coresight: Expose device connections via sysfs

Coresight device connections are a bit complicated and is not
exposed currently to the user. One has to look at the platform
descriptions (DT bindings or ACPI bindings) to make an understanding.
Given the new naming scheme, it will be helpful to have this information
to choose the appropriate devices for tracing. This patch exposes
the device connections via links in the sysfs directories.

e.g, for a connection devA[OutputPort_X] -> devB[InputPort_Y]
is represented as two symlinks:

  /sys/bus/coresight/.../devA/out:X -> /sys/bus/coresight/.../devB
  /sys/bus/coresight/.../devB/in:Y  -> /sys/bus/coresight/.../devA

Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[Revised to use the generic sysfs links functions & link structures.
Provides a connections sysfs group in each device to hold the links.]
Co-developed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200518180242.7916-5-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Suzuki K Poulose 2020-05-18 12:02:23 -06:00 • committed by Greg Kroah-Hartman
commit 8a7365c2d4
4 changed files with 121 additions and 12 deletions