From 0c7515e1c47372ae5d53f2e281b2ccd425ebbcc6 Mon Sep 17 00:00:00 2001
From: John Snow <jsnow@redhat.com>
Date: Fri, 24 Jul 2020 01:22:58 -0400
Subject: ide: remove magic constants from the device register

(In QEMU, we call this the "select" register.)

My memory isn't good enough to memorize what these magic runes
do. Label them to prevent mixups from happening in the future.

Side note: I assume it's safe to always set 0xA0 even though ATA2 claims
these bits are reserved, because ATA3 immediately reinstated that these
bits should be always on. ATA4 and subsequent specs only claim that the
fields are obsolete, so I assume it's safe to leave these set and that
it should work with the widest array of guests.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 hw/ide/core.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

(limited to 'hw/ide')

diff --git a/hw/ide/core.c b/hw/ide/core.c
index afff355e5c..8a55352e4b 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -367,7 +367,7 @@ fill_buffer:
 
 static void ide_set_signature(IDEState *s)
 {
-    s->select &= 0xf0; /* clear head */
+    s->select &= ~(ATA_DEV_HS); /* clear head */
     /* put signature */
     s->nsector = 1;
     s->sector = 1;
@@ -586,7 +586,7 @@ void ide_transfer_stop(IDEState *s)
 int64_t ide_get_sector(IDEState *s)
 {
     int64_t sector_num;
-    if (s->select & 0x40) {
+    if (s->select & (ATA_DEV_LBA)) {
         if (s->lba48) {
             sector_num = ((int64_t)s->hob_hcyl << 40) |
                 ((int64_t) s->hob_lcyl << 32) |
@@ -595,13 +595,13 @@ int64_t ide_get_sector(IDEState *s)
                 ((int64_t) s->lcyl << 8) | s->sector;
         } else {
             /* LBA28 */
-            sector_num = ((s->select & 0x0f) << 24) | (s->hcyl << 16) |
-                (s->lcyl << 8) | s->sector;
+            sector_num = ((s->select & (ATA_DEV_LBA_MSB)) << 24) |
+                (s->hcyl << 16) | (s->lcyl << 8) | s->sector;
         }
     } else {
         /* CHS */
         sector_num = ((s->hcyl << 8) | s->lcyl) * s->heads * s->sectors +
-            (s->select & 0x0f) * s->sectors + (s->sector - 1);
+            (s->select & (ATA_DEV_HS)) * s->sectors + (s->sector - 1);
     }
 
     return sector_num;
@@ -610,7 +610,7 @@ int64_t ide_get_sector(IDEState *s)
 void ide_set_sector(IDEState *s, int64_t sector_num)
 {
     unsigned int cyl, r;
-    if (s->select & 0x40) {
+    if (s->select & (ATA_DEV_LBA)) {
         if (s->lba48) {
             s->sector = sector_num;
             s->lcyl = sector_num >> 8;
@@ -620,7 +620,8 @@ void ide_set_sector(IDEState *s, int64_t sector_num)
             s->hob_hcyl = sector_num >> 40;
         } else {
             /* LBA28 */
-            s->select = (s->select & 0xf0) | (sector_num >> 24);
+            s->select = (s->select & ~(ATA_DEV_LBA_MSB)) |
+                ((sector_num >> 24) & (ATA_DEV_LBA_MSB));
             s->hcyl = (sector_num >> 16);
             s->lcyl = (sector_num >> 8);
             s->sector = (sector_num);
@@ -631,7 +632,8 @@ void ide_set_sector(IDEState *s, int64_t sector_num)
         r = sector_num % (s->heads * s->sectors);
         s->hcyl = cyl >> 8;
         s->lcyl = cyl;
-        s->select = (s->select & 0xf0) | ((r / s->sectors) & 0x0f);
+        s->select = (s->select & ~(ATA_DEV_HS)) |
+            ((r / s->sectors) & (ATA_DEV_HS));
         s->sector = (r % s->sectors) + 1;
     }
 }
@@ -1302,10 +1304,10 @@ void ide_ioport_write(void *opaque, uint32_t addr, uint32_t val)
         break;
     case ATA_IOPORT_WR_DEVICE_HEAD:
         ide_clear_hob(bus);
-        bus->ifs[0].select = val | 0xa0;
-        bus->ifs[1].select = val | 0xa0;
+        bus->ifs[0].select = val | (ATA_DEV_ALWAYS_ON);
+        bus->ifs[1].select = val | (ATA_DEV_ALWAYS_ON);
         /* select drive */
-        bus->unit = (val >> 4) & 1;
+        bus->unit = (val & (ATA_DEV_SELECT)) ? 1 : 0;
         break;
     default:
     case ATA_IOPORT_WR_COMMAND:
@@ -1343,7 +1345,7 @@ static void ide_reset(IDEState *s)
     s->hob_lcyl = 0;
     s->hob_hcyl = 0;
 
-    s->select = 0xa0;
+    s->select = (ATA_DEV_ALWAYS_ON);
     s->status = READY_STAT | SEEK_STAT;
 
     s->lba48 = 0;
-- 
cgit v1.2.3