Linux/390 common device support (CDS) provides to allow for device specific
driver implementations on the IBM ESA/390 hardware platform. Those interfaces
intend to provide the functionality required by every device driver
-implementaion to allow to drive a specific hardware device on the ESA/390
+implementation to allow to drive a specific hardware device on the ESA/390
platform. Some of the interface routines are specific to Linux/390 and some
of them can be found on other Linux platforms implementations too.
Miscellaneous function prototypes, data declarations, and macro definitions
provides a unified view of the devices physically attached to the systems.
Though the ESA/390 hardware platform knows about a huge variety of different
peripheral attachments like disk devices (aka. DASDs), tapes, communication
-controllers, etc. they can all by accessed by a well defined access method and
+controllers, etc. they can all be accessed by a well defined access method and
they are presenting I/O completion a unified way : I/O interruptions. Every
single device is uniquely identified to the system by a so called subchannel,
where the ESA/390 architecture allows for 64k devices be attached.
This routine returns the characteristics for the device specified.
-The function is meant to be called with an irq handler in place; that is,
+The function is meant to be called with the device already enabled; that is,
at earliest during set_online() processing.
-While the request is processed synchronously, the device interrupt
-handler is called for final ending status. In case of error situations the
-interrupt handler may recover appropriately. The device irq handler can
-recognize the corresponding interrupts by the interruption parameter be
-0x00524443. The ccw_device must not be locked prior to calling read_dev_chars().
+The ccw_device must not be locked prior to calling read_dev_chars().
The function may be called enabled or disabled.
The ccw_device_start() function returns :
0 - successful completion or request successfully initiated
--EBUSY - The device is currently processing a previous I/O request, or ther is
+-EBUSY - The device is currently processing a previous I/O request, or there is
a status pending at the device.
-ENODEV - cdev is invalid, the device is not operational or the ccw_device is
not online.
-EIO: the common I/O layer terminated the request due to an error state
If the concurrent sense flag in the extended status word in the irb is set, the
-field irb->scsw.count describes the numer of device specific sense bytes
+field irb->scsw.count describes the number of device specific sense bytes
available in the extended control word irb->scsw.ecw[0]. No device sensing by
the device driver itself is required.
Usage Notes :
-Prior to call ccw_device_start() the device driver must assure disabled state,
-i.e. the I/O mask value in the PSW must be disabled. This can be accomplished
-by calling local_save_flags( flags). The current PSW flags are preserved and
-can be restored by local_irq_restore( flags) at a later time.
-
-If the device driver violates this rule while running in a uni-processor
-environment an interrupt might be presented prior to the ccw_device_start()
-routine returning to the device driver main path. In this case we will end in a
-deadlock situation as the interrupt handler will try to obtain the irq
-lock the device driver still owns (see below) !
-
-The driver must assure to hold the device specific lock. This can be
-accomplished by
-
-(i) spin_lock(get_ccwdev_lock(cdev)), or
-(ii) spin_lock_irqsave(get_ccwdev_lock(cdev), flags)
-
-Option (i) should be used if the calling routine is running disabled for
-I/O interrupts (see above) already. Option (ii) obtains the device gate und
-puts the CPU into I/O disabled state by preserving the current PSW flags.
+ccw_device_start() must be called disabled and with the ccw device lock held.
The device driver is allowed to issue the next ccw_device_start() call from
within its interrupt handler already. It is not required to schedule a
-bottom-half, unless an non deterministically long running error recovery procedure
+bottom-half, unless a non deterministically long running error recovery procedure
or similar needs to be scheduled. During I/O processing the Linux/390 generic
I/O device driver support has already obtained the IRQ lock, i.e. the handler
must not try to obtain it again when calling ccw_device_start() or we end in a
case all I/O interruptions are presented to the device driver until final
status is recognized.
-If a device is able to recover from asynchronosly presented I/O errors, it can
+If a device is able to recover from asynchronously presented I/O errors, it can
perform overlapping I/O using the DOIO_EARLY_NOTIFICATION flag. While some
devices always report channel-end and device-end together, with a single
interrupt, others present primary status (channel-end) when the channel is
cdev - ccw_device the resume operation is requested for
-The resume_IO() function returns:
+The ccw_device_resume() function returns:
0 - suspended channel program is resumed
-EBUSY - status pending
a halt subchannel (HSCH) I/O command. For those purposes the ccw_device_halt()
command is provided.
+ccw_device_halt() must be called disabled and with the ccw device lock held.
+
int ccw_device_halt(struct ccw_device *cdev,
unsigned long intparm);
The ccw_device_halt() function returns :
- 0 - successful completion or request successfully initiated
+ 0 - request successfully initiated
-EBUSY - the device is currently busy, or status pending.
-ENODEV - cdev invalid.
-EINVAL - The device is not operational or the ccw device is not online.
read to a network device (with or without PCI flag) a ccw_device_halt()
is required to end the pending operation.
+ccw_device_clear() - Terminage I/O Request Processing
+
+In order to terminate all I/O processing at the subchannel, the clear subchannel
+(CSCH) command is used. It can be issued via ccw_device_clear().
+
+ccw_device_clear() must be called disabled and with the ccw device lock held.
+
+int ccw_device_clear(struct ccw_device *cdev, unsigned long intparm);
+
+cdev: ccw_device the clear operation is requested for
+intparm: interruption parameter (see ccw_device_halt())
+
+The ccw_device_clear() function returns:
+
+ 0 - request successfully initiated
+-ENODEV - cdev invalid
+-EINVAL - The device is not operational or the ccw device is not online.
Miscellaneous Support Routines
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