@kroah.com> <20190904054809.GB4511@kroah.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190904_091740_837129_03ED8DB1 X-CRM114-Status: GOOD ( 28.41 ) 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: Jon Corbet , Coresight ML , "open list:DOCUMENTATION" , linux-arm-kernel , "Suzuki K. Poulose" , Mike Leach 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 Wed, Sep 04, 2019 at 10:05:51AM -0600, Mathieu Poirier wrote: > On Tue, 3 Sep 2019 at 23:48, Greg KH wrote: > > > > On Tue, Sep 03, 2019 at 04:51:40PM -0600, Mathieu Poirier wrote: > > > On Tue, 3 Sep 2019 at 13:59, Greg KH wrote: > > > > > > > > On Thu, Aug 29, 2019 at 10:33:19PM +0100, Mike Leach wrote: > > > > > Update document to include the new sysfs features added during this > > > > > patchset. > > > > > > > > > > Updated to reflect the new sysfs component nameing schema. > > > > > > > > > > Signed-off-by: Mike Leach > > > > > --- > > > > > .../testing/sysfs-bus-coresight-devices-etm4x | 183 +++++++++++------- > > > > > 1 file changed, 115 insertions(+), 68 deletions(-) > > > > > > > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x > > > > > index 36258bc1b473..112c50ae9986 100644 > > > > > --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x > > > > > +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x > > > > > @@ -1,4 +1,4 @@ > > > > > -What: /sys/bus/coresight/devices/.etm/enable_source > > > > > +What: /sys/bus/coresight/devices/etm/enable_source > > > > > > > > You are renaming sysfs directories that have been around since: > > > > > > > > > Date: April 2015 > > > > > > > > ??? > > > > > > > > Really? > > > > > > > > That's brave. > > > > > > > > > When I worked on the coresight sysfs ABI a while back I specifically > > > added it at the "testing" level as I was well aware that things could > > > change in the future. According to the guidelines in the > > > documentation userspace can rely on it which was accurate since the > > > interface didn't change for 4 years. But the guidelines also mention > > > that changes can occur before the interfaces are move to stables, and > > > that programs are encouraged to manifest their interest by adding > > > their name to the "users" field. > > > > > > The interface was changed in 5.2 to support coresight from ACPI and > > > make things easier to understand for users. It is a lot more > > > intuitive to associate an ETM tracer with the CPU it belongs to by > > > referring to the CPU number than the memory mapped address. Given the > > > "testing" status of the interface and the absence of registered users > > > I decided to move forward with the change. If "testing" is too strict > > > for that I suggest to add an "experimental" category where it would be > > > more acceptable to change things as subsystems mature. > > > > "testing" is not really "testing" if you have userspace tools/programs > > assuming the location and contents of specific files in sysfs. > > > > You can change things in sysfs by creating new files, but to do > > wholesale renaming like you did here can be very dangerous as you might > > be breaking things. > > Yes, something I have definitely considered. > > > Usually new files are created, not existing ones > > moved. > > In this case it would have meant a new symbolic link for every > coresight device, so twice a many entries under > $(SYS)/bus/coresight/device/. That would have been a lot of clutter > and an increasing source of problems as the number of CPU and sinks > increases. To me, and given the permissive definition of "testing" > found in the documentation, a clean break was a better option. Well, "testing" doesn't really matter in the end, if a tool/user relies on it, we have to keep it working properly. > > What tools use these today? What is going to break? > > Other than local shell scripts I am not aware of any tools using these > today. I am certainly open to discuss a better alternative but right > now, I just don't see one. Be aware that you might have to change this back if there is any objections. thanks, greg k-h _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel