linux-kernel - Re: [PATCH 10/11] coresight-etm4x: Controls pertaining to the context ID functions

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Date:	Thu, 23 Apr 2015 09:16:05 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	Christopher Covington <cov@...eaurora.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-api@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kaixu Xia <kaixu.xia@...aro.org>,
	Chunyan Zhang <zhang.chunyan@...aro.org>
Subject: Re: [PATCH 10/11] coresight-etm4x: Controls pertaining to the context
 ID functions

On 23 April 2015 at 09:08, Christopher Covington <cov@...eaurora.org> wrote:
> Hi Mathieu,
>
> On 04/22/2015 06:40 PM, Mathieu Poirier wrote:
>> From: Pratik Patel <pratikp@...eaurora.org>
>>
>> Adding sysfs entries to access and configure specifics about the
>> context ID comparator functions.
>>
>> Signed-off-by: Pratik Patel <pratikp@...eaurora.org>
>> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>> ---
>>  .../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 <mathieu.poirier@...aro.org>
>>  Description:         (RW) Controls the selection of the resources in the trace unit.
>> +
>> +What:                /sys/bus/coresight/devices/<memory_map>.etm/ctxid_idx
>> +Date:                April 2015
>> +KernelVersion:       4.01
>> +Contact:     Mathieu Poirier <mathieu.poirier@...aro.org>
>> +Description: (RW) Select which context ID comparator to work with.
>> +
>> +What:                /sys/bus/coresight/devices/<memory_map>.etm/ctxid_val
>> +Date:                April 2015
>> +KernelVersion:       4.01
>> +Contact:     Mathieu Poirier <mathieu.poirier@...aro.org>
>> +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.

Thanks for the review,
Mathieu

>
> Thanks,
> Chris
>
> --
> Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
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