From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christopher Covington Subject: Re: [PATCH 10/11] coresight-etm4x: Controls pertaining to the context ID functions Date: Thu, 23 Apr 2015 12:59:51 -0400 Message-ID: <55392507.1030103@codeaurora.org> References: <1429742451-11465-1-git-send-email-mathieu.poirier@linaro.org> <1429742451-11465-11-git-send-email-mathieu.poirier@linaro.org> <55390B05.1050801@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mathieu Poirier Cc: Greg KH , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Kaixu Xia , Chunyan Zhang List-Id: linux-api@vger.kernel.org On 04/23/2015 11:16 AM, Mathieu Poirier wrote: > On 23 April 2015 at 09:08, Christopher Covington wrote: >> Hi Mathieu, >> >> On 04/22/2015 06:40 PM, Mathieu Poirier wrote: >>> From: Pratik Patel >>> >>> Adding sysfs entries to access and configure specifics about the >>> context ID comparator functions. >>> >>> Signed-off-by: Pratik Patel >>> Signed-off-by: Mathieu Poirier >>> --- >>> .../ABI/testing/sysfs-bus-coresight-devices-etm4x | 19 +++ >>> drivers/hwtracing/coresight/coresight-etm4x.c | 187 +++++++++++++++++++++ >>> 2 files changed, 206 insertions(+) >>> >>> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x >>> index b5c0456290ab..8b32cb7b9723 100644 >>> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x >>> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x >>> @@ -254,3 +254,22 @@ Date: April 2015 >>> KernelVersion: 4.01 >>> Contact: Mathieu Poirier >>> Description: (RW) Controls the selection of the resources in the trace unit. >>> + >>> +What: /sys/bus/coresight/devices/.etm/ctxid_idx >>> +Date: April 2015 >>> +KernelVersion: 4.01 >>> +Contact: Mathieu Poirier >>> +Description: (RW) Select which context ID comparator to work with. >>> + >>> +What: /sys/bus/coresight/devices/.etm/ctxid_val >>> +Date: April 2015 >>> +KernelVersion: 4.01 >>> +Contact: Mathieu Poirier >>> +Description: (RW) Get/Set the context ID comparator value to trigger on. >> >> If I'm understanding this correctly, ctxid_val is multiplexed using ctxid_idx. >> Why not just have ctxid_val0, ctxid_val1, ...? > > There can be up to 8 of them on the current implementation and who > knows how many more in the future. To me using and index to select > the context ID to work on scaled better and is introducing less > clutter in sysfs. In theory there's a race condition if two tasks are trying to set the index and then the value, which having individually addressable values solves, but I don't anticipate trying to use more than one task to configure tracing. Chris -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project