[PATCH 2/4] hw/ide/core: Clear LBA and drive bits for EXECUTE DEVICE DIAGNOSTIC

[Lev Kujawski]

Prior to this patch, cmd_exec_dev_diagnostic relied upon
ide_set_signature to clear the device register.  While the
preservation of the drive bit by ide_set_signature is necessary for
the DEVICE RESET, IDENTIFY DEVICE, and READ SECTOR commands,
ATA/ATAPI-6 specifies that "DEV shall be cleared to zero" for EXECUTE
DEVICE DIAGNOSTIC.

This deviation was uncovered by the ATACT Device Testing Program
written by Hale Landis.

Signed-off-by: Lev Kujawski <lkujaw@member.fsf.org>
---
 hw/ide/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/ide/core.c b/hw/ide/core.c
index c2caa54285..5a24547e49 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -1704,8 +1704,14 @@ static bool cmd_identify_packet(IDEState *s, uint8_t cmd)
     return false;
 }
 
+/* EXECUTE DEVICE DIAGNOSTIC */
 static bool cmd_exec_dev_diagnostic(IDEState *s, uint8_t cmd)
 {
+    /*
+     * Clear the device register per the ATA (v6) specification,
+     * because ide_set_signature does not clear LBA or drive bits.
+     */
+    s->select = (ATA_DEV_ALWAYS_ON);
     ide_set_signature(s);
 
     if (s->drive_kind == IDE_CD) {
-- 
2.34.1