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  */
snd_fw_transaction(struct fw_unit * unit,int tcode,u64 offset,void * buffer,size_t length,unsigned int flags)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 v2");
73