linux-kernel - Re: [PATCH v5] stm: class: Add MIPI OST protocol support

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Message-ID: <7b02f748-7442-4272-b3b5-0dfff7c15e33@quicinc.com>
Date: Tue, 3 Feb 2026 10:31:21 +0800
From: "Yingchao Deng (Consultant)" <quic_yingdeng@...cinc.com>
To: Randy Dunlap <rdunlap@...radead.org>,
        Yingchao Deng
	<yingchao.deng@....qualcomm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers
	<mathieu.desnoyers@...icios.com>,
        Jonathan Corbet <corbet@....net>,
        "Alexander Shishkin" <alexander.shishkin@...ux.intel.com>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
CC: <linux-kernel@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        "Tingwei
 Zhang" <tingwei.zhang@....qualcomm.com>,
        Yuanfang Zhang
	<yuanfang.zhang@....qualcomm.com>,
        Jinlong Mao <jinlong.mao@....qualcomm.com>
Subject: Re: [PATCH v5] stm: class: Add MIPI OST protocol support


On 1/30/2026 2:38 AM, Randy Dunlap wrote:
>
> On 1/29/26 10:31 AM, Randy Dunlap wrote:
>> diff --git a/Documentation/trace/p_ost.rst b/Documentation/trace/p_ost.rst
>> new file mode 100644
>> index 000000000000..df93b889eb4c
>> --- /dev/null
>> +++ b/Documentation/trace/p_ost.rst
>> @@ -0,0 +1,36 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +===================
>> +MIPI OST over STP
>> +===================
>> +
>> +The OST(Open System Trace) driver is used with STM class devices to
>     The OST (Open System Trace) driver
>
>> +generate standardized trace stream. Trace sources can be identified
>> +by different entity ids.
>> +
>> +CONFIG_STM_PROTO_OST is for p_ost driver enablement. Once this config
>> +is enabled, you can select the p_ost protocol by command below:
>> +
>> +# mkdir /sys/kernel/config/stp-policy/stm0:p_ost.policy
>> +
>> +The policy name format is extended like this:
>> +    <device_name>:<protocol_name>.<policy_name>
>> +
>> +With coresight-stm device, it will be look like "stm0:p_ost.policy".
>     With {a | the} coresight-stm device,
>
>> +
>> +With MIPI OST protocol driver, the attributes for each protocol node is:
>     With the MIPI OST protocol driver,                                   are:
>
>> +# mkdir /sys/kernel/config/stp-policy/stm0:p_ost.policy/default
>> +# ls /sys/kernel/config/stp-policy/stm0:p_ost.policy/default
>> +channels  entity    masters
>> +
>> +The entity here is the set the entity that p_ost supports. Currently
>                     is the set of {entities | features} that p_ost supports. Currently
>
>> +p_ost supports ftrace, console and diag entity.
>                                             entities.
>
>> +
>> +Set entity:
>> +# echo 'ftrace' > /sys/kernel/config/stp-policy/stm0:p_ost.policy/default/entity
>> +
>> +Get available and currently selected (shown in square brackets) entity that p_ost supports:
>> +# cat /sys/kernel/config/stp-policy/stm0:p_ost.policy/default/entity
>> +[ftrace] console diag
>> +
>> +See Documentation/ABI/testing/configfs-stp-policy-p_ost for more details.

Thanks, will update.

Yingchao