diff options
| -rw-r--r-- | OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c | 95 |
1 files changed, 71 insertions, 24 deletions
diff --git a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c index 467cb27..4ccb38d 100644 --- a/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c +++ b/OvmfPkg/Library/XenConsoleSerialPortLib/XenConsoleSerialPortLib.c @@ -25,6 +25,17 @@ #include <IndustryStandard/Xen/event_channel.h>
//
+// We can't use DebugLib due to a constructor dependency cycle between DebugLib
+// and ourselves.
+//
+#define ASSERT(Expression) \
+ do { \
+ if (!(Expression)) { \
+ CpuDeadLoop (); \
+ } \
+ } while (FALSE)
+
+//
// The code below expects these global variables to be mutable, even in the case
// that we have been incorporated into SEC or PEIM phase modules (which is
// allowed by our INF description). While this is a dangerous assumption to make
@@ -34,6 +45,17 @@ STATIC evtchn_send_t mXenConsoleEventChain;
STATIC struct xencons_interface *mXenConsoleInterface;
+/**
+ Initialize the serial device hardware.
+
+ If no initialization is required, then return RETURN_SUCCESS.
+ If the serial device was successfully initialized, then return RETURN_SUCCESS.
+ If the serial device could not be initialized, then return RETURN_DEVICE_ERROR.
+
+ @retval RETURN_SUCCESS The serial device was initialized.
+ @retval RETURN_DEVICE_ERROR The serial device could not be initialized.
+
+**/
RETURN_STATUS
EFIAPI
SerialPortInitialize (
@@ -41,7 +63,7 @@ SerialPortInitialize ( )
{
if (! XenHypercallIsAvailable ()) {
- return RETURN_NOT_FOUND;
+ return RETURN_DEVICE_ERROR;
}
if (!mXenConsoleInterface) {
@@ -57,13 +79,20 @@ SerialPortInitialize ( }
/**
- Write data to serial device.
+ Write data from buffer to serial device.
+
+ Writes NumberOfBytes data bytes from Buffer to the serial device.
+ The number of bytes actually written to the serial device is returned.
+ If the return value is less than NumberOfBytes, then the write operation failed.
+ If Buffer is NULL, then ASSERT().
+ If NumberOfBytes is zero, then return 0.
- @param Buffer Point of data buffer which need to be written.
- @param NumberOfBytes Number of output bytes which are cached in Buffer.
+ @param Buffer Pointer to the data buffer to be written.
+ @param NumberOfBytes Number of bytes to written to the serial device.
- @retval 0 Write data failed.
- @retval !0 Actual number of bytes written to serial device.
+ @retval 0 NumberOfBytes is 0.
+ @retval >0 The number of bytes written to the serial device.
+ If this value is less than NumberOfBytes, then the write operation failed.
**/
UINTN
@@ -76,38 +105,50 @@ SerialPortWrite ( XENCONS_RING_IDX Consumer, Producer;
UINTN Sent;
+ ASSERT (Buffer != NULL);
+
+ if (NumberOfBytes == 0) {
+ return 0;
+ }
+
if (!mXenConsoleInterface) {
return 0;
}
- Consumer = mXenConsoleInterface->out_cons;
- Producer = mXenConsoleInterface->out_prod;
+ Sent = 0;
+ do {
+ Consumer = mXenConsoleInterface->out_cons;
+ Producer = mXenConsoleInterface->out_prod;
- MemoryFence ();
+ MemoryFence ();
- Sent = 0;
- while (Sent < NumberOfBytes && ((Producer - Consumer) < sizeof (mXenConsoleInterface->out)))
- mXenConsoleInterface->out[MASK_XENCONS_IDX(Producer++, mXenConsoleInterface->out)] = Buffer[Sent++];
+ while (Sent < NumberOfBytes && ((Producer - Consumer) < sizeof (mXenConsoleInterface->out)))
+ mXenConsoleInterface->out[MASK_XENCONS_IDX(Producer++, mXenConsoleInterface->out)] = Buffer[Sent++];
- MemoryFence ();
+ MemoryFence ();
- mXenConsoleInterface->out_prod = Producer;
+ mXenConsoleInterface->out_prod = Producer;
- if (Sent > 0) {
XenHypercallEventChannelOp (EVTCHNOP_send, &mXenConsoleEventChain);
- }
+
+ } while (Sent < NumberOfBytes);
return Sent;
}
/**
- Read data from serial device and save the data in buffer.
+ Read data from serial device and save the datas in buffer.
+
+ Reads NumberOfBytes data bytes from a serial device into the buffer
+ specified by Buffer. The number of bytes actually read is returned.
+ If Buffer is NULL, then ASSERT().
+ If NumberOfBytes is zero, then return 0.
- @param Buffer Point of data buffer which need to be written.
- @param NumberOfBytes Size of Buffer[].
+ @param Buffer Pointer to the data buffer to store the data read from the serial device.
+ @param NumberOfBytes Number of bytes which will be read.
- @retval 0 Read data failed.
- @retval !0 Actual number of bytes read from serial device.
+ @retval 0 Read data failed, no data is to be read.
+ @retval >0 Actual number of bytes read from serial device.
**/
UINTN
@@ -120,6 +161,12 @@ SerialPortRead ( XENCONS_RING_IDX Consumer, Producer;
UINTN Received;
+ ASSERT (Buffer != NULL);
+
+ if (NumberOfBytes == 0) {
+ return 0;
+ }
+
if (!mXenConsoleInterface) {
return 0;
}
@@ -143,10 +190,10 @@ SerialPortRead ( }
/**
- Check to see if any data is available to be read from the debug device.
+ Polls a serial device to see if there is any data waiting to be read.
- @retval TRUE At least one byte of data is available to be read
- @retval FALSE No data is available to be read
+ @retval TRUE Data is waiting to be read from the serial device.
+ @retval FALSE There is no data waiting to be read from the serial device.
**/
BOOLEAN
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