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A System Trace Module (STM) is a device exporting data in System Trace Protocol (STP) format as defined by MIPI STP standards. Examples of such devices are Intel(R) Trace Hub and Coresight STM. This abstraction provides a unified interface for software trace sources to send their data over an STM device to a debug host. In order to do that, such a trace source needs to be assigned a pair of master/channel identifiers that all the data from this source will be tagged with. The STP decoder on the debug host side will use these master/channel tags to distinguish different trace streams from one another inside one STP stream. This abstraction provides a configfs-based policy management mechanism for dynamic allocation of these master/channel pairs based on trace source-supplied string identifier. It has the flexibility of being defined at runtime and at the same time (provided that the policy definition is aligned with the decoding end) consistency. For userspace trace sources, this abstraction provides write()-based and mmap()-based (if the underlying stm device allows this) output mechanism. For kernel-side trace sources, we provide "stm_source" device class that can be connected to an stm device at run time. Cc: linux-api@vger.kernel.org Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
12 lines
530 B
Plaintext
12 lines
530 B
Plaintext
What: /sys/class/stm_source/<stm_source>/stm_source_link
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Date: June 2015
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KernelVersion: 4.3
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Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
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Description:
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stm_source device linkage to stm device, where its tracing data
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is directed. Reads return an existing connection or "<none>" if
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this stm_source is not connected to any stm device yet.
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Write an existing (registered) stm device's name here to
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connect that device. If a device is already connected to this
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stm_source, it will first be disconnected.
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