* The interrupt handlers must be adapted to use a ccw_device as argument.
Moreover, they don't return a devstat, but an irb.
* Before initiating an io, the options must be set via ccw_device_set_options().
-
-read_dev_chars()
- read device characteristics
-
-read_conf_data()
-read_conf_data_lpm()
- read configuration data.
+* Instead of calling read_dev_chars()/read_conf_data(), the driver issues
+ the channel program and handles the interrupt itself.
ccw_device_get_ciw()
get commands from extended sense data.
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.
has to call every single device driver registered on this IRQ in order to
determine the device driver owning the device that raised the interrupt.
-In order not to introduce a new I/O concept to the common Linux code,
-Linux/390 preserves the IRQ concept and semantically maps the ESA/390
-subchannels to Linux as IRQs. This allows Linux/390 to support up to 64k
-different IRQs, uniquely representing a single device each.
-
Up to kernel 2.4, Linux/390 used to provide interfaces via the IRQ (subchannel).
For internal use of the common I/O layer, these are still there. However,
device drivers should use the new calling interface via the ccw_device only.
support using the information saved in the struct ccw_device given to them.
This methods implies that Linux/390 doesn't require to probe for free (not
armed) interrupt request lines (IRQs) to drive its devices with. Where
-applicable, the device drivers can use the read_dev_chars() to retrieve device
-characteristics. This can be done without having to request device ownership
-previously.
+applicable, the device drivers can use issue the READ DEVICE CHARACTERISTICS
+ccw to retrieve device characteristics in its online routine.
In order to allow for easy I/O initiation the CDS layer provides a
ccw_device_start() interface that takes a device specific channel program (one
also covered by ccw_device_halt().
-read_dev_chars() - Read Device Characteristics
-
-This routine returns the characteristics for the device specified.
-
-The function is meant to be called with the device already enabled; that is,
-at earliest during set_online() processing.
-
-The ccw_device must not be locked prior to calling read_dev_chars().
-
-The function may be called enabled or disabled.
-
-int read_dev_chars(struct ccw_device *cdev, void **buffer, int length );
-
-cdev - the ccw_device the information is requested for.
-buffer - pointer to a buffer pointer. The buffer pointer itself
- must contain a valid buffer area.
-length - length of the buffer provided.
-
-The read_dev_chars() function returns :
-
- 0 - successful completion
--ENODEV - cdev invalid
--EINVAL - an invalid parameter was detected, or the function was called early.
--EBUSY - an irrecoverable I/O error occurred or the device is not
- operational.
-
-
-read_conf_data(), read_conf_data_lpm() - Read Configuration Data
-
-Retrieve the device dependent configuration data. Please have a look at your
-device dependent I/O commands for the device specific layout of the node
-descriptor elements. read_conf_data_lpm() will retrieve the configuration data
-for a specific path.
-
-The function is meant to be called with the device already enabled; that is,
-at earliest during set_online() processing.
-
-The function may be called enabled or disabled, but the device must not be
-locked
-
-int read_conf_data(struct ccw_device, void **buffer, int *length);
-int read_conf_data_lpm(struct ccw_device, void **buffer, int *length, __u8 lpm);
-
-cdev - the ccw_device the data is requested for.
-buffer - Pointer to a buffer pointer. The read_conf_data() routine
- will allocate a buffer and initialize the buffer pointer
- accordingly. It's the device driver's responsibility to
- release the kernel memory if no longer needed.
-length - Length of the buffer allocated and retrieved.
-lpm - Logical path mask to be used for retrieving the data. If
- zero the data is retrieved on the next path available.
-
-The read_conf_data() function returns :
- 0 - Successful completion
--ENODEV - cdev invalid.
--EINVAL - An invalid parameter was detected, or the function was called early.
--EIO - An irrecoverable I/O error occurred or the device is
- not operational.
--ENOMEM - The read_conf_data() routine couldn't obtain storage.
--EOPNOTSUPP - The device doesn't support the read configuration
- data command.
-
-
get_ciw() - get command information word
This call enables a device driver to get information about supported commands
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.
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
projects / linux-drm-fsl-dcu.git / blobdiff