Changeset 2167

Timestamp:

06/19/12 05:10:51 (8 years ago)

Author:

jwoithe

Message:

Possibly address ticket #242. Libraw1394 2.1.0 will introduce a new raw1394_read_cycle_timer_and_clock() which permits a choice of the clock to use. If this function is available, use it in preference to raw1394_read_cycle_timer(). By using CLOCK_MONOTONIC_RAW we should avoid timing glitches induced by NTP.
This patch exploits weak linkage to permit ffado to compile and run against all versions libraw1394 regardless of which is present on the runtime system. Correct behaviour with pre-2.1.0 libraw1394 has been verified. Testing with libraw1394 2.1.0 (when it's released) will be needed to confirm that the logic of this patch works as expected.

Files:

• trunk/libffado/src/libieee1394/ieee1394service.cpp (modified) (4 diffs)
• trunk/libffado/src/libieee1394/ieee1394service.h (modified) (1 diff)

trunk/libffado/src/libieee1394/ieee1394service.cpp

@@ -47 +47 @@
-#include <iostream>
-#include <iomanip>
+
+// Permit linking against older libraw1394 which didn't include this
+// function.
+#ifdef __GNUC__
+  #ifdef __APPLE__
+  #define WEAK_ATTRIBUTE weak_import
+  #else
+  #define WEAK_ATTRIBUTE __weak__
+  #endif
+  int raw1394_read_cycle_timer_and_clock(raw1394handle_t handle,
+      u_int32_t *cycle_timer, u_int64_t *local_time, clockid_t clk_id)
+      __attribute__((WEAK_ATTRIBUTE));
+#endif
-
-using namespace std;
@@ -318 +331 @@
-    uint32_t cycle_timer;
-    uint64_t local_time;
+    m_have_read_ctr_and_clock = false;
-    err = raw1394_read_cycle_timer(m_util_handle, &cycle_timer, &local_time);
-    if(err) {
@@ -330 +344 @@
-        m_have_new_ctr_read = false;
-    } else {
-        debugOutput(DEBUG_LEVEL_VERBOSE, "This system supports the raw1394_read_cycle_timer call, using it.\n");
-        m_have_new_ctr_read = true;
+
+        // Only if raw1394_read_cycle_timer() is present is it worth even
+        // considering the option that raw1394_read_cycle_timer_and_clock()
+        // might be available.
+        if (raw1394_read_cycle_timer_and_clock != NULL) {
+            err = raw1394_read_cycle_timer_and_clock(m_util_handle, &cycle_timer, &local_time, CLOCK_MONOTONIC_RAW);
+            if (!err)
+                m_have_read_ctr_and_clock = true;
+        }
+
+        if (m_have_read_ctr_and_clock)
+            debugOutput(DEBUG_LEVEL_VERBOSE, "This system supports the raw1394_read_cycle_timer_and_clock call, using it.\n");
+        else {
+            debugOutput(DEBUG_LEVEL_VERBOSE, "This system supports the raw1394_read_cycle_timer call, using it.\n");
+            debugOutput(DEBUG_LEVEL_NORMAL, "The raw1394_read_cycle_timer_and_clock call is not available.\n");
+            debugOutput(DEBUG_LEVEL_NORMAL, "Fallback to raw1394_read_cycle_timer.\n");
+            debugOutput(DEBUG_LEVEL_NORMAL, "FFADO may be susceptible to NTP-induced clock discontinuities.\n");
+            debugOutput(DEBUG_LEVEL_NORMAL, "Upgrade libraw1394 to version 2.1.0 or later if this is an issue.\n");
+        }
-    }
-
@@ -504 +536 @@
-Ieee1394Service::readCycleTimerReg(uint32_t *cycle_timer, uint64_t *local_time)
-{
+    if (m_have_read_ctr_and_clock) {
+        int err;
+        err = raw1394_read_cycle_timer_and_clock(m_util_handle, cycle_timer, local_time, CLOCK_MONOTONIC_RAW);
+        if(err) {
+            debugWarning("raw1394_read_cycle_timer_and_clock: %s\n", strerror(err));
+            return false;
+        }
+        return true;
+    } else
-    if(m_have_new_ctr_read) {
-        int err;

trunk/libffado/src/libieee1394/ieee1394service.h

@@ -461 +461 @@
-    CycleTimerHelper*       m_pCTRHelper;
-    bool                    m_have_new_ctr_read;
+    bool                    m_have_read_ctr_and_clock;
-
-    bool            m_filterFCPResponse;