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linux-stable/Documentation/ABI/testing/sysfs-class-stm

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stm class: Introduce an abstraction for System Trace Module devices 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>
2015-09-22 12:47:10 +00:00
What: /sys/class/stm/<stm>/masters
Date: June 2015
KernelVersion: 4.3
Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Description:
Shows first and last available to software master numbers on
this STM device.
What: /sys/class/stm/<stm>/channels
Date: June 2015
KernelVersion: 4.3
Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Description:
Shows the number of channels per master on this STM device.
stm class: Support devices that override software assigned masters Some STM devices adjust software assigned master numbers depending on the trace source and its runtime state and whatnot. This patch adds a sysfs attribute to inform the trace-side software that master numbers assigned to software sources will not match those in the STP stream, so that, for example, master/channel allocation policy can be adjusted accordingly. Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-03 17:33:37 +00:00
What: /sys/class/stm/<stm>/hw_override
Date: March 2016
KernelVersion: 4.7
Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Description:
Reads as 0 if master numbers in the STP stream produced by
this stm device will match the master numbers assigned by
the software or 1 if the stm hardware overrides software
assigned masters.