1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * miscellaneous helper functions
4 *
5 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
6 */
7
8 #include <linux/delay.h>
9 #include <linux/device.h>
10 #include <linux/firewire.h>
11 #include <linux/module.h>
12 #include <linux/slab.h>
13 #include "lib.h"
14
15 #define ERROR_RETRY_DELAY_MS 20
16
17 /**
18 * snd_fw_transaction - send a request and wait for its completion
19 * @unit: the driver's unit on the target device
20 * @tcode: the transaction code
21 * @offset: the address in the target's address space
22 * @buffer: input/output data
23 * @length: length of @buffer
24 * @flags: use %FW_FIXED_GENERATION and add the generation value to attempt the
25 * request only in that generation; use %FW_QUIET to suppress error
26 * messages
27 *
28 * Submits an asynchronous request to the target device, and waits for the
29 * response. The node ID and the current generation are derived from @unit.
30 * On a bus reset or an error, the transaction is retried a few times.
31 * Returns zero on success, or a negative error code.
32 */
33 int snd_fw_transaction(struct fw_unit *unit, int tcode,
34 u64 offset, void *buffer, size_t length,
35 unsigned int flags)
36 {
37 struct fw_device *device = fw_parent_device(unit);
38 int generation, rcode, tries = 0;
39
40 generation = flags & FW_GENERATION_MASK;
41 for (;;) {
42 if (!(flags & FW_FIXED_GENERATION)) {
43 generation = device->generation;
44 smp_rmb(); /* node_id vs. generation */
45 }
46 rcode = fw_run_transaction(device->card, tcode,
47 device->node_id, generation,
48 device->max_speed, offset,
49 buffer, length);
50
51 if (rcode == RCODE_COMPLETE)
52 return 0;
53
54 if (rcode == RCODE_GENERATION && (flags & FW_FIXED_GENERATION))
55 return -EAGAIN;
56
57 if (rcode_is_permanent_error(rcode) || ++tries >= 3) {
58 if (!(flags & FW_QUIET))
59 dev_err(&unit->device,
60 "transaction failed: %s\n",
61 fw_rcode_string(rcode));
62 return -EIO;
63 }
64
65 msleep(ERROR_RETRY_DELAY_MS);
66 }
67 }
68 EXPORT_SYMBOL(snd_fw_transaction);
69
70 MODULE_DESCRIPTION("FireWire audio helper functions");
71 MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
72 MODULE_LICENSE("GPL");
73
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