From ff800af820e9ff5d1cd6cc148dda98e8947dc348 Mon Sep 17 00:00:00 2001
From: Sebastian Sumpf <sebastian.sumpf@genode-labs.com>
Date: Sun, 17 Sep 2017 11:15:26 +0200
Subject: [PATCH] ahci: make port enumeration independent from port count

fixes #2522
---
 repos/os/src/drivers/ahci/ahci.cc | 34 ++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/repos/os/src/drivers/ahci/ahci.cc b/repos/os/src/drivers/ahci/ahci.cc
index 598c978a2..467f6fd3d 100644
--- a/repos/os/src/drivers/ahci/ahci.cc
+++ b/repos/os/src/drivers/ahci/ahci.cc
@@ -95,6 +95,19 @@ struct Ahci
 		platform_hba.ack_irq();
 	}
 
+	/*
+	 * Least significant bit
+	 */
+	unsigned lsb(unsigned bits) const
+	{
+		for (unsigned i = 0; i < 32; i++)
+			if (bits & (1u << i)) {
+				return i;
+			}
+
+		return 0;
+	}
+
 	void info()
 	{
 		using Genode::log;
@@ -116,38 +129,39 @@ struct Ahci
 		for (unsigned i = 0; i < hba.port_count(); i++) {
 
 			/* check if port is implemented */
-			if (!(available & (1U << i)))
-				continue;
+			if (!available) break;
+			unsigned index = lsb(available);
+			available ^= (1u << index);
 
 			bool enabled = false;
 
-			switch (Port_base(i, hba).read<Port_base::Sig>()) {
+			switch (Port_base(index, hba).read<Port_base::Sig>()) {
 				case ATA_SIG:
 					try {
-						ports[i] = new (&alloc)
+						ports[index] = new (&alloc)
 							Ata_driver(alloc, ram, root, ready_count, rm, hba,
-							           platform_hba, i, device_identified);
+							           platform_hba, index, device_identified);
 						enabled = true;
 					} catch (...) { }
 
-					log("\t\t#", i, ":", enabled ? " ATA" : " off (ATA)");
+					log("\t\t#", index, ":", enabled ? " ATA" : " off (ATA)");
 					break;
 
 				case ATAPI_SIG:
 				case ATAPI_SIG_QEMU:
 					if (enable_atapi)
 						try {
-							ports[i] = new (&alloc)
+							ports[index] = new (&alloc)
 								Atapi_driver(ram, root, ready_count, rm, hba,
-								             platform_hba, i);
+								             platform_hba, index);
 							enabled = true;
 						} catch (...) { }
 
-					log("\t\t#", i, ":", enabled ? " ATAPI" : " off (ATAPI)");
+					log("\t\t#", index, ":", enabled ? " ATAPI" : " off (ATAPI)");
 					break;
 
 				default:
-					log("\t\t#", i, ": off (unknown device signature)");
+					log("\t\t#", index, ": off (unknown device signature)");
 			}
 		}
 	};