Writing s390 channel device drivers¶

Author:: Cornelia Huck

Introduction¶

This document describes the interfaces available for device drivers that drive s390 based channel attached I/O devices. This includes interfaces for interaction with the hardware and interfaces for interacting with the common driver core. Those interfaces are provided by the s390 common I/O layer.

The document assumes a familarity with the technical terms associated with the s390 channel I/O architecture. For a description of this architecture, please refer to the “z/Architecture: Principles of Operation”, IBM publication no. SA22-7832.

While most I/O devices on a s390 system are typically driven through the channel I/O mechanism described here, there are various other methods (like the diag interface). These are out of the scope of this document.

The s390 common I/O layer also provides access to some devices that are not strictly considered I/O devices. They are considered here as well, although they are not the focus of this document.

Some additional information can also be found in the kernel source under Documentation/s390/driver-model.rst.

The css bus¶

The css bus contains the subchannels available on the system. They fall into several categories:

Standard I/O subchannels, for use by the system. They have a child device on the ccw bus and are described below.
I/O subchannels bound to the vfio-ccw driver. See Documentation/s390/vfio-ccw.rst.
Message subchannels. No Linux driver currently exists.
CHSC subchannels (at most one). The chsc subchannel driver can be used to send asynchronous chsc commands.
eADM subchannels. Used for talking to storage class memory.

The ccw bus¶

The ccw bus typically contains the majority of devices available to a s390 system. Named after the channel command word (ccw), the basic command structure used to address its devices, the ccw bus contains so-called channel attached devices. They are addressed via I/O subchannels, visible on the css bus. A device driver for channel-attached devices, however, will never interact with the subchannel directly, but only via the I/O device on the ccw bus, the ccw device.

I/O functions for channel-attached devices¶

Some hardware structures have been translated into C structures for use by the common I/O layer and device drivers. For more information on the hardware structures represented here, please consult the Principles of Operation.

struct ccw1: channel command word

Definition

struct ccw1 {
  __u8 cmd_code;
  __u8 flags;
  __u16 count;
  __u32 cda;
};

Members

cmd_code: command code
flags: flags, like IDA addressing, etc.
count: byte count
cda: data address

Description

The ccw is the basic structure to build channel programs that perform operations with the device or the control unit. Only Format-1 channel command words are supported.

struct ccw0: channel command word

Definition

struct ccw0 {
  __u8 cmd_code;
  __u32 cda : 24;
  __u8 flags;
  __u8 reserved;
  __u16 count;
};

Members

cmd_code: command code
cda: data address
flags: flags, like IDA addressing, etc.
reserved: will be ignored
count: byte count

Description

The format-0 ccw structure.

struct erw: extended report word

Definition

struct erw {
  __u32 res0  : 3;
  __u32 auth  : 1;
  __u32 pvrf  : 1;
  __u32 cpt   : 1;
  __u32 fsavf : 1;
  __u32 cons  : 1;
  __u32 scavf : 1;
  __u32 fsaf  : 1;
  __u32 scnt  : 6;
  __u32 res16 : 16;
};

Members

res0: reserved
auth: authorization check
pvrf: path-verification-required flag
cpt: channel-path timeout
fsavf: failing storage address validity flag
cons: concurrent sense
scavf: secondary ccw address validity flag
fsaf: failing storage address format
scnt: sense count, if cons == 1
res16: reserved

struct erw_eadm: EADM Subchannel extended report word

Definition

struct erw_eadm {
  __u32 : 16;
  __u32 b : 1;
  __u32 r : 1;
  __u32 : 14;
};

Members

b: aob error
r: arsb error

struct sublog: subchannel logout area

Definition

struct sublog {
  __u32 res0  : 1;
  __u32 esf   : 7;
  __u32 lpum  : 8;
  __u32 arep  : 1;
  __u32 fvf   : 5;
  __u32 sacc  : 2;
  __u32 termc : 2;
  __u32 devsc : 1;
  __u32 serr  : 1;
  __u32 ioerr : 1;
  __u32 seqc  : 3;
};

Members

res0: reserved
esf: extended status flags
lpum: last path used mask
arep: ancillary report
fvf: field-validity flags
sacc: storage access code
termc: termination code
devsc: device-status check
serr: secondary error
ioerr: i/o-error alert
seqc: sequence code

struct esw0: Format 0 Extended Status Word (ESW)

Definition

struct esw0 {
  struct sublog sublog;
  struct erw erw;
  __u32 faddr[2];
  __u32 saddr;
};

Members

sublog: subchannel logout
erw: extended report word
faddr: failing storage address
saddr: secondary ccw address

struct esw1: Format 1 Extended Status Word (ESW)

Definition

struct esw1 {
  __u8 zero0;
  __u8 lpum;
  __u16 zero16;
  struct erw erw;
  __u32 zeros[3];
};

Members

zero0: reserved zeros
lpum: last path used mask
zero16: reserved zeros
erw: extended report word
zeros: three fullwords of zeros

struct esw2: Format 2 Extended Status Word (ESW)

Definition

struct esw2 {
  __u8 zero0;
  __u8 lpum;
  __u16 dcti;
  struct erw erw;
  __u32 zeros[3];
};

Members

zero0: reserved zeros
lpum: last path used mask
dcti: device-connect-time interval
erw: extended report word
zeros: three fullwords of zeros

struct esw3: Format 3 Extended Status Word (ESW)

Definition

struct esw3 {
  __u8 zero0;
  __u8 lpum;
  __u16 res;
  struct erw erw;
  __u32 zeros[3];
};

Members

zero0: reserved zeros
lpum: last path used mask
res: reserved
erw: extended report word
zeros: three fullwords of zeros

struct esw_eadm: EADM Subchannel Extended Status Word (ESW)

Definition

struct esw_eadm {
  __u32 sublog;
  struct erw_eadm erw;
  __u32 : 32;
  __u32 : 32;
  __u32 : 32;
};

Members

sublog: subchannel logout
erw: extended report word

struct irb: interruption response block

Definition

struct irb {
  union scsw scsw;
  union {
    struct esw0 esw0;
    struct esw1 esw1;
    struct esw2 esw2;
    struct esw3 esw3;
    struct esw_eadm eadm;
  } esw;
  __u8 ecw[32];
};

Members

scsw: subchannel status word
esw: extended status word
ecw: extended control word

Description

The irb that is handed to the device driver when an interrupt occurs. For solicited interrupts, the common I/O layer already performs checks whether a field is valid; a field not being valid is always passed as 0. If a unit check occurred, ecw may contain sense data; this is retrieved by the common I/O layer itself if the device doesn’t support concurrent sense (so that the device driver never needs to perform basic sense itself). For unsolicited interrupts, the irb is passed as-is (expect for sense data, if applicable).

struct ciw: command information word (CIW) layout

Definition

struct ciw {
  __u32 et       :  2;
  __u32 reserved :  2;
  __u32 ct       :  4;
  __u32 cmd      :  8;
  __u32 count    : 16;
};

Members

et: entry type
reserved: reserved bits
ct: command type
cmd: command code
count: command count

struct ccw_dev_id: unique identifier for ccw devices

Definition

struct ccw_dev_id {
  u8 ssid;
  u16 devno;
};

Members

ssid: subchannel set id
devno: device number

Description

This structure is not directly based on any hardware structure. The hardware identifies a device by its device number and its subchannel, which is in turn identified by its id. In order to get a unique identifier for ccw devices across subchannel sets, struct ccw_dev_id has been introduced.

int ccw_dev_id_is_equal(struct ccw_dev_id *dev_id1, struct ccw_dev_id *dev_id2)¶: compare two ccw_dev_ids

Parameters

struct ccw_dev_id * dev_id1: a ccw_dev_id
struct ccw_dev_id * dev_id2: another ccw_dev_id

Return

1 if the two structures are equal field-by-field, 0 if not.

Context

any

u8 pathmask_to_pos(u8 mask)¶: find the position of the left-most bit in a pathmask

Parameters

u8 mask: pathmask with at least one bit set

ccw devices¶

Devices that want to initiate channel I/O need to attach to the ccw bus. Interaction with the driver core is done via the common I/O layer, which provides the abstractions of ccw devices and ccw device drivers.

The functions that initiate or terminate channel I/O all act upon a ccw device structure. Device drivers must not bypass those functions or strange side effects may happen.

struct ccw_device: channel attached device

Definition

struct ccw_device {
  spinlock_t *ccwlock;
  struct ccw_device_id id;
  struct ccw_driver *drv;
  struct device dev;
  int online;
  void (*handler) (struct ccw_device *, unsigned long, struct irb *);
};

Members

ccwlock: pointer to device lock
id: id of this device
drv: ccw driver for this device
dev: embedded device structure
online: online status of device
handler: interrupt handler

Description

handler is a member of the device rather than the driver since a driver can have different interrupt handlers for different ccw devices (multi-subchannel drivers).

struct ccw_driver: device driver for channel attached devices

Definition

struct ccw_driver {
  struct ccw_device_id *ids;
  int (*probe) (struct ccw_device *);
  void (*remove) (struct ccw_device *);
  int (*set_online) (struct ccw_device *);
  int (*set_offline) (struct ccw_device *);
  int (*notify) (struct ccw_device *, int);
  void (*path_event) (struct ccw_device *, int *);
  void (*shutdown) (struct ccw_device *);
  int (*prepare) (struct ccw_device *);
  void (*complete) (struct ccw_device *);
  int (*freeze)(struct ccw_device *);
  int (*thaw) (struct ccw_device *);
  int (*restore)(struct ccw_device *);
  enum uc_todo (*uc_handler) (struct ccw_device *, struct irb *);
  struct device_driver driver;
  enum interruption_class int_class;
};

Members

ids: ids supported by this driver
probe: function called on probe
remove: function called on remove
set_online: called when setting device online
set_offline: called when setting device offline
notify: notify driver of device state changes
path_event: notify driver of channel path events
shutdown: called at device shutdown
prepare: prepare for pm state transition
complete: undo work done in prepare
freeze: callback for freezing during hibernation snapshotting
thaw: undo work done in freeze
restore: callback for restoring after hibernation
uc_handler: callback for unit check handler
driver: embedded device driver structure
int_class: interruption class to use for accounting interrupts

int ccw_device_set_offline(struct ccw_device *cdev)¶: disable a ccw device for I/O

Parameters

struct ccw_device * cdev: target ccw device

Description

This function calls the driver’s set_offline() function for cdev, if given, and then disables cdev.

Return

0 on success and a negative error value on failure.

Context

enabled, ccw device lock not held

int ccw_device_set_online(struct ccw_device *cdev)¶: enable a ccw device for I/O

Parameters

struct ccw_device * cdev: target ccw device

Description

This function first enables cdev and then calls the driver’s set_online() function for cdev, if given. If set_online() returns an error, cdev is disabled again.

Return

0 on success and a negative error value on failure.

Context

enabled, ccw device lock not held

struct ccw_device *get_ccwdev_by_dev_id(struct ccw_dev_id *dev_id)¶: obtain device from a ccw device id

Parameters

struct ccw_dev_id * dev_id: id of the device to be searched

Description

This function searches all devices attached to the ccw bus for a device matching dev_id.

Return

If a device is found its reference count is increased and returned; else NULL is returned.

struct ccw_device *get_ccwdev_by_busid(struct ccw_driver *cdrv, const char *bus_id)¶: obtain device from a bus id

Parameters

struct ccw_driver * cdrv: driver the device is owned by
const char * bus_id: bus id of the device to be searched

Description

This function searches all devices owned by cdrv for a device with a bus id matching bus_id.

Return

If a match is found, its reference count of the found device is increased and it is returned; else NULL is returned.

int ccw_driver_register(struct ccw_driver *cdriver)¶: register a ccw driver

Parameters

struct ccw_driver * cdriver: driver to be registered

Description

This function is mainly a wrapper around driver_register().

Return

0 on success and a negative error value on failure.

void ccw_driver_unregister(struct ccw_driver *cdriver)¶: deregister a ccw driver

Parameters

struct ccw_driver * cdriver: driver to be deregistered

Description

This function is mainly a wrapper around driver_unregister().

int ccw_device_siosl(struct ccw_device *cdev)¶: initiate logging

Parameters

struct ccw_device * cdev: ccw device

Description

This function is used to invoke model-dependent logging within the channel subsystem.

int ccw_device_set_options_mask(struct ccw_device *cdev, unsigned long flags)¶: set some options and unset the rest

Parameters

struct ccw_device * cdev: device for which the options are to be set
unsigned long flags: options to be set

Description

All flags specified in flags are set, all flags not specified in flags are cleared.

Return

0 on success, -EINVAL on an invalid flag combination.

int ccw_device_set_options(struct ccw_device *cdev, unsigned long flags)¶: set some options

Parameters

struct ccw_device * cdev: device for which the options are to be set
unsigned long flags: options to be set

Description

All flags specified in flags are set, the remainder is left untouched.

Return

0 on success, -EINVAL if an invalid flag combination would ensue.

void ccw_device_clear_options(struct ccw_device *cdev, unsigned long flags)¶: clear some options

Parameters

struct ccw_device * cdev: device for which the options are to be cleared
unsigned long flags: options to be cleared

Description

All flags specified in flags are cleared, the remainder is left untouched.

int ccw_device_is_pathgroup(struct ccw_device *cdev)¶: determine if paths to this device are grouped

Parameters

struct ccw_device * cdev: ccw device

Description

Return non-zero if there is a path group, zero otherwise.

int ccw_device_is_multipath(struct ccw_device *cdev)¶: determine if device is operating in multipath mode

Parameters

struct ccw_device * cdev: ccw device

Description

Return non-zero if device is operating in multipath mode, zero otherwise.

int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm)¶: terminate I/O request processing

Parameters

struct ccw_device * cdev: target ccw device
unsigned long intparm: interruption parameter to be returned upon conclusion of csch

Description

ccw_device_clear() calls csch on cdev’s subchannel.

Return

0 on success, -ENODEV on device not operational, -EINVAL on invalid device state.

Context

Interrupts disabled, ccw device lock held

int ccw_device_start_timeout_key(struct ccw_device *cdev, struct ccw1 *cpa, unsigned long intparm, __u8 lpm, __u8 key, unsigned long flags, int expires)¶: start a s390 channel program with timeout and key

Parameters

struct ccw_device * cdev: target ccw device
struct ccw1 * cpa: logical start address of channel program
unsigned long intparm: user specific interruption parameter; will be presented back to cdev’s interrupt handler. Allows a device driver to associate the interrupt with a particular I/O request.
__u8 lpm: defines the channel path to be used for a specific I/O request. A value of 0 will make cio use the opm.
__u8 key: storage key to be used for the I/O
unsigned long flags: additional flags; defines the action to be performed for I/O processing.
int expires: timeout value in jiffies

Description

Start a S/390 channel program. When the interrupt arrives, the IRQ handler is called, either immediately, delayed (dev-end missing, or sense required) or never (no IRQ handler registered). This function notifies the device driver if the channel program has not completed during the time specified by expires. If a timeout occurs, the channel program is terminated via xsch, hsch or csch, and the device’s interrupt handler will be called with an irb containing ERR_PTR(-ETIMEDOUT). The interruption handler will echo back the intparm specified here, unless another interruption parameter is specified by a subsequent invocation of ccw_device_halt() or ccw_device_clear().

Return

0, if the operation was successful; -EBUSY, if the device is busy, or status pending; -EACCES, if no path specified in lpm is operational; -ENODEV, if the device is not operational.

Context

Interrupts disabled, ccw device lock held

int ccw_device_start_key(struct ccw_device *cdev, struct ccw1 *cpa, unsigned long intparm, __u8 lpm, __u8 key, unsigned long flags)¶: start a s390 channel program with key

Parameters

struct ccw_device * cdev: target ccw device
struct ccw1 * cpa: logical start address of channel program
unsigned long intparm: user specific interruption parameter; will be presented back to cdev’s interrupt handler. Allows a device driver to associate the interrupt with a particular I/O request.
__u8 lpm: defines the channel path to be used for a specific I/O request. A value of 0 will make cio use the opm.
__u8 key: storage key to be used for the I/O
unsigned long flags: additional flags; defines the action to be performed for I/O processing.

Description

Start a S/390 channel program. When the interrupt arrives, the IRQ handler is called, either immediately, delayed (dev-end missing, or sense required) or never (no IRQ handler registered). The interruption handler will echo back the intparm specified here, unless another interruption parameter is specified by a subsequent invocation of ccw_device_halt() or ccw_device_clear().

Return

0, if the operation was successful; -EBUSY, if the device is busy, or status pending; -EACCES, if no path specified in lpm is operational; -ENODEV, if the device is not operational.

Context

Interrupts disabled, ccw device lock held

int ccw_device_start(struct ccw_device *cdev, struct ccw1 *cpa, unsigned long intparm, __u8 lpm, unsigned long flags)¶: start a s390 channel program

Parameters

struct ccw_device * cdev: target ccw device
struct ccw1 * cpa: logical start address of channel program
unsigned long intparm: user specific interruption parameter; will be presented back to cdev’s interrupt handler. Allows a device driver to associate the interrupt with a particular I/O request.
__u8 lpm: defines the channel path to be used for a specific I/O request. A value of 0 will make cio use the opm.
unsigned long flags: additional flags; defines the action to be performed for I/O processing.

Description

Start a S/390 channel program. When the interrupt arrives, the IRQ handler is called, either immediately, delayed (dev-end missing, or sense required) or never (no IRQ handler registered). The interruption handler will echo back the intparm specified here, unless another interruption parameter is specified by a subsequent invocation of ccw_device_halt() or ccw_device_clear().

Return

0, if the operation was successful; -EBUSY, if the device is busy, or status pending; -EACCES, if no path specified in lpm is operational; -ENODEV, if the device is not operational.

Context

Interrupts disabled, ccw device lock held

int ccw_device_start_timeout(struct ccw_device *cdev, struct ccw1 *cpa, unsigned long intparm, __u8 lpm, unsigned long flags, int expires)¶: start a s390 channel program with timeout

Parameters

struct ccw_device * cdev: target ccw device
struct ccw1 * cpa: logical start address of channel program
unsigned long intparm: user specific interruption parameter; will be presented back to cdev’s interrupt handler. Allows a device driver to associate the interrupt with a particular I/O request.
__u8 lpm: defines the channel path to be used for a specific I/O request. A value of 0 will make cio use the opm.
unsigned long flags: additional flags; defines the action to be performed for I/O processing.
int expires: timeout value in jiffies

Description

Start a S/390 channel program. When the interrupt arrives, the IRQ handler is called, either immediately, delayed (dev-end missing, or sense required) or never (no IRQ handler registered). This function notifies the device driver if the channel program has not completed during the time specified by expires. If a timeout occurs, the channel program is terminated via xsch, hsch or csch, and the device’s interrupt handler will be called with an irb containing ERR_PTR(-ETIMEDOUT). The interruption handler will echo back the intparm specified here, unless another interruption parameter is specified by a subsequent invocation of ccw_device_halt() or ccw_device_clear().

Return

0, if the operation was successful; -EBUSY, if the device is busy, or status pending; -EACCES, if no path specified in lpm is operational; -ENODEV, if the device is not operational.

Context

Interrupts disabled, ccw device lock held

int ccw_device_halt(struct ccw_device *cdev, unsigned long intparm)¶: halt I/O request processing

Parameters

struct ccw_device * cdev: target ccw device
unsigned long intparm: interruption parameter to be returned upon conclusion of hsch

Description

ccw_device_halt() calls hsch on cdev’s subchannel. The interruption handler will echo back the intparm specified here, unless another interruption parameter is specified by a subsequent invocation of ccw_device_clear().

Return

0 on success, -ENODEV on device not operational, -EINVAL on invalid device state, -EBUSY on device busy or interrupt pending.

Context

Interrupts disabled, ccw device lock held

int ccw_device_resume(struct ccw_device *cdev)¶: resume channel program execution

Parameters

struct ccw_device * cdev: target ccw device

Description

ccw_device_resume() calls rsch on cdev’s subchannel.

Return

0 on success, -ENODEV on device not operational, -EINVAL on invalid device state, -EBUSY on device busy or interrupt pending.

Context

Interrupts disabled, ccw device lock held

struct ciw *ccw_device_get_ciw(struct ccw_device *cdev, __u32 ct)¶: Search for CIW command in extended sense data.

Parameters

struct ccw_device * cdev: ccw device to inspect
__u32 ct: command type to look for

Description

During SenseID, command information words (CIWs) describing special commands available to the device may have been stored in the extended sense data. This function searches for CIWs of a specified command type in the extended sense data.

Return

NULL if no extended sense data has been stored or if no CIW of the specified command type could be found, else a pointer to the CIW of the specified command type.

__u8 ccw_device_get_path_mask(struct ccw_device *cdev)¶: get currently available paths

Parameters

struct ccw_device * cdev: ccw device to be queried

Return

0 if no subchannel for the device is available, else the mask of currently available paths for the ccw device’s subchannel.

struct channel_path_desc_fmt0 *ccw_device_get_chp_desc(struct ccw_device *cdev, int chp_idx)¶: return newly allocated channel-path descriptor

Parameters

struct ccw_device * cdev: device to obtain the descriptor for
int chp_idx: index of the channel path

Description

On success return a newly allocated copy of the channel-path description data associated with the given channel path. Return NULL on error.

u8 *ccw_device_get_util_str(struct ccw_device *cdev, int chp_idx)¶: return newly allocated utility strings

Parameters

struct ccw_device * cdev: device to obtain the utility strings for
int chp_idx: index of the channel path

Description

On success return a newly allocated copy of the utility strings associated with the given channel path. Return NULL on error.

void ccw_device_get_id(struct ccw_device *cdev, struct ccw_dev_id *dev_id)¶: obtain a ccw device id

Parameters

struct ccw_device * cdev: device to obtain the id for
struct ccw_dev_id * dev_id: where to fill in the values

int ccw_device_tm_start_timeout_key(struct ccw_device *cdev, struct tcw *tcw, unsigned long intparm, u8 lpm, u8 key, int expires)¶: perform start function

Parameters

struct ccw_device * cdev: ccw device on which to perform the start function
struct tcw * tcw: transport-command word to be started
unsigned long intparm: user defined parameter to be passed to the interrupt handler
u8 lpm: mask of paths to use
u8 key: storage key to use for storage access
int expires: time span in jiffies after which to abort request

Description

Start the tcw on the given ccw device. Return zero on success, non-zero otherwise.

int ccw_device_tm_start_key(struct ccw_device *cdev, struct tcw *tcw, unsigned long intparm, u8 lpm, u8 key)¶: perform start function

Parameters

struct ccw_device * cdev: ccw device on which to perform the start function
struct tcw * tcw: transport-command word to be started
unsigned long intparm: user defined parameter to be passed to the interrupt handler
u8 lpm: mask of paths to use
u8 key: storage key to use for storage access

Description

Start the tcw on the given ccw device. Return zero on success, non-zero otherwise.

int ccw_device_tm_start(struct ccw_device *cdev, struct tcw *tcw, unsigned long intparm, u8 lpm)¶: perform start function

Parameters

struct ccw_device * cdev: ccw device on which to perform the start function
struct tcw * tcw: transport-command word to be started
unsigned long intparm: user defined parameter to be passed to the interrupt handler
u8 lpm: mask of paths to use

Description

Start the tcw on the given ccw device. Return zero on success, non-zero otherwise.

int ccw_device_tm_start_timeout(struct ccw_device *cdev, struct tcw *tcw, unsigned long intparm, u8 lpm, int expires)¶: perform start function

Parameters

struct ccw_device * cdev: ccw device on which to perform the start function
struct tcw * tcw: transport-command word to be started
unsigned long intparm: user defined parameter to be passed to the interrupt handler
u8 lpm: mask of paths to use
int expires: time span in jiffies after which to abort request

Description

Start the tcw on the given ccw device. Return zero on success, non-zero otherwise.

int ccw_device_get_mdc(struct ccw_device *cdev, u8 mask)¶: accumulate max data count

Parameters

struct ccw_device * cdev: ccw device for which the max data count is accumulated
u8 mask: mask of paths to use

Description

Return the number of 64K-bytes blocks all paths at least support for a transport command. Return value 0 indicates failure.

int ccw_device_tm_intrg(struct ccw_device *cdev)¶: perform interrogate function

Parameters

struct ccw_device * cdev: ccw device on which to perform the interrogate function

Description

Perform an interrogate function on the given ccw device. Return zero on success, non-zero otherwise.

void ccw_device_get_schid(struct ccw_device *cdev, struct subchannel_id *schid)¶: obtain a subchannel id

Parameters

struct ccw_device * cdev: device to obtain the id for
struct subchannel_id * schid: where to fill in the values

The channel-measurement facility¶

The channel-measurement facility provides a means to collect measurement data which is made available by the channel subsystem for each channel attached device.

struct cmbdata: channel measurement block data for user space

Definition

struct cmbdata {
  __u64 size;
  __u64 elapsed_time;
  __u64 ssch_rsch_count;
  __u64 sample_count;
  __u64 device_connect_time;
  __u64 function_pending_time;
  __u64 device_disconnect_time;
  __u64 control_unit_queuing_time;
  __u64 device_active_only_time;
  __u64 device_busy_time;
  __u64 initial_command_response_time;
};

Members

size: size of the stored data
elapsed_time: time since last sampling
ssch_rsch_count: number of ssch and rsch
sample_count: number of samples
device_connect_time: time of device connect
function_pending_time: time of function pending
device_disconnect_time: time of device disconnect
control_unit_queuing_time: time of control unit queuing
device_active_only_time: time of device active only
device_busy_time: time of device busy (ext. format)
initial_command_response_time: initial command response time (ext. format)

Description

All values are stored as 64 bit for simplicity, especially in 32 bit emulation mode. All time values are normalized to nanoseconds. Currently, two formats are known, which differ by the size of this structure, i.e. the last two members are only set when the extended channel measurement facility (first shipped in z990 machines) is activated. Potentially, more fields could be added, which would result in a new ioctl number.

int enable_cmf(struct ccw_device *cdev)¶: switch on the channel measurement for a specific device

Parameters

struct ccw_device * cdev: The ccw device to be enabled

Description

Enable channel measurements for cdev. If this is called on a device for which channel measurement is already enabled a reset of the measurement data is triggered.

Return

0 for success or a negative error value.

Context

non-atomic

int disable_cmf(struct ccw_device *cdev)¶: switch off the channel measurement for a specific device

Parameters

struct ccw_device * cdev: The ccw device to be disabled

Return

0 for success or a negative error value.

Context

non-atomic

u64 cmf_read(struct ccw_device *cdev, int index)¶: read one value from the current channel measurement block

Parameters

struct ccw_device * cdev: the channel to be read
int index: the index of the value to be read

Return

The value read or 0 if the value cannot be read.

Context

any

int cmf_readall(struct ccw_device *cdev, struct cmbdata *data)¶: read the current channel measurement block

Parameters

struct ccw_device * cdev: the channel to be read
struct cmbdata * data: a pointer to a data block that will be filled

Return

0 on success, a negative error value otherwise.

Context

any

The ccwgroup bus¶

The ccwgroup bus only contains artificial devices, created by the user. Many networking devices (e.g. qeth) are in fact composed of several ccw devices (like read, write and data channel for qeth). The ccwgroup bus provides a mechanism to create a meta-device which contains those ccw devices as slave devices and can be associated with the netdevice.

ccw group devices¶

struct ccwgroup_device: ccw group device

Definition

struct ccwgroup_device {
  enum {
    CCWGROUP_OFFLINE,
    CCWGROUP_ONLINE,
  } state;
  unsigned int count;
  struct device   dev;
  struct work_struct ungroup_work;
  struct ccw_device *cdev[0];
};

Members

state: online/offline state
count: number of attached slave devices
dev: embedded device structure
ungroup_work: work to be done when a ccwgroup notifier has action type BUS_NOTIFY_UNBIND_DRIVER
cdev: variable number of slave devices, allocated as needed

struct ccwgroup_driver: driver for ccw group devices

Definition

struct ccwgroup_driver {
  int (*setup) (struct ccwgroup_device *);
  void (*remove) (struct ccwgroup_device *);
  int (*set_online) (struct ccwgroup_device *);
  int (*set_offline) (struct ccwgroup_device *);
  void (*shutdown)(struct ccwgroup_device *);
  int (*prepare) (struct ccwgroup_device *);
  void (*complete) (struct ccwgroup_device *);
  int (*freeze)(struct ccwgroup_device *);
  int (*thaw) (struct ccwgroup_device *);
  int (*restore)(struct ccwgroup_device *);
  struct device_driver driver;
  struct ccw_driver *ccw_driver;
};

Members

setup: function called during device creation to setup the device
remove: function called on remove
set_online: function called when device is set online
set_offline: function called when device is set offline
shutdown: function called when device is shut down
prepare: prepare for pm state transition
complete: undo work done in prepare
freeze: callback for freezing during hibernation snapshotting
thaw: undo work done in freeze
restore: callback for restoring after hibernation
driver: embedded driver structure
ccw_driver: supported ccw_driver (optional)

int ccwgroup_set_online(struct ccwgroup_device *gdev)¶: enable a ccwgroup device

Parameters

struct ccwgroup_device * gdev: target ccwgroup device

Description

This function attempts to put the ccwgroup device into the online state.

Return

0 on success and a negative error value on failure.

int ccwgroup_set_offline(struct ccwgroup_device *gdev)¶: disable a ccwgroup device

Parameters

struct ccwgroup_device * gdev: target ccwgroup device

Description

This function attempts to put the ccwgroup device into the offline state.

Return

0 on success and a negative error value on failure.

int ccwgroup_create_dev(struct device *parent, struct ccwgroup_driver *gdrv, int num_devices, const char *buf)¶: create and register a ccw group device

Parameters

struct device * parent: parent device for the new device
struct ccwgroup_driver * gdrv: driver for the new group device
int num_devices: number of slave devices
const char * buf: buffer containing comma separated bus ids of slave devices

Description

Create and register a new ccw group device as a child of parent. Slave devices are obtained from the list of bus ids given in buf.

Return

0 on success and an error code on failure.

Context

non-atomic

int ccwgroup_driver_register(struct ccwgroup_driver *cdriver)¶: register a ccw group driver

Parameters

struct ccwgroup_driver * cdriver: driver to be registered

Description

This function is mainly a wrapper around driver_register().

void ccwgroup_driver_unregister(struct ccwgroup_driver *cdriver)¶: deregister a ccw group driver

Parameters

struct ccwgroup_driver * cdriver: driver to be deregistered

Description

This function is mainly a wrapper around driver_unregister().

struct ccwgroup_device *get_ccwgroupdev_by_busid(struct ccwgroup_driver *gdrv, char *bus_id)¶: obtain device from a bus id

Parameters

struct ccwgroup_driver * gdrv: driver the device is owned by
char * bus_id: bus id of the device to be searched

Description

This function searches all devices owned by gdrv for a device with a bus id matching bus_id.

Return

If a match is found, its reference count of the found device is increased and it is returned; else NULL is returned.

int ccwgroup_probe_ccwdev(struct ccw_device *cdev)¶: probe function for slave devices

Parameters

struct ccw_device * cdev: ccw device to be probed

Description

This is a dummy probe function for ccw devices that are slave devices in a ccw group device.

Return

always 0

void ccwgroup_remove_ccwdev(struct ccw_device *cdev)¶: remove function for slave devices

Parameters

struct ccw_device * cdev: ccw device to be removed

Description

This is a remove function for ccw devices that are slave devices in a ccw group device. It sets the ccw device offline and also deregisters the embedding ccw group device.

Generic interfaces¶

The following section contains interfaces in use not only by drivers dealing with ccw devices, but drivers for various other s390 hardware as well.

Adapter interrupts¶

The common I/O layer provides helper functions for dealing with adapter interrupts and interrupt vectors.

int register_adapter_interrupt(struct airq_struct *airq)¶: register adapter interrupt handler

Parameters

struct airq_struct * airq: pointer to adapter interrupt descriptor

Description

Returns 0 on success, or -EINVAL.

void unregister_adapter_interrupt(struct airq_struct *airq)¶: unregister adapter interrupt handler

Parameters

struct airq_struct * airq: pointer to adapter interrupt descriptor

struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags)¶: create an interrupt vector

Parameters

unsigned long bits: number of bits in the interrupt vector
unsigned long flags: allocation flags

Description

Returns a pointer to an interrupt vector structure

void airq_iv_release(struct airq_iv *iv)¶: release an interrupt vector

Parameters

struct airq_iv * iv: pointer to interrupt vector structure

unsigned long airq_iv_alloc(struct airq_iv *iv, unsigned long num)¶: allocate irq bits from an interrupt vector

Parameters

struct airq_iv * iv: pointer to an interrupt vector structure
unsigned long num: number of consecutive irq bits to allocate

Description

Returns the bit number of the first irq in the allocated block of irqs, or -1UL if no bit is available or the AIRQ_IV_ALLOC flag has not been specified

void airq_iv_free(struct airq_iv *iv, unsigned long bit, unsigned long num)¶: free irq bits of an interrupt vector

Parameters

struct airq_iv * iv: pointer to interrupt vector structure
unsigned long bit: number of the first irq bit to free
unsigned long num: number of consecutive irq bits to free

unsigned long airq_iv_scan(struct airq_iv *iv, unsigned long start, unsigned long end)¶: scan interrupt vector for non-zero bits

Parameters

struct airq_iv * iv: pointer to interrupt vector structure
unsigned long start: bit number to start the search
unsigned long end: bit number to end the search

Description

Returns the bit number of the next non-zero interrupt bit, or -1UL if the scan completed without finding any more any non-zero bits.

Writing s390 channel device drivers¶

Introduction¶

The css bus¶

The ccw bus¶

I/O functions for channel-attached devices¶

ccw devices¶

The channel-measurement facility¶

The ccwgroup bus¶

ccw group devices¶

Generic interfaces¶

Adapter interrupts¶

The Linux Kernel

Navigation

Related Topics