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 patc

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 <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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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. Exa

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: [email protected]
Reviewed-by: Mathieu Poirier <[email protected]>
Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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