[PATCH 6/6] tuna: Add centralized input validation for CPU numbers and RT priorities

[John Kacur <jkacur@redhat.com>]

Add a validation block in main() that validates converted arguments before
command dispatch. This provides early detection of invalid inputs with
clear, user-friendly error messages.

CPU number validation:
- Validates that all CPU numbers in cpu_list are within valid range
  (0 to nr_cpus-1)
- Applies to commands: move, spread, isolate, include, run, save,
  show_threads, show_irqs, gui, cpu_power
- Error message shows invalid CPUs and system's valid range

RT priority validation:
- Validates that RT priorities are within valid range (1-99)
- Applies to commands: priority, run
- Validates both POLICY:RTPRIO format and priority-only format
- Only validates when a policy is specified or priority is non-zero

Old behavior with invalid inputs:
- Invalid CPU: Either silent failure (show_threads) or confusing
  tracebacks (move, isolate)
- Invalid RT priority: Generic "Invalid argument" errno message

New behavior:
- Clear error message (e.g., "tuna: Invalid CPU numbers: [999].
  System has 16 CPUs (0-15)")
- Fails fast before attempting operations
- No verbose usage output, just the concise error

Benefits:
- Better user experience with clear error messages
- Centralized validation logic (easier to maintain)
- Prevents confusing error messages from system calls

This completes task #6 from the argparse enhancements tracking document.

Assisted-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: John Kacur <jkacur@redhat.com>
---
 tuna-cmd.py | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/tuna-cmd.py b/tuna-cmd.py
index f1605896c33c..b9a071414125 100755
--- a/tuna-cmd.py
+++ b/tuna-cmd.py
@@ -852,6 +852,32 @@ def main():
             if 'irq_list' in vars(args) and isinstance(args.irq_list, list) and not args.irq_list:
                 print("[WARNING] IRQ pattern matched 0 IRQs", file=sys.stderr)
 
+    # Validate converted arguments
+    if args.command in ['move', 'm', 'spread', 'x', 'isolate', 'i', 'include', 'I', 'run', 'r', 'save', 's', 'show_threads', 'show_irqs', 'gui', 'g', 'cpu_power']:
+        if 'cpu_list' in vars(args) and args.cpu_list:
+            nr_cpus = utils.get_nr_cpus()
+            invalid_cpus = [c for c in args.cpu_list if c >= nr_cpus]
+            if invalid_cpus:
+                print(f"[ERROR] Invalid CPU numbers: {invalid_cpus}. System has {nr_cpus} CPUs (0-{nr_cpus-1})", file=sys.stderr)
+                sys.exit(2)
+
+    if args.command in ['priority', 'p', 'run', 'r']:
+        if 'priority' in vars(args) and args.priority:
+            policy, rtprio = args.priority
+            # Only validate rtprio if a policy was specified or if rtprio is non-zero
+            if policy is not None or rtprio != 0:
+                # RT policies (FIFO, RR) require priority 1-99
+                # SCHED_FIFO = 1, SCHED_RR = 2 in Linux
+                if policy in (1, 2) and rtprio is not None:
+                    if rtprio < 1 or rtprio > 99:
+                        print(f"[ERROR] Invalid RT priority: {rtprio}. RT priorities must be 1-99", file=sys.stderr)
+                        sys.exit(2)
+                # If only priority specified (no policy), assume RT and validate
+                elif policy is None and rtprio != 0:
+                    if rtprio < 1 or rtprio > 99:
+                        print(f"[ERROR] Invalid RT priority: {rtprio}. RT priorities must be 1-99", file=sys.stderr)
+                        sys.exit(2)
+
     # if args.command in ['apply', 'a']:
     #     apply_config(args.profilename)
 
-- 
2.54.0