1 /*
2 * Function Control Protocol (IEC 61883-1) helper functions
3 *
4 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
5 * Licensed under the terms of the GNU General Public License, version 2.
6 */
7
8 #include <linux/device.h>
9 #include <linux/firewire.h>
10 #include <linux/firewire-constants.h>
11 #include <linux/list.h>
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/spinlock.h>
15 #include <linux/wait.h>
16 #include <linux/delay.h>
17 #include "fcp.h"
18 #include "lib.h"
19
20 #define CTS_AVC 0x00
21
22 #define ERROR_RETRIES 3
23 #define ERROR_DELAY_MS 5
24 #define FCP_TIMEOUT_MS 125
25
26 static DEFINE_SPINLOCK(transactions_lock);
27 static LIST_HEAD(transactions);
28
29 enum fcp_state {
30 STATE_PENDING,
31 STATE_BUS_RESET,
32 STATE_COMPLETE,
33 };
34
35 struct fcp_transaction {
36 struct list_head list;
37 struct fw_unit *unit;
38 void *response_buffer;
39 unsigned int response_size;
40 unsigned int response_match_bytes;
41 enum fcp_state state;
42 wait_queue_head_t wait;
43 };
44
45 /**
46 * fcp_avc_transaction - send an AV/C command and wait for its response
47 * @unit: a unit on the target device
48 * @command: a buffer containing the command frame; must be DMA-able
49 * @command_size: the size of @command
50 * @response: a buffer for the response frame
51 * @response_size: the maximum size of @response
52 * @response_match_bytes: a bitmap specifying the bytes used to detect the
53 * correct response frame
54 *
55 * This function sends a FCP command frame to the target and waits for the
56 * corresponding response frame to be returned.
57 *
58 * Because it is possible for multiple FCP transactions to be active at the
59 * same time, the correct response frame is detected by the value of certain
60 * bytes. These bytes must be set in @response before calling this function,
61 * and the corresponding bits must be set in @response_match_bytes.
62 *
63 * @command and @response can point to the same buffer.
64 *
65 * Asynchronous operation (INTERIM, NOTIFY) is not supported at the moment.
66 *
67 * Returns the actual size of the response frame, or a negative error code.
68 */
fcp_avc_transaction(struct fw_unit * unit,const void * command,unsigned int command_size,void * response,unsigned int response_size,unsigned int response_match_bytes)69 int fcp_avc_transaction(struct fw_unit *unit,
70 const void *command, unsigned int command_size,
71 void *response, unsigned int response_size,
72 unsigned int response_match_bytes)
73 {
74 struct fcp_transaction t;
75 int tcode, ret, tries = 0;
76
77 t.unit = unit;
78 t.response_buffer = response;
79 t.response_size = response_size;
80 t.response_match_bytes = response_match_bytes;
81 t.state = STATE_PENDING;
82 init_waitqueue_head(&t.wait);
83
84 spin_lock_irq(&transactions_lock);
85 list_add_tail(&t.list, &transactions);
86 spin_unlock_irq(&transactions_lock);
87
88 for (;;) {
89 tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
90 : TCODE_WRITE_BLOCK_REQUEST;
91 ret = snd_fw_transaction(t.unit, tcode,
92 CSR_REGISTER_BASE + CSR_FCP_COMMAND,
93 (void *)command, command_size);
94 if (ret < 0)
95 break;
96
97 wait_event_timeout(t.wait, t.state != STATE_PENDING,
98 msecs_to_jiffies(FCP_TIMEOUT_MS));
99
100 if (t.state == STATE_COMPLETE) {
101 ret = t.response_size;
102 break;
103 } else if (t.state == STATE_BUS_RESET) {
104 msleep(ERROR_DELAY_MS);
105 } else if (++tries >= ERROR_RETRIES) {
106 dev_err(&t.unit->device, "FCP command timed out\n");
107 ret = -EIO;
108 break;
109 }
110 }
111
112 spin_lock_irq(&transactions_lock);
113 list_del(&t.list);
114 spin_unlock_irq(&transactions_lock);
115
116 return ret;
117 }
118 EXPORT_SYMBOL(fcp_avc_transaction);
119
120 /**
121 * fcp_bus_reset - inform the target handler about a bus reset
122 * @unit: the unit that might be used by fcp_avc_transaction()
123 *
124 * This function must be called from the driver's .update handler to inform
125 * the FCP transaction handler that a bus reset has happened. Any pending FCP
126 * transactions are retried.
127 */
fcp_bus_reset(struct fw_unit * unit)128 void fcp_bus_reset(struct fw_unit *unit)
129 {
130 struct fcp_transaction *t;
131
132 spin_lock_irq(&transactions_lock);
133 list_for_each_entry(t, &transactions, list) {
134 if (t->unit == unit &&
135 t->state == STATE_PENDING) {
136 t->state = STATE_BUS_RESET;
137 wake_up(&t->wait);
138 }
139 }
140 spin_unlock_irq(&transactions_lock);
141 }
142 EXPORT_SYMBOL(fcp_bus_reset);
143
144 /* checks whether the response matches the masked bytes in response_buffer */
is_matching_response(struct fcp_transaction * transaction,const void * response,size_t length)145 static bool is_matching_response(struct fcp_transaction *transaction,
146 const void *response, size_t length)
147 {
148 const u8 *p1, *p2;
149 unsigned int mask, i;
150
151 p1 = response;
152 p2 = transaction->response_buffer;
153 mask = transaction->response_match_bytes;
154
155 for (i = 0; ; ++i) {
156 if ((mask & 1) && p1[i] != p2[i])
157 return false;
158 mask >>= 1;
159 if (!mask)
160 return true;
161 if (--length == 0)
162 return false;
163 }
164 }
165
fcp_response(struct fw_card * card,struct fw_request * request,int tcode,int destination,int source,int generation,unsigned long long offset,void * data,size_t length,void * callback_data)166 static void fcp_response(struct fw_card *card, struct fw_request *request,
167 int tcode, int destination, int source,
168 int generation, unsigned long long offset,
169 void *data, size_t length, void *callback_data)
170 {
171 struct fcp_transaction *t;
172 unsigned long flags;
173
174 if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
175 return;
176
177 spin_lock_irqsave(&transactions_lock, flags);
178 list_for_each_entry(t, &transactions, list) {
179 struct fw_device *device = fw_parent_device(t->unit);
180 if (device->card != card ||
181 device->generation != generation)
182 continue;
183 smp_rmb(); /* node_id vs. generation */
184 if (device->node_id != source)
185 continue;
186
187 if (t->state == STATE_PENDING &&
188 is_matching_response(t, data, length)) {
189 t->state = STATE_COMPLETE;
190 t->response_size = min((unsigned int)length,
191 t->response_size);
192 memcpy(t->response_buffer, data, t->response_size);
193 wake_up(&t->wait);
194 }
195 }
196 spin_unlock_irqrestore(&transactions_lock, flags);
197 }
198
199 static struct fw_address_handler response_register_handler = {
200 .length = 0x200,
201 .address_callback = fcp_response,
202 };
203
fcp_module_init(void)204 static int __init fcp_module_init(void)
205 {
206 static const struct fw_address_region response_register_region = {
207 .start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
208 .end = CSR_REGISTER_BASE + CSR_FCP_END,
209 };
210
211 fw_core_add_address_handler(&response_register_handler,
212 &response_register_region);
213
214 return 0;
215 }
216
fcp_module_exit(void)217 static void __exit fcp_module_exit(void)
218 {
219 WARN_ON(!list_empty(&transactions));
220 fw_core_remove_address_handler(&response_register_handler);
221 }
222
223 module_init(fcp_module_init);
224 module_exit(fcp_module_exit);
225