Add fix command and troubleshooting for errno=16 error

- Add 'fix' command to diagnose CEC connection issues
- Add detailed troubleshooting section for common errors
- Fix handles errno=16 (device busy) by checking processes and trying sudo
- Document solutions for CEC permission and connection issues

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -37,6 +37,7 @@ chmod +x cec-control.sh
 | `scan` | Scan for CEC devices | `./cec-control.sh scan` |
 | `status` | Show CEC adapter status | `./cec-control.sh status` |
 | `info` | Show TV information | `./cec-control.sh info` |
+| `fix` | Troubleshoot connection issues | `./cec-control.sh fix` |
 | `raw <command>` | Send raw CEC command | `./cec-control.sh raw 4f:82:10:00` |
 | `help` | Show help message | `./cec-control.sh help` |
 
@@ -55,9 +56,48 @@ chmod +x cec-control.sh
 
 ## Troubleshooting
 
-- **CEC not working**: Make sure CEC is enabled in your TV settings
-- **Permission denied**: Run with `sudo` if needed
-- **Device not found**: Check HDMI connection and try rescanning with `scan` command
+### Common Issues
+
+**ioctl CEC_S_MODE failed - errno=16 (Device or resource busy)**
+
+This error means something else is using the CEC device. Try these solutions:
+
+1. Run the built-in fix command:
+```bash
+./cec-control.sh fix
+```
+
+2. Kill any existing CEC processes:
+```bash
+sudo killall cec-client
+```
+
+3. Check what's using the device:
+```bash
+sudo lsof /dev/cec0
+```
+
+4. Try running with sudo:
+```bash
+sudo ./cec-control.sh scan
+```
+
+5. If using Kodi or LibreELEC, CEC may be enabled in the application. Disable it or stop the application first.
+
+**CEC not working**
+- Make sure CEC is enabled in your TV settings (often called "HDMI Control", "CEC Control", or branded names like "Bravia Link", "Anynet+", etc.)
+- Try a different HDMI port on your TV
+- Check that the HDMI cable is properly connected
+
+**Permission denied**
+- Add your user to the `video` group: `sudo usermod -aG video $USER`
+- Then log out and back in
+- Or run with `sudo`
+
+**Device not found**
+- Check if `/dev/cec0` exists: `ls -l /dev/cec0`
+- Ensure `cec-utils` is installed
+- Try rebooting the Pi
 
 ## Advanced Usage