xref: /kernel/linux/linux-5.10/sound/firewire/lib.c (revision 8c2ecf20) 
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 */
33int 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}
68EXPORT_SYMBOL(snd_fw_transaction);
69
70#define PROBE_DELAY_MS		(2 * MSEC_PER_SEC)
71
72/**
73 * snd_fw_schedule_registration - schedule work for sound card registration
74 * @unit: an instance for unit on IEEE 1394 bus
75 * @dwork: delayed work with callback function
76 *
77 * This function is not designed for general purposes. When new unit is
78 * connected to IEEE 1394 bus, the bus is under bus-reset state because of
79 * topological change. In this state, units tend to fail both of asynchronous
80 * and isochronous communication. To avoid this problem, this function is used
81 * to postpone sound card registration after the state. The callers must
82 * set up instance of delayed work in advance.
83 */
84void snd_fw_schedule_registration(struct fw_unit *unit,
85				  struct delayed_work *dwork)
86{
87	u64 now, delay;
88
89	now = get_jiffies_64();
90	delay = fw_parent_device(unit)->card->reset_jiffies
91					+ msecs_to_jiffies(PROBE_DELAY_MS);
92
93	if (time_after64(delay, now))
94		delay -= now;
95	else
96		delay = 0;
97
98	mod_delayed_work(system_wq, dwork, delay);
99}
100EXPORT_SYMBOL(snd_fw_schedule_registration);
101
102MODULE_DESCRIPTION("FireWire audio helper functions");
103MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
104MODULE_LICENSE("GPL v2");
105