Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
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 11 structures under devices/: 12 13 devices/ 14 - system/ 15 - css0/ 16 - 0.0.0000/0.0.0815/ 17 - 0.0.0001/0.0.4711/ 18 - 0.0.0002/ 19 - 0.1.0000/0.1.1234/ 20 ... 21 - defunct/ 22 23 In this example, device 0815 is accessed via subchannel 0 in subchannel set 0, 24 device 4711 via subchannel 1 in subchannel set 0, and subchannel 2 is a non-I/O 25 subchannel. Device 1234 is accessed via subchannel 0 in subchannel set 1. 26 27 The subchannel named 'defunct' does not represent any real subchannel on the 28 system; it is a pseudo subchannel where disconnected ccw devices are moved to 29 if they are displaced by another ccw device becoming operational on their 30 former subchannel. The ccw devices will be moved again to a proper subchannel 31 if they become operational again on that subchannel. 32 33 You should address a ccw device via its bus id (e.g. 0.0.4711); the device can 34 be found under bus/ccw/devices/. 35 36 All ccw devices export some data via sysfs. 37 38 cutype: The control unit type / model. 39 40 devtype: The device type / model, if applicable. 41 42 availability: Can be 'good' or 'boxed'; 'no path' or 'no device' for 43 disconnected devices. 44 45 online: An interface to set the device online and offline. 46 In the special case of the device being disconnected (see the 47 notify function under 1.2), piping 0 to online will forcibly delete 48 the device. 49 50 The device drivers can add entries to export per-device data and interfaces. 51 52 There is also some data exported on a per-subchannel basis (see under 53 bus/css/devices/): 54 55 chpids: Via which chpids the device is connected. 56 57 pimpampom: The path installed, path available and path operational masks. 58 59 There also might be additional data, for example for block devices. 60 61 62 1.1 Bringing up a ccw device 63 ---------------------------- 64 65 This is done in several steps. 66 67 a. Each driver can provide one or more parameter interfaces where parameters can 68 be specified. These interfaces are also in the driver's responsibility. 69 b. After a. has been performed, if necessary, the device is finally brought up 70 via the 'online' interface. 71 72 73 1.2 Writing a driver for ccw devices 74 ------------------------------------ 75 76 The basic struct ccw_device and struct ccw_driver data structures can be found 77 under include/asm/ccwdev.h. 78 79 struct ccw_device { 80 spinlock_t *ccwlock; 81 struct ccw_device_private *private; 82 struct ccw_device_id id; 83 84 struct ccw_driver *drv; 85 struct device dev; 86 int online; 87 88 void (*handler) (struct ccw_device *dev, unsigned long intparm, 89 struct irb *irb); 90 }; 91 92 struct ccw_driver { 93 struct module *owner; 94 struct ccw_device_id *ids; 95 int (*probe) (struct ccw_device *); 96 int (*remove) (struct ccw_device *); 97 int (*set_online) (struct ccw_device *); 98 int (*set_offline) (struct ccw_device *); 99 int (*notify) (struct ccw_device *, int); 100 struct device_driver driver; 101 char *name; 102 }; 103 104 The 'private' field contains data needed for internal i/o operation only, and 105 is not available to the device driver. 106 107 Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models 108 and/or device types/models it is interested. This information can later be found 109 in the struct ccw_device_id fields: 110 111 struct ccw_device_id { 112 __u16 match_flags; 113 114 __u16 cu_type; 115 __u16 dev_type; 116 __u8 cu_model; 117 __u8 dev_model; 118 119 unsigned long driver_info; 120 }; 121 122 The functions in ccw_driver should be used in the following way: 123 probe: This function is called by the device layer for each device the driver 124 is interested in. The driver should only allocate private structures 125 to put in dev->driver_data and create attributes (if needed). Also, 126 the interrupt handler (see below) should be set here. 127 128 int (*probe) (struct ccw_device *cdev); 129 130 Parameters: cdev - the device to be probed. 131 132 133 remove: This function is called by the device layer upon removal of the driver, 134 the device or the module. The driver should perform cleanups here. 135 136 int (*remove) (struct ccw_device *cdev); 137 138 Parameters: cdev - the device to be removed. 139 140 141 set_online: This function is called by the common I/O layer when the device is 142 activated via the 'online' attribute. The driver should finally 143 setup and activate the device here. 144 145 int (*set_online) (struct ccw_device *); 146 147 Parameters: cdev - the device to be activated. The common layer has 148 verified that the device is not already online. 149 150 151 set_offline: This function is called by the common I/O layer when the device is 152 de-activated via the 'online' attribute. The driver should shut 153 down the device, but not de-allocate its private data. 154 155 int (*set_offline) (struct ccw_device *); 156 157 Parameters: cdev - the device to be deactivated. The common layer has 158 verified that the device is online. 159 160 161 notify: This function is called by the common I/O layer for some state changes 162 of the device. 163 Signalled to the driver are: 164 * In online state, device detached (CIO_GONE) or last path gone 165 (CIO_NO_PATH). The driver must return !0 to keep the device; for 166 return code 0, the device will be deleted as usual (also when no 167 notify function is registered). If the driver wants to keep the 168 device, it is moved into disconnected state. 169 * In disconnected state, device operational again (CIO_OPER). The 170 common I/O layer performs some sanity checks on device number and 171 Device / CU to be reasonably sure if it is still the same device. 172 If not, the old device is removed and a new one registered. By the 173 return code of the notify function the device driver signals if it 174 wants the device back: !0 for keeping, 0 to make the device being 175 removed and re-registered. 176 177 int (*notify) (struct ccw_device *, int); 178 179 Parameters: cdev - the device whose state changed. 180 event - the event that happened. This can be one of CIO_GONE, 181 CIO_NO_PATH or CIO_OPER. 182 183 The handler field of the struct ccw_device is meant to be set to the interrupt 184 handler for the device. In order to accommodate drivers which use several 185 distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device 186 instead of ccw_driver. 187 The handler is registered with the common layer during set_online() processing 188 before the driver is called, and is deregistered during set_offline() after the 189 driver has been called. Also, after registering / before deregistering, path 190 grouping resp. disbanding of the path group (if applicable) are performed. 191 192 void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb); 193 194 Parameters: dev - the device the handler is called for 195 intparm - the intparm which allows the device driver to identify 196 the i/o the interrupt is associated with, or to recognize 197 the interrupt as unsolicited. 198 irb - interruption response block which contains the accumulated 199 status. 200 201 The device driver is called from the common ccw_device layer and can retrieve 202 information about the interrupt from the irb parameter. 203 204 205 1.3 ccwgroup devices 206 -------------------- 207 208 The ccwgroup mechanism is designed to handle devices consisting of multiple ccw 209 devices, like lcs or ctc. 210 211 The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to 212 this attributes creates a ccwgroup device consisting of these ccw devices (if 213 possible). This ccwgroup device can be set online or offline just like a normal 214 ccw device. 215 216 Each ccwgroup device also provides an 'ungroup' attribute to destroy the device 217 again (only when offline). This is a generic ccwgroup mechanism (the driver does 218 not need to implement anything beyond normal removal routines). 219 220 A ccw device which is a member of a ccwgroup device carries a pointer to the 221 ccwgroup device in the driver_data of its device struct. This field must not be 222 touched by the driver - it should use the ccwgroup device's driver_data for its 223 private data. 224 225 To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in 226 mind that most drivers will need to implement both a ccwgroup and a ccw 227 driver. 228 229 230 2. Channel paths 231 ----------------- 232 233 Channel paths show up, like subchannels, under the channel subsystem root (css0) 234 and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus. 235 Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect 236 only the logical state and not the physical state, since we cannot track the 237 latter consistently due to lacking machine support (we don't need to be aware 238 of it anyway). 239 240 status - Can be 'online' or 'offline'. 241 Piping 'on' or 'off' sets the chpid logically online/offline. 242 Piping 'on' to an online chpid triggers path reprobing for all devices 243 the chpid connects to. This can be used to force the kernel to re-use 244 a channel path the user knows to be online, but the machine hasn't 245 created a machine check for. 246 247 type - The physical type of the channel path. 248 249 shared - Whether the channel path is shared. 250 251 cmg - The channel measurement group. 252 253 3. System devices 254 ----------------- 255 256 3.1 xpram 257 --------- 258 259 xpram shows up under devices/system/ as 'xpram'. 260 261 3.2 cpus 262 -------- 263 264 For each cpu, a directory is created under devices/system/cpu/. Each cpu has an 265 attribute 'online' which can be 0 or 1. 266 267 268 4. Other devices 269 ---------------- 270 271 4.1 Netiucv 272 ----------- 273 274 The netiucv driver creates an attribute 'connection' under 275 bus/iucv/drivers/netiucv. Piping to this attribute creates a new netiucv 276 connection to the specified host. 277 278 Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface 279 number is assigned sequentially to the connections defined via the 'connection' 280 attribute. 281 282 user - shows the connection partner. 283 284 buffer - maximum buffer size. 285 Pipe to it to change buffer size. 286