migrate from req_ctx to msgb

We now generalize the USB communiction and abandon the 'req_ctx'
structure inherited from openpcd.  Instead we use the libosmocore 'msgb'
structure to handle incoming and outgoing USB tranfers.  We also use
linuxlist-based msgb-queues for each endpoint.

firmware/libcommon/source/pseudo_talloc.c

@@ -0,0 +1,69 @@
+#include <stdint.h>
+
+#include "talloc.h"
+#include "trace.h"
+#include "osmocom/core/utils.h"
+
+#define NUM_RCTX_SMALL 10
+#define RCTX_SIZE_SMALL 348
+
+static uint8_t msgb_data[NUM_RCTX_SMALL][RCTX_SIZE_SMALL] __attribute__((aligned(sizeof(long))));
+static uint8_t msgb_inuse[NUM_RCTX_SMALL];
+
+void *_talloc_zero(const void *ctx, size_t size, const char *name)
+{
+	unsigned int i;
+
+	if (size > RCTX_SIZE_SMALL) {
+		TRACE_ERROR("%s() request too large(%d > %d)\r\n", __func__, size, RCTX_SIZE_SMALL);
+		return NULL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(msgb_inuse); i++) {
+		if (!msgb_inuse[i]) {
+			uint8_t *out = msgb_data[i];
+			msgb_inuse[i] = 1;
+			memset(out, 0, size);
+			return out;
+		}
+	}
+	TRACE_ERROR("%s() out of memory!\r\n", __func__);
+	return NULL;
+}
+
+int _talloc_free(void *ptr, const char *location)
+{
+	unsigned int i;
+	for (i = 0; i < ARRAY_SIZE(msgb_inuse); i++) {
+		if (ptr == msgb_data[i]) {
+			if (!msgb_inuse[i]) {
+				TRACE_ERROR("%s: double_free by \r\n", __func__, location);
+			} else {
+				msgb_inuse[i] = 0;
+			}
+			return 0;
+		}
+	}
+
+	TRACE_ERROR("%s: invalid pointer %p from %s\r\n", __func__, ptr, location);
+	return -1;
+}
+
+void talloc_set_name_const(const void *ptr, const char *name)
+{
+	/* do nothing */
+}
+
+#if 0
+void *talloc_named_const(const void *context, size_t size, const char *name)
+{
+	if (size)
+		TRACE_ERROR("%s: called with size!=0 from %s\r\n", __func__, name);
+	return NULL;
+}
+
+void *talloc_pool(const void *context, size_t size)
+{
+}
+#endif
+