i2c: pm_smbus: Make the I2C block read command read-only

It did have write capability, but the manual says the behavior
with write enabled is undefined.  So just set an error in this
case.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1534796770-10295-4-git-send-email-minyard@acm.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/i2c/pm_smbus.c

@@ -55,7 +55,7 @@
 #define PROT_WORD_DATA      3
 #define PROT_PROC_CALL      4
 #define PROT_BLOCK_DATA     5
-#define PROT_I2C_BLOCK_DATA 6
+#define PROT_I2C_BLOCK_READ 6
 
 /*#define DEBUG*/
 
@@ -115,7 +115,7 @@ static void smb_transaction(PMSMBus *s)
             goto done;
         }
         break;
-    case PROT_I2C_BLOCK_DATA:
+    case PROT_I2C_BLOCK_READ:
         if (read) {
             int xfersize = s->smb_data0;
             if (xfersize > sizeof(s->smb_data)) {
@@ -125,9 +125,8 @@ static void smb_transaction(PMSMBus *s)
                                    xfersize, false, true);
             goto data8;
         } else {
-            ret = smbus_write_block(bus, addr, cmd, s->smb_data, s->smb_data0,
-                                    false);
-            goto done;
+            /* The manual says the behavior is undefined, just set DEV_ERR. */
+            goto error;
         }
         break;
     default: