hw/i2c: add asynchronous send

Add an asynchronous version of i2c_send() that requires the slave to
explicitly acknowledge on the bus with i2c_ack().

The current master must use the new i2c_start_send_async() to indicate
that it wants to do an asynchronous transfer. This allows the i2c core
to check if the target slave supports this or not. This approach relies
on adding a new enum i2c_event member, which is why a bunch of other
devices needs changes in their event handling switches.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Message-Id: <20220601210831.67259-5-its@irrelevant.dk>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220630045133.32251-6-me@pjd.dev>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

hw/arm/pxa2xx.c

@@ -1305,6 +1305,8 @@ static int pxa2xx_i2c_event(I2CSlave *i2c, enum i2c_event event)
     case I2C_NACK:
         s->status |= 1 << 1;				/* set ACKNAK */
         break;
+    default:
+        return -1;
     }
     pxa2xx_i2c_update(s);
 

hw/display/sii9022.c

@@ -76,6 +76,8 @@ static int sii9022_event(I2CSlave *i2c, enum i2c_event event)
         break;
     case I2C_NACK:
         break;
+    default:
+        return -1;
     }
 
     return 0;

hw/display/ssd0303.c

@@ -196,6 +196,8 @@ static int ssd0303_event(I2CSlave *i2c, enum i2c_event event)
     case I2C_NACK:
         /* Nothing to do.  */
         break;
+    default:
+        return -1;
     }
 
     return 0;

hw/i2c/core.c

@@ -161,7 +161,8 @@ static int i2c_do_start_transfer(I2CBus *bus, uint8_t address,
            start condition.  */
 
         if (sc->event) {
-            trace_i2c_event("start", s->address);
+            trace_i2c_event(event == I2C_START_SEND ? "start" : "start_async",
+                            s->address);
             rv = sc->event(s, event);
             if (rv && !bus->broadcast) {
                 if (bus_scanned) {
@@ -212,6 +213,11 @@ int i2c_start_send(I2CBus *bus, uint8_t address)
     return i2c_do_start_transfer(bus, address, I2C_START_SEND);
 }
 
+int i2c_start_send_async(I2CBus *bus, uint8_t address)
+{
+    return i2c_do_start_transfer(bus, address, I2C_START_SEND_ASYNC);
+}
+
 void i2c_end_transfer(I2CBus *bus)
 {
     I2CSlaveClass *sc;
@@ -261,6 +267,23 @@ int i2c_send(I2CBus *bus, uint8_t data)
     return ret ? -1 : 0;
 }
 
+int i2c_send_async(I2CBus *bus, uint8_t data)
+{
+    I2CNode *node = QLIST_FIRST(&bus->current_devs);
+    I2CSlave *slave = node->elt;
+    I2CSlaveClass *sc = I2C_SLAVE_GET_CLASS(slave);
+
+    if (!sc->send_async) {
+        return -1;
+    }
+
+    trace_i2c_send_async(slave->address, data);
+
+    sc->send_async(slave, data);
+
+    return 0;
+}
+
 uint8_t i2c_recv(I2CBus *bus)
 {
     uint8_t data = 0xff;
@@ -297,6 +320,17 @@ void i2c_nack(I2CBus *bus)
     }
 }
 
+void i2c_ack(I2CBus *bus)
+{
+    if (!bus->bh) {
+        return;
+    }
+
+    trace_i2c_ack();
+
+    qemu_bh_schedule(bus->bh);
+}
+
 static int i2c_slave_post_load(void *opaque, int version_id)
 {
     I2CSlave *dev = opaque;

hw/i2c/smbus_slave.c

@@ -143,6 +143,10 @@ static int smbus_i2c_event(I2CSlave *s, enum i2c_event event)
             dev->mode = SMBUS_CONFUSED;
             break;
         }
+        break;
+
+    default:
+        return -1;
     }
 
     return 0;

hw/i2c/trace-events

@@ -4,7 +4,9 @@
 
 i2c_event(const char *event, uint8_t address) "%s(addr:0x%02x)"
 i2c_send(uint8_t address, uint8_t data) "send(addr:0x%02x) data:0x%02x"
+i2c_send_async(uint8_t address, uint8_t data) "send_async(addr:0x%02x) data:0x%02x"
 i2c_recv(uint8_t address, uint8_t data) "recv(addr:0x%02x) data:0x%02x"
+i2c_ack(void) ""
 
 # aspeed_i2c.c
 

hw/nvram/eeprom_at24c.c

@@ -75,6 +75,8 @@ int at24c_eeprom_event(I2CSlave *s, enum i2c_event event)
         break;
     case I2C_NACK:
         break;
+    default:
+        return -1;
     }
     return 0;
 }

hw/sensor/lsm303dlhc_mag.c

@@ -427,6 +427,8 @@ static int lsm303dlhc_mag_event(I2CSlave *i2c, enum i2c_event event)
         break;
     case I2C_NACK:
         break;
+    default:
+        return -1;
     }
 
     s->len = 0;

include/hw/i2c/i2c.h

@@ -12,6 +12,7 @@
 enum i2c_event {
     I2C_START_RECV,
     I2C_START_SEND,
+    I2C_START_SEND_ASYNC,
     I2C_FINISH,
     I2C_NACK /* Masker NACKed a receive byte.  */
 };
@@ -28,6 +29,9 @@ struct I2CSlaveClass {
     /* Master to slave. Returns non-zero for a NAK, 0 for success. */
     int (*send)(I2CSlave *s, uint8_t data);
 
+    /* Master to slave (asynchronous). Receiving slave must call i2c_ack(). */
+    void (*send_async)(I2CSlave *s, uint8_t data);
+
     /*
      * Slave to master.  This cannot fail, the device should always
      * return something here.
@@ -127,11 +131,23 @@ int i2c_start_recv(I2CBus *bus, uint8_t address);
  */
 int i2c_start_send(I2CBus *bus, uint8_t address);
 
+/**
+ * i2c_start_send_async: start an asynchronous 'send' transfer on an I2C bus.
+ *
+ * @bus: #I2CBus to be used
+ * @address: address of the slave
+ *
+ * Return: 0 on success, -1 on error
+ */
+int i2c_start_send_async(I2CBus *bus, uint8_t address);
+
 void i2c_end_transfer(I2CBus *bus);
 void i2c_nack(I2CBus *bus);
+void i2c_ack(I2CBus *bus);
 void i2c_bus_master(I2CBus *bus, QEMUBH *bh);
 void i2c_bus_release(I2CBus *bus);
 int i2c_send(I2CBus *bus, uint8_t data);
+int i2c_send_async(I2CBus *bus, uint8_t data);
 uint8_t i2c_recv(I2CBus *bus);
 bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,
                   I2CNodeList *current_devs);