[PATCH 1/5] hwlatdetect: Make count field backward compatible

[John Kacur <jkacur@redhat.com>]

The count field was added to hwlat trace output in kernel v5.10
(commit b396bfdebffc). Make this field optional to maintain backward
compatibility with older kernels:

- Set count to None when the field is not present in trace output
- Only include count in __str__ output when it exists
- Fall back to len(samples) in get("count") for older kernels

This allows hwlatdetect to work correctly on both kernels with and
without the count field.

Assisted-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: John Kacur <jkacur@redhat.com>
---
 src/hwlatdetect/hwlatdetect.py | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/hwlatdetect/hwlatdetect.py b/src/hwlatdetect/hwlatdetect.py
index af9852cc95e8..c128f60bc8db 100755
--- a/src/hwlatdetect/hwlatdetect.py
+++ b/src/hwlatdetect/hwlatdetect.py
@@ -264,10 +264,12 @@ class Tracer(Detector):
             self.timestamp = str(ts)
             self.inner = int(i)
             self.outer = int(o)
-            self.count = int(kv["count"])
+            self.count = int(kv["count"]) if "count" in kv else None
 
         def __str__(self):
-            return f"ts: {self.timestamp}, inner:{self.inner}, outer:{self.outer}, cpu:{self.cpu}, count:{self.count}"
+            if self.count is not None:
+                return f"ts: {self.timestamp}, inner:{self.inner}, outer:{self.outer}, cpu:{self.cpu}, count:{self.count}"
+            return f"ts: {self.timestamp}, inner:{self.inner}, outer:{self.outer}, cpu:{self.cpu}"
 
         def display(self):
             """ convert object to string and print """
@@ -299,7 +301,10 @@ class Tracer(Detector):
 
     def get(self, field):
         if field == "count":
-            return sum(s.count for s in self.samples)
+            # Use new count field if available, otherwise fall back to sample count
+            if self.samples and self.samples[0].count is not None:
+                return sum(s.count for s in self.samples)
+            return len(self.samples)
         if field == "max":
             max = 0
             for values in self.samples:
-- 
2.53.0