From f86bba3059c813bd6c28ec53c56760318d2ea653 Mon Sep 17 00:00:00 2001
From: Christian Helmuth <christian.helmuth@genode-labs.com>
Date: Fri, 12 Apr 2024 15:57:27 +0200
Subject: [PATCH] ps2: probe for working i8042

If no working controller is detected the driver just enters sleep
forever.

Issue #5174
---
 repos/os/src/drivers/ps2/x86/i8042.h | 39 +++++++++++++++++++---------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/repos/os/src/drivers/ps2/x86/i8042.h b/repos/os/src/drivers/ps2/x86/i8042.h
index 3105684d7f..315bedf7ca 100644
--- a/repos/os/src/drivers/ps2/x86/i8042.h
+++ b/repos/os/src/drivers/ps2/x86/i8042.h
@@ -16,6 +16,7 @@
 
 #include <platform_session/device.h>
 #include <os/ring_buffer.h>
+#include <base/sleep.h>
 
 #include "serial_interface.h"
 
@@ -219,6 +220,24 @@ class I8042
 		bool _input_buffer_full()  { return _status() & STAT_IBF; }
 		bool _aux_data_pending()   { return _status() & STAT_AUX_DATA; }
 
+		/**
+		 * Probe controller by flushing limited amount of available data
+		 *
+		 * If there's no controller we'll infinitely read 0xff from status
+		 * port.
+		 */
+		bool _probe_controller()
+		{
+			unsigned attempts = 32; /* artificial maximum controller buffer size */
+
+			while (_output_buffer_full() && attempts > 0) {
+				(void)_data();
+				attempts--;
+			}
+
+			return attempts > 0;
+		}
+
 		/**
 		 * Wait for data and read
 		 */
@@ -229,10 +248,8 @@ class I8042
 			while (!_output_buffer_full() && attempts > 0)
 				attempts--;
 
-			if (attempts == 0) {
-				Genode::error("no data available");
+			if (attempts == 0)
 				return RET_INVALID;
-			}
 
 			return _data();
 		}
@@ -273,14 +290,11 @@ class I8042
 			_kbd_interface(*this, false),
 			_aux_interface(*this, true)
 		{
-			reset();
-		}
+			if (!_probe_controller()) {
+				Genode::log("i8042: no controller detected");
+				Genode::sleep_forever();
+			}
 
-		/**
-		 * Test and initialize controller
-		 */
-		void reset()
-		{
 			unsigned char configuration;
 			unsigned char ret;
 
@@ -295,18 +309,19 @@ class I8042
 				_command(CMD_TEST);
 				if ((ret = _wait_data()) != RET_TEST_OK) {
 					Genode::log("i8042: self test failed (", Genode::Hex(ret), ")");
-					return;
+					Genode::sleep_forever();
 				}
 
 				_command(CMD_KBD_TEST);
 				if ((ret = _wait_data()) != RET_KBD_TEST_OK) {
 					Genode::log("i8042: kbd test failed (", Genode::Hex(ret), ")");
-					return;
+					Genode::sleep_forever();
 				}
 
 				_command(CMD_AUX_TEST);
 				if ((ret = _wait_data()) != RET_AUX_TEST_OK) {
 					Genode::log("I8042: aux test failed (", Genode::Hex(ret), ")");
+					/* don't sleep forever as keyboard may work */
 					return;
 				}