[Bug 1856549] Re: qemu-4.2.0/hw/misc/mac_via.c: 2 * bad test ?

[Laurent Vivier]

I think VIA RTC access method has been implemented earlier (Classic Mac,
1984-1989) than the I2C specification, so I'm not sure we can/should
port this to an I2C bus.

Specs are (from Apple Macintosh Family Hardware Reference Chapter 2,
Classi Macitosh Processor and Control)

z0000001  Seconds register 0 (lowest-order byte)
z0000101  Seconds register 1
z0001001  Seconds register 2
z0001101  Seconds register 3 (highest-order byte)
00110001  Test register (write-only)
00110101  Write-Protect Register (write-only)
z010aa01  RAM address 100aa ($10-$13) (first 20 bytes only)
z1aaaa01  RAM address 0aaaa ($00-$0F) (first 20 bytes only)
z0111aaa  Extended memory designator and sector number
          (Macintohs 512K enhanced and Macintosh plus only)

For a read request, z=1, for a write z=0
The letter a indicates bits whose value depend on what parameter RAM byte you 
want to address

So I think the mask/values should be:

diff --git a/hw/misc/mac_via.c b/hw/misc/mac_via.c
index f3f130ad96cc..7402cf3f1ee8 100644
--- a/hw/misc/mac_via.c
+++ b/hw/misc/mac_via.c
@@ -414,7 +414,7 @@ static void via1_rtc_update(MacVIAState *m)
                     int addr = (m->data_out >> 2) & 0x03;
                     m->data_in = v1s->PRAM[addr];
                     m->data_in_cnt = 8;
-                } else if ((m->data_out & 0xf3) == 0xa1) {
+                } else if ((m->data_out & 0xc3) == 0xc1) {
                     /* PRAM address 0x00 -> 0x0f */
                     int addr = (m->data_out >> 2) & 0x0f;
                     m->data_in = v1s->PRAM[addr];
@@ -460,11 +460,11 @@ static void via1_rtc_update(MacVIAState *m)
                 } else if (m->cmd == 0x35) {
                     /* Write Protect register */
                     m->wprotect = m->data_out & 1;
-                } else if ((m->cmd & 0xf3) == 0xa1) {
+                } else if ((m->cmd & 0xf3) == 0x21) {
                     /* PRAM address 0x10 -> 0x13 */
                     int addr = (m->cmd >> 2) & 0x03;
                     v1s->PRAM[addr] = m->data_out;
-                } else if ((m->cmd & 0xf3) == 0xa1) {
+                } else if ((m->cmd & 0xc3) == 0x41) {
                     /* PRAM address 0x00 -> 0x0f */
                     int addr = (m->cmd >> 2) & 0x0f;
                     v1s->PRAM[addr] = m->data_out;

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https://bugs.launchpad.net/bugs/1856549

Title:
  qemu-4.2.0/hw/misc/mac_via.c: 2 * bad test ?

Status in QEMU:
  New

Bug description:
  1.

  qemu-4.2.0/hw/misc/mac_via.c:417:27: style: Expression is always false
  because 'else if' condition matches previous condition at line 412.
  [multiCondition]

                  } else if ((m->data_out & 0xf3) == 0xa1) {
  ...
                  } else if ((m->data_out & 0xf3) == 0xa1) {

  2.

  qemu-4.2.0/hw/misc/mac_via.c:467:27: style: Expression is always false
  because 'else if' condition matches previous condition at line 463.
  [multiCondition]

  Duplicate.

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