1 files changed, 104 insertions, 0 deletions
diff --git a/sound/firewire/lib.c b/sound/firewire/lib.c
new file mode 100644
index 000000000..85c4f4477
--- /dev/null
+++ b/sound/firewire/lib.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * miscellaneous helper functions
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/firewire.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "lib.h"
+
+#define ERROR_RETRY_DELAY_MS	20
+
+/**
+ * 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
+ * @flags: use %FW_FIXED_GENERATION and add the generation value to attempt the
+ *         request only in that generation; use %FW_QUIET to suppress error
+ *         messages
+ *
+ * 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,
+		       unsigned int flags)
+{
+	struct fw_device *device = fw_parent_device(unit);
+	int generation, rcode, tries = 0;
+
+	generation = flags & FW_GENERATION_MASK;
+	for (;;) {
+		if (!(flags & FW_FIXED_GENERATION)) {
+			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 == RCODE_GENERATION && (flags & FW_FIXED_GENERATION))
+			return -EAGAIN;
+
+		if (rcode_is_permanent_error(rcode) || ++tries >= 3) {
+			if (!(flags & FW_QUIET))
+				dev_err(&unit->device,
+					"transaction failed: %s\n",
+					fw_rcode_string(rcode));
+			return -EIO;
+		}
+
+		msleep(ERROR_RETRY_DELAY_MS);
+	}
+}
+EXPORT_SYMBOL(snd_fw_transaction);
+
+#define PROBE_DELAY_MS		(2 * MSEC_PER_SEC)
+
+/**
+ * snd_fw_schedule_registration - schedule work for sound card registration
+ * @unit: an instance for unit on IEEE 1394 bus
+ * @dwork: delayed work with callback function
+ *
+ * This function is not designed for general purposes. When new unit is
+ * connected to IEEE 1394 bus, the bus is under bus-reset state because of
+ * topological change. In this state, units tend to fail both of asynchronous
+ * and isochronous communication. To avoid this problem, this function is used
+ * to postpone sound card registration after the state. The callers must
+ * set up instance of delayed work in advance.
+ */
+void snd_fw_schedule_registration(struct fw_unit *unit,
+				  struct delayed_work *dwork)
+{
+	u64 now, delay;
+
+	now = get_jiffies_64();
+	delay = fw_parent_device(unit)->card->reset_jiffies
+					+ msecs_to_jiffies(PROBE_DELAY_MS);
+
+	if (time_after64(delay, now))
+		delay -= now;
+	else
+		delay = 0;
+
+	mod_delayed_work(system_wq, dwork, delay);
+}
+EXPORT_SYMBOL(snd_fw_schedule_registration);
+
+MODULE_DESCRIPTION("FireWire audio helper functions");
+MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
+MODULE_LICENSE("GPL v2");