hw/i2c: pmbus: add VCAP register

VCAP is a register for devices with energy storage capacitors.

Reviewed-by: Benjamin Streb <bstreb@google.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Titus Rwantare <titusr@google.com>
Message-ID: <20231023-staging-pmbus-v3-v4-4-07a8cb7cd20a@google.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/i2c/pmbus_device.c

@@ -906,6 +906,14 @@ static uint8_t pmbus_receive_byte(SMBusDevice *smd)
         }
         break;
 
+    case PMBUS_READ_VCAP:                 /* Read-Only word */
+        if (pmdev->pages[index].page_flags & PB_HAS_VCAP) {
+            pmbus_send16(pmdev, pmdev->pages[index].read_vcap);
+        } else {
+            goto passthough;
+        }
+        break;
+
     case PMBUS_READ_VOUT:                 /* Read-Only word */
         if (pmdev->pages[index].page_flags & PB_HAS_VOUT) {
             pmbus_send16(pmdev, pmdev->pages[index].read_vout);

include/hw/i2c/pmbus_device.h

@@ -243,6 +243,7 @@ OBJECT_DECLARE_TYPE(PMBusDevice, PMBusDeviceClass,
 #define PB_HAS_VIN_RATING          BIT_ULL(13)
 #define PB_HAS_VOUT_RATING         BIT_ULL(14)
 #define PB_HAS_VOUT_MODE           BIT_ULL(15)
+#define PB_HAS_VCAP                BIT_ULL(16)
 #define PB_HAS_IOUT                BIT_ULL(21)
 #define PB_HAS_IIN                 BIT_ULL(22)
 #define PB_HAS_IOUT_RATING         BIT_ULL(23)