i2c:smbus: Correct the working of quick commands

The logic of handling quick SMBus commands was wrong.  If you get a
finish event with no data, that's a quick command.

Document the quick command while we are at it.

Signed-off-by: Corey Minyard <cminyard@mvista.com>

diff --git a/hw/i2c/smbus_slave.c b/hw/i2c/smbus_slave.c
index 6e4d542f51abbfe31c1f410256df9a268aedfee4..6a89a286e3d2db35254ffaeb77f4242332deb839 100644 (file)
--- a/hw/i2c/smbus_slave.c
+++ b/hw/i2c/smbus_slave.c
@@ -54,9 +54,7 @@ static void smbus_do_write(SMBusDevice *dev)
 {
     SMBusDeviceClass *sc = SMBUS_DEVICE_GET_CLASS(dev);
 
-    if (dev->data_len == 0) {
-        smbus_do_quick_cmd(dev, 0);
-    } else if (dev->data_len == 1) {
+    if (dev->data_len == 1) {
         DPRINTF("Send Byte\n");
         if (sc->send_byte) {
             sc->send_byte(dev, dev->data_buf[0]);
@@ -120,19 +118,24 @@ static int smbus_i2c_event(I2CSlave *s, enum i2c_event event)
         break;
 
     case I2C_FINISH:
-        switch (dev->mode) {
-        case SMBUS_WRITE_DATA:
-            smbus_do_write(dev);
-            break;
-        case SMBUS_RECV_BYTE:
-            smbus_do_quick_cmd(dev, 1);
-            break;
-        case SMBUS_READ_DATA:
-            BADF("Unexpected stop during receive\n");
-            break;
-        default:
-            /* Nothing to do.  */
-            break;
+        if (dev->data_len == 0) {
+            if (dev->mode == SMBUS_WRITE_DATA || dev->mode == SMBUS_READ_DATA) {
+                smbus_do_quick_cmd(dev, dev->mode == SMBUS_READ_DATA);
+            }
+        } else {
+            switch (dev->mode) {
+            case SMBUS_WRITE_DATA:
+                smbus_do_write(dev);
+                break;
+
+            case SMBUS_READ_DATA:
+                BADF("Unexpected stop during receive\n");
+                break;
+
+            default:
+                /* Nothing to do.  */
+                break;
+            }
         }
         dev->mode = SMBUS_IDLE;
         dev->data_len = 0;

diff --git a/include/hw/i2c/smbus_slave.h b/include/hw/i2c/smbus_slave.h
index 46b8948f0f3f6526d688fcf6e4b379abb43b7ee7..5ef1c72ad0a0535ed094698c1a52c1140086f31f 100644 (file)
--- a/include/hw/i2c/smbus_slave.h
+++ b/include/hw/i2c/smbus_slave.h
@@ -40,6 +40,11 @@ typedef struct SMBusDevice SMBusDevice;
 typedef struct SMBusDeviceClass
 {
     I2CSlaveClass parent_class;
+
+    /*
+     * An operation with no data, special in SMBus.
+     * This may be NULL, quick commands are ignore in that case.
+     */
     void (*quick_cmd)(SMBusDevice *dev, uint8_t read);
     void (*send_byte)(SMBusDevice *dev, uint8_t val);
     uint8_t (*receive_byte)(SMBusDevice *dev);