/Documentation/s390/driver-model.txt
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1S/390 driver model interfaces 2----------------------------- 3 41. CCW devices 5-------------- 6 7All devices which can be addressed by means of ccws are called 'CCW devices' - 8even if they aren't actually driven by ccws. 9 10All ccw devices are accessed via a subchannel, this is reflected in the 11structures under root/: 12 13root/ 14 - sys 15 - legacy 16 - css0/ 17 - 0.0.0000/0.0.0815/ 18 - 0.0.0001/0.0.4711/ 19 - 0.0.0002/ 20 ... 21 22In this example, device 0815 is accessed via subchannel 0, device 4711 via 23subchannel 1, and subchannel 2 is a non-I/O subchannel. 24 25You should address a ccw device via its bus id (e.g. 0.0.4711); the device can 26be found under bus/ccw/devices/. 27 28All ccw devices export some data via sysfs. 29 30cutype: The control unit type / model. 31 32devtype: The device type / model, if applicable. 33 34availability: Can be 'good' or 'boxed'; 'no path' or 'no device' for 35 disconnected devices. 36 37online: An interface to set the device online and offline. 38 In the special case of the device being disconnected (see the 39 notify function under 1.2), piping 0 to online will focibly delete 40 the device. 41 42The device drivers can add entries to export per-device data and interfaces. 43 44There is also some data exported on a per-subchannel basis (see under 45bus/css/devices/): 46 47chpids: Via which chpids the device is connected. 48 49pimpampom: The path installed, path available and path operational masks. 50 51There also might be additional data, for example for block devices. 52 53 541.1 Bringing up a ccw device 55---------------------------- 56 57This is done in several steps. 58 59a. Each driver can provide one or more parameter interfaces where parameters can 60 be specified. These interfaces are also in the driver's responsibility. 61b. After a. has been performed, if necessary, the device is finally brought up 62 via the 'online' interface. 63 64 651.2 Writing a driver for ccw devices 66------------------------------------ 67 68The basic struct ccw_device and struct ccw_driver data structures can be found 69under include/asm/ccwdev.h. 70 71struct ccw_device { 72 spinlock_t *ccwlock; 73 struct ccw_device_private *private; 74 struct ccw_device_id id; 75 76 struct ccw_driver *drv; 77 struct device dev; 78 int online; 79 80 void (*handler) (struct ccw_device *dev, unsigned long intparm, 81 struct irb *irb); 82}; 83 84struct ccw_driver { 85 struct module *owner; 86 struct ccw_device_id *ids; 87 int (*probe) (struct ccw_device *); 88 int (*remove) (struct ccw_device *); 89 int (*set_online) (struct ccw_device *); 90 int (*set_offline) (struct ccw_device *); 91 int (*notify) (struct ccw_device *, int); 92 struct device_driver driver; 93 char *name; 94}; 95 96The 'private' field contains data needed for internal i/o operation only, and 97is not available to the device driver. 98 99Each driver should declare in a MODULE_DEVICE_TABLE into which CU types/models 100and/or device types/models it is interested. This information can later be found 101found in the struct ccw_device_id fields: 102 103struct ccw_device_id { 104 __u16 match_flags; 105 106 __u16 cu_type; 107 __u16 dev_type; 108 __u8 cu_model; 109 __u8 dev_model; 110 111 unsigned long driver_info; 112}; 113 114The functions in ccw_driver should be used in the following way: 115probe: This function is called by the device layer for each device the driver 116 is interested in. The driver should only allocate private structures 117 to put in dev->driver_data and create attributes (if needed). Also, 118 the interrupt handler (see below) should be set here. 119 120int (*probe) (struct ccw_device *cdev); 121 122Parameters: cdev - the device to be probed. 123 124 125remove: This function is called by the device layer upon removal of the driver, 126 the device or the module. The driver should perform cleanups here. 127 128int (*remove) (struct ccw_device *cdev); 129 130Parameters: cdev - the device to be removed. 131 132 133set_online: This function is called by the common I/O layer when the device is 134 activated via the 'online' attribute. The driver should finally 135 setup and activate the device here. 136 137int (*set_online) (struct ccw_device *); 138 139Parameters: cdev - the device to be activated. The common layer has 140 verified that the device is not already online. 141 142 143set_offline: This function is called by the common I/O layer when the device is 144 de-activated via the 'online' attribute. The driver should shut 145 down the device, but not de-allocate its private data. 146 147int (*set_offline) (struct ccw_device *); 148 149Parameters: cdev - the device to be deactivated. The common layer has 150 verified that the device is online. 151 152 153notify: This function is called by the common I/O layer for some state changes 154 of the device. 155 Signalled to the driver are: 156 * In online state, device detached (CIO_GONE) or last path gone 157 (CIO_NO_PATH). The driver must return !0 to keep the device; for 158 return code 0, the device will be deleted as usual (also when no 159 notify function is registerd). If the driver wants to keep the 160 device, it is moved into disconnected state. 161 * In disconnected state, device operational again (CIO_OPER). The 162 common I/O layer performs some sanity checks on device number and 163 Device / CU to be reasonably sure if it is still the same device. 164 If not, the old device is removed and a new one registered. By the 165 return code of the notify function the device driver signals if it 166 wants the device back: !0 for keeping, 0 to make the device being 167 removed and re-registered. 168 169int (*notify) (struct ccw_device *, int); 170 171Parameters: cdev - the device whose state changed. 172 event - the event that happened. This can be one of CIO_GONE, 173 CIO_NO_PATH or CIO_OPER. 174 175The handler field of the struct ccw_device is meant to be set to the interrupt 176handler for the device. In order to accommodate drivers which use several 177distinct handlers (e.g. multi subchannel devices), this is a member of ccw_device 178instead of ccw_driver. 179The handler is registered with the common layer during set_online() processing 180before the driver is called, and is deregistered during set_offline() after the 181driver has been called. Also, after registering / before deregistering, path 182grouping resp. disbanding of the path group (if applicable) are performed. 183 184void (*handler) (struct ccw_device *dev, unsigned long intparm, struct irb *irb); 185 186Parameters: dev - the device the handler is called for 187 intparm - the intparm which allows the device driver to identify 188 the i/o the interrupt is associated with, or to recognize 189 the interrupt as unsolicited. 190 irb - interruption response block which contains the accumulated 191 status. 192 193The device driver is called from the common ccw_device layer and can retrieve 194information about the interrupt from the irb parameter. 195 196 1971.3 ccwgroup devices 198-------------------- 199 200The ccwgroup mechanism is designed to handle devices consisting of multiple ccw 201devices, like lcs or ctc. 202 203The ccw driver provides a 'group' attribute. Piping bus ids of ccw devices to 204this attributes creates a ccwgroup device consisting of these ccw devices (if 205possible). This ccwgroup device can be set online or offline just like a normal 206ccw device. 207 208Each ccwgroup device also provides an 'ungroup' attribute to destroy the device 209again (only when offline). This is a generic ccwgroup mechanism (the driver does 210not need to implement anything beyond normal removal routines). 211 212To implement a ccwgroup driver, please refer to include/asm/ccwgroup.h. Keep in 213mind that most drivers will need to implement both a ccwgroup and a ccw driver 214(unless you have a meta ccw driver, like cu3088 for lcs and ctc). 215 216 2172. Channel paths 218----------------- 219 220Channel paths show up, like subchannels, under the channel subsystem root (css0) 221and are called 'chp0.<chpid>'. They have no driver and do not belong to any bus. 222Please note, that unlike /proc/chpids in 2.4, the channel path objects reflect 223only the logical state and not the physical state, since we cannot track the 224latter consistently due to lacking machine support (we don't need to be aware 225of anyway). 226 227status - Can be 'online' or 'offline'. 228 Piping 'on' or 'off' sets the chpid logically online/offline. 229 Piping 'on' to an online chpid triggers path reprobing for all devices 230 the chpid connects to. This can be used to force the kernel to re-use 231 a channel path the user knows to be online, but the machine hasn't 232 created a machine check for. 233 234 2353. System devices 236----------------- 237 238Note: cpus may yet be added here. 239 2403.1 xpram 241--------- 242 243xpram shows up under sys/ as 'xpram'. 244 245 2464. Other devices 247---------------- 248 2494.1 Netiucv 250----------- 251 252The netiucv driver creates an attribute 'connection' under 253bus/iucv/drivers/netiucv. Piping to this attibute creates a new netiucv 254connection to the specified host. 255 256Netiucv connections show up under devices/iucv/ as "netiucv<ifnum>". The interface 257number is assigned sequentially to the connections defined via the 'connection' 258attribute. 259 260user - shows the connection partner. 261 262buffer - maximum buffer size. 263 Pipe to it to change buffer size. 264 265