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1 | S/390 driver model interfaces |
2 | ----------------------------- | |
3 | ||
4 | 1. CCW devices | |
5 | -------------- | |
6 | ||
7 | All devices which can be addressed by means of ccws are called 'CCW devices' - | |
8 | even if they aren't actually driven by ccws. | |
9 | ||
10 | All ccw devices are accessed via a subchannel, this is reflected in the | |
373c491f | 11 | structures under devices/: |
1da177e4 | 12 | |
373c491f CH |
13 | devices/ |
14 | - system/ | |
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15 | - css0/ |
16 | - 0.0.0000/0.0.0815/ | |
17 | - 0.0.0001/0.0.4711/ | |
18 | - 0.0.0002/ | |
dc06010c | 19 | - 0.1.0000/0.1.1234/ |
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20 | ... |
21 | ||
dc06010c CH |
22 | In this example, device 0815 is accessed via subchannel 0 in subchannel set 0, |
23 | device 4711 via subchannel 1 in subchannel set 0, and subchannel 2 is a non-I/O | |
24 | subchannel. Device 1234 is accessed via subchannel 0 in subchannel set 1. | |
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25 | |
26 | You should address a ccw device via its bus id (e.g. 0.0.4711); the device can | |
27 | be found under bus/ccw/devices/. | |
28 | ||
29 | All ccw devices export some data via sysfs. | |
30 | ||
31 | cutype: The control unit type / model. | |
32 | ||
33 | devtype: The device type / model, if applicable. | |
34 | ||
35 | availability: Can be 'good' or 'boxed'; 'no path' or 'no device' for | |
36 | disconnected devices. | |
37 | ||
38 | online: An interface to set the device online and offline. | |
39 | In the special case of the device being disconnected (see the | |
373c491f | 40 | notify function under 1.2), piping 0 to online will forcibly delete |
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41 | the device. |
42 | ||
43 | The device drivers can add entries to export per-device data and interfaces. | |
44 | ||
45 | There is also some data exported on a per-subchannel basis (see under | |
46 | bus/css/devices/): | |
47 | ||
48 | chpids: Via which chpids the device is connected. | |
49 | ||
50 | pimpampom: The path installed, path available and path operational masks. | |
51 | ||
52 | There also might be additional data, for example for block devices. | |
53 | ||
54 | ||
55 | 1.1 Bringing up a ccw device | |
56 | ---------------------------- | |
57 | ||
58 | This is done in several steps. | |
59 | ||
60 | a. Each driver can provide one or more parameter interfaces where parameters can | |
61 | be specified. These interfaces are also in the driver's responsibility. | |
62 | b. After a. has been performed, if necessary, the device is finally brought up | |
63 | via the 'online' interface. | |
64 | ||
65 | ||
66 | 1.2 Writing a driver for ccw devices | |
67 | ------------------------------------ | |
68 | ||
69 | The basic struct ccw_device and struct ccw_driver data structures can be found | |
70 | under include/asm/ccwdev.h. | |
71 | ||
72 | struct ccw_device { | |
73 | spinlock_t *ccwlock; | |
74 | struct ccw_device_private *private; | |
75 | struct ccw_device_id id; | |
76 | ||
77 | struct ccw_driver *drv; | |
78 | struct device dev; | |
79 | int online; | |
80 | ||
81 | void (*handler) (struct ccw_device *dev, unsigned long intparm, | |
82 | struct irb *irb); | |
83 | }; | |
84 | ||
85 | struct ccw_driver { | |
86 | struct module *owner; | |
87 | struct ccw_device_id *ids; | |
88 | int (*probe) (struct ccw_device *); | |
89 | int (*remove) (struct ccw_device *); | |
90 | int (*set_online) (struct ccw_device *); | |
91 | int (*set_offline) (struct ccw_device *); | |
92 | int (*notify) (struct ccw_device *, int); | |
93 | struct device_driver driver; | |
94 | char *name; | |
95 | }; | |
96 | ||
97 | The 'private' field contains data needed for internal i/o operation only, and | |
98 | is not available to the device driver. | |
99 | ||
100 | Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models | |
101 | and/or device types/models it is interested. This information can later be found | |
dc06010c | 102 | in the struct ccw_device_id fields: |
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103 | |
104 | struct ccw_device_id { | |
105 | __u16 match_flags; | |
106 | ||
107 | __u16 cu_type; | |
108 | __u16 dev_type; | |
109 | __u8 cu_model; | |
110 | __u8 dev_model; | |
111 | ||
112 | unsigned long driver_info; | |
113 | }; | |
114 | ||
115 | The functions in ccw_driver should be used in the following way: | |
116 | probe: This function is called by the device layer for each device the driver | |
117 | is interested in. The driver should only allocate private structures | |
118 | to put in dev->driver_data and create attributes (if needed). Also, | |
119 | the interrupt handler (see below) should be set here. | |
120 | ||
121 | int (*probe) (struct ccw_device *cdev); | |
122 | ||
123 | Parameters: cdev - the device to be probed. | |
124 | ||
125 | ||
126 | remove: This function is called by the device layer upon removal of the driver, | |
127 | the device or the module. The driver should perform cleanups here. | |
128 | ||
129 | int (*remove) (struct ccw_device *cdev); | |
130 | ||
131 | Parameters: cdev - the device to be removed. | |
132 | ||
133 | ||
134 | set_online: This function is called by the common I/O layer when the device is | |
135 | activated via the 'online' attribute. The driver should finally | |
136 | setup and activate the device here. | |
137 | ||
138 | int (*set_online) (struct ccw_device *); | |
139 | ||
140 | Parameters: cdev - the device to be activated. The common layer has | |
141 | verified that the device is not already online. | |
142 | ||
143 | ||
144 | set_offline: This function is called by the common I/O layer when the device is | |
145 | de-activated via the 'online' attribute. The driver should shut | |
146 | down the device, but not de-allocate its private data. | |
147 | ||
148 | int (*set_offline) (struct ccw_device *); | |
149 | ||
150 | Parameters: cdev - the device to be deactivated. The common layer has | |
151 | verified that the device is online. | |
152 | ||
153 | ||
154 | notify: This function is called by the common I/O layer for some state changes | |
155 | of the device. | |
156 | Signalled to the driver are: | |
157 | * In online state, device detached (CIO_GONE) or last path gone | |
158 | (CIO_NO_PATH). The driver must return !0 to keep the device; for | |
159 | return code 0, the device will be deleted as usual (also when no | |
160 | notify function is registerd). If the driver wants to keep the | |
161 | device, it is moved into disconnected state. | |
162 | * In disconnected state, device operational again (CIO_OPER). The | |
163 | common I/O layer performs some sanity checks on device number and | |
164 | Device / CU to be reasonably sure if it is still the same device. | |
165 | If not, the old device is removed and a new one registered. By the | |
166 | return code of the notify function the device driver signals if it | |
167 | wants the device back: !0 for keeping, 0 to make the device being | |
168 | removed and re-registered. | |
169 | ||
170 | int (*notify) (struct ccw_device *, int); | |
171 | ||
172 | Parameters: cdev - the device whose state changed. | |
173 | event - the event that happened. This can be one of CIO_GONE, | |
174 | CIO_NO_PATH or CIO_OPER. | |
175 | ||
176 | The handler field of the struct ccw_device is meant to be set to the interrupt | |
177 | handler for the device. In order to accommodate drivers which use several | |
178 | distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device | |
179 | instead of ccw_driver. | |
180 | The handler is registered with the common layer during set_online() processing | |
181 | before the driver is called, and is deregistered during set_offline() after the | |
182 | driver has been called. Also, after registering / before deregistering, path | |
183 | grouping resp. disbanding of the path group (if applicable) are performed. | |
184 | ||
185 | void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb); | |
186 | ||
187 | Parameters: dev - the device the handler is called for | |
188 | intparm - the intparm which allows the device driver to identify | |
189 | the i/o the interrupt is associated with, or to recognize | |
190 | the interrupt as unsolicited. | |
191 | irb - interruption response block which contains the accumulated | |
192 | status. | |
193 | ||
194 | The device driver is called from the common ccw_device layer and can retrieve | |
195 | information about the interrupt from the irb parameter. | |
196 | ||
197 | ||
198 | 1.3 ccwgroup devices | |
199 | -------------------- | |
200 | ||
201 | The ccwgroup mechanism is designed to handle devices consisting of multiple ccw | |
202 | devices, like lcs or ctc. | |
203 | ||
204 | The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to | |
205 | this attributes creates a ccwgroup device consisting of these ccw devices (if | |
206 | possible). This ccwgroup device can be set online or offline just like a normal | |
207 | ccw device. | |
208 | ||
209 | Each ccwgroup device also provides an 'ungroup' attribute to destroy the device | |
210 | again (only when offline). This is a generic ccwgroup mechanism (the driver does | |
211 | not need to implement anything beyond normal removal routines). | |
212 | ||
dc06010c CH |
213 | A ccw device which is a member of a ccwgroup device carries a pointer to the |
214 | ccwgroup device in the driver_data of its device struct. This field must not be | |
215 | touched by the driver - it should use the ccwgroup device's driver_data for its | |
216 | private data. | |
217 | ||
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218 | To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in |
219 | mind that most drivers will need to implement both a ccwgroup and a ccw driver | |
220 | (unless you have a meta ccw driver, like cu3088 for lcs and ctc). | |
221 | ||
222 | ||
223 | 2. Channel paths | |
224 | ----------------- | |
225 | ||
226 | Channel paths show up, like subchannels, under the channel subsystem root (css0) | |
227 | and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus. | |
228 | Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect | |
229 | only the logical state and not the physical state, since we cannot track the | |
230 | latter consistently due to lacking machine support (we don't need to be aware | |
373c491f | 231 | of it anyway). |
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232 | |
233 | status - Can be 'online' or 'offline'. | |
234 | Piping 'on' or 'off' sets the chpid logically online/offline. | |
235 | Piping 'on' to an online chpid triggers path reprobing for all devices | |
236 | the chpid connects to. This can be used to force the kernel to re-use | |
237 | a channel path the user knows to be online, but the machine hasn't | |
238 | created a machine check for. | |
239 | ||
dc06010c CH |
240 | type - The physical type of the channel path. |
241 | ||
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242 | |
243 | 3. System devices | |
244 | ----------------- | |
245 | ||
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246 | 3.1 xpram |
247 | --------- | |
248 | ||
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249 | xpram shows up under devices/system/ as 'xpram'. |
250 | ||
251 | 3.2 cpus | |
252 | -------- | |
253 | ||
254 | For each cpu, a directory is created under devices/system/cpu/. Each cpu has an | |
255 | attribute 'online' which can be 0 or 1. | |
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256 | |
257 | ||
258 | 4. Other devices | |
259 | ---------------- | |
260 | ||
261 | 4.1 Netiucv | |
262 | ----------- | |
263 | ||
264 | The netiucv driver creates an attribute 'connection' under | |
265 | bus/iucv/drivers/netiucv. Piping to this attibute creates a new netiucv | |
266 | connection to the specified host. | |
267 | ||
268 | Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface | |
269 | number is assigned sequentially to the connections defined via the 'connection' | |
270 | attribute. | |
271 | ||
272 | user - shows the connection partner. | |
273 | ||
274 | buffer - maximum buffer size. | |
275 | Pipe to it to change buffer size. | |
276 | ||
277 |