1 files changed, 85 insertions, 0 deletions
diff --git a/sound/firewire/lib.c b/sound/firewire/lib.c
new file mode 100644
index 000000000000..4750cea2210e
--- /dev/null
+++ b/sound/firewire/lib.c
@@ -0,0 +1,85 @@
+/*
+ * miscellaneous helper functions
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ * Licensed under the terms of the GNU General Public License, version 2.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/module.h>
+#include "lib.h"
+
+#define ERROR_RETRY_DELAY_MS	5
+
+/**
+ * rcode_string - convert a firewire result code to a string
+ * @rcode: the result
+ */
+const char *rcode_string(unsigned int rcode)
+{
+	static const char *const names[] = {
+		[RCODE_COMPLETE]	= "complete",
+		[RCODE_CONFLICT_ERROR]	= "conflict error",
+		[RCODE_DATA_ERROR]	= "data error",
+		[RCODE_TYPE_ERROR]	= "type error",
+		[RCODE_ADDRESS_ERROR]	= "address error",
+		[RCODE_SEND_ERROR]	= "send error",
+		[RCODE_CANCELLED]	= "cancelled",
+		[RCODE_BUSY]		= "busy",
+		[RCODE_GENERATION]	= "generation",
+		[RCODE_NO_ACK]		= "no ack",
+	};
+
+	if (rcode < ARRAY_SIZE(names) && names[rcode])
+		return names[rcode];
+	else
+		return "unknown";
+}
+EXPORT_SYMBOL(rcode_string);
+
+/**
+ * snd_fw_transaction - send a request and wait for its completion
+ * @unit: the driver's unit on the target device
+ * @tcode: the transaction code
+ * @offset: the address in the target's address space
+ * @buffer: input/output data
+ * @length: length of @buffer
+ *
+ * Submits an asynchronous request to the target device, and waits for the
+ * response.  The node ID and the current generation are derived from @unit.
+ * On a bus reset or an error, the transaction is retried a few times.
+ * Returns zero on success, or a negative error code.
+ */
+int snd_fw_transaction(struct fw_unit *unit, int tcode,
+		       u64 offset, void *buffer, size_t length)
+{
+	struct fw_device *device = fw_parent_device(unit);
+	int generation, rcode, tries = 0;
+
+	for (;;) {
+		generation = device->generation;
+		smp_rmb(); /* node_id vs. generation */
+		rcode = fw_run_transaction(device->card, tcode,
+					   device->node_id, generation,
+					   device->max_speed, offset,
+					   buffer, length);
+
+		if (rcode == RCODE_COMPLETE)
+			return 0;
+
+		if (rcode_is_permanent_error(rcode) || ++tries >= 3) {
+			dev_err(&unit->device, "transaction failed: %s\n",
+				rcode_string(rcode));
+			return -EIO;
+		}
+
+		msleep(ERROR_RETRY_DELAY_MS);
+	}
+}
+EXPORT_SYMBOL(snd_fw_transaction);
+
+MODULE_DESCRIPTION("FireWire audio helper functions");
+MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
+MODULE_LICENSE("GPL v2");