vme.rst 10.4 KB
Newer Older
1 2
VME Device Drivers
3 4

Driver registration
6 7 8

As with other subsystems within the Linux kernel, VME device drivers register
with the VME subsystem, typically called from the devices init routine.  This is
achieved via a call to :c:func:`vme_register_driver`.

11 12 13
A pointer to a structure of type :c:type:`struct vme_driver <vme_driver>` must
be provided to the registration function. Along with the maximum number of
devices your driver is able to support.

15 16 17
At the minimum, the '.name', '.match' and '.probe' elements of
:c:type:`struct vme_driver <vme_driver>` should be correctly set. The '.name'
element is a pointer to a string holding the device driver's name.

19 20
The '.match' function allows control over which VME devices should be registered
with the driver. The match function should return 1 if a device should be
21 22
probed and 0 otherwise. This example match function (from vme_user.c) limits
the number of devices probed to one:

24 25
.. code-block:: c

26 27 28 29 30 31 32 33
	#define USER_BUS_MAX	1
	static int vme_user_match(struct vme_dev *vdev)
		if (vdev->id.num >= USER_BUS_MAX)
			return 0;
		return 1;

The '.probe' element should contain a pointer to the probe routine. The
36 37
probe routine is passed a :c:type:`struct vme_dev <vme_dev>` pointer as an

39 40 41
Here, the 'num' field refers to the sequential device ID for this specific
driver. The bridge number (or bus number) can be accessed using

43 44 45
A function is also provided to unregister the driver from the VME core called
:c:func:`vme_unregister_driver` and should usually be called from the device
driver's exit routine.
46 47 48

Resource management

51 52 53 54 55
Once a driver has registered with the VME core the provided match routine will
be called the number of times specified during the registration. If a match
succeeds, a non-zero value should be returned. A zero return value indicates
failure. For all successful matches, the probe routine of the corresponding
driver is called. The probe routine is passed a pointer to the devices
56 57 58
device structure. This pointer should be saved, it will be required for
requesting VME resources.

59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76
The driver can request ownership of one or more master windows
(:c:func:`vme_master_request`), slave windows (:c:func:`vme_slave_request`)
and/or dma channels (:c:func:`vme_dma_request`). Rather than allowing the device
driver to request a specific window or DMA channel (which may be used by a
different driver) the API allows a resource to be assigned based on the required
attributes of the driver in question. For slave windows these attributes are
split into the VME address spaces that need to be accessed in 'aspace' and VME
bus cycle types required in 'cycle'. Master windows add a further set of
attributes in 'width' specifying the required data transfer widths. These
attributes are defined as bitmasks and as such any combination of the
attributes can be requested for a single window, the core will assign a window
that meets the requirements, returning a pointer of type vme_resource that
should be used to identify the allocated resource when it is used. For DMA
controllers, the request function requires the potential direction of any
transfers to be provided in the route attributes. This is typically VME-to-MEM
and/or MEM-to-VME, though some hardware can support VME-to-VME and MEM-to-MEM
transfers as well as test pattern generation. If an unallocated window fitting
the requirements can not be found a NULL pointer will be returned.
77 78

Functions are also provided to free window allocations once they are no longer
79 80 81
required. These functions (:c:func:`vme_master_free`, :c:func:`vme_slave_free`
and :c:func:`vme_dma_free`) should be passed the pointer to the resource
provided during resource allocation.
82 83 84

Master windows
86 87

Master windows provide access from the local processor[s] out onto the VME bus.
The number of windows available and the available access modes is dependent on
89 90 91 92
the underlying chipset. A window must be configured before it can be used.

Master window configuration

95 96 97
Once a master window has been assigned :c:func:`vme_master_set` can be used to
configure it and :c:func:`vme_master_get` to retrieve the current settings. The
address spaces, transfer widths and cycle types are the same as described
98 99 100 101 102
under resource management, however some of the options are mutually exclusive.
For example, only one address space may be specified.

Master window access

105 106
The function :c:func:`vme_master_read` can be used to read from and
:c:func:`vme_master_write` used to write to configured master windows.

108 109 110
In addition to simple reads and writes, :c:func:`vme_master_rmw` is provided to
do a read-modify-write transaction. Parts of a VME window can also be mapped
into user space memory using :c:func:`vme_master_mmap`.

112 113

Slave windows
115 116 117

Slave windows provide devices on the VME bus access into mapped portions of the
local memory. The number of windows available and the access modes that can be
used is dependent on the underlying chipset. A window must be configured before
119 120 121 122
it can be used.

Slave window configuration

125 126
Once a slave window has been assigned :c:func:`vme_slave_set` can be used to
configure it and :c:func:`vme_slave_get` to retrieve the current settings.
127 128 129 130 131 132 133

The address spaces, transfer widths and cycle types are the same as described
under resource management, however some of the options are mutually exclusive.
For example, only one address space may be specified.

Slave window buffer allocation

136 137 138 139 140 141
Functions are provided to allow the user to allocate
(:c:func:`vme_alloc_consistent`) and free (:c:func:`vme_free_consistent`)
contiguous buffers which will be accessible by the VME bridge. These functions
do not have to be used, other methods can be used to allocate a buffer, though
care must be taken to ensure that they are contiguous and accessible by the VME
142 143 144

Slave window access
146 147 148 149 150 151

Slave windows map local memory onto the VME bus, the standard methods for
accessing memory should be used.

DMA channels
153 154 155 156 157 158 159 160

The VME DMA transfer provides the ability to run link-list DMA transfers. The
API introduces the concept of DMA lists. Each DMA list is a link-list which can
be passed to a DMA controller. Multiple lists can be created, extended,
executed, reused and destroyed.

List Management

163 164 165 166
The function :c:func:`vme_new_dma_list` is provided to create and
:c:func:`vme_dma_list_free` to destroy DMA lists. Execution of a list will not
automatically destroy the list, thus enabling a list to be reused for repetitive
167 168 169

List Population

An item can be added to a list using :c:func:`vme_dma_list_add` (the source and
destination attributes need to be created before calling this function, this is
covered under "Transfer Attributes").

176 177 178
.. note::

	The detailed attributes of the transfers source and destination
179 180 181 182 183
	are not checked until an entry is added to a DMA list, the request
	for a DMA channel purely checks the directions in which the
	controller is expected to transfer data. As a result it is
	possible for this call to return an error, for example if the
	source or destination is in an unsupported VME address space.
184 185

Transfer Attributes
187 188 189 190 191 192

The attributes for the source and destination are handled separately from adding
an item to a list. This is due to the diverse attributes required for each type
of source and destination. There are functions to create attributes for PCI, VME
and pattern sources and destinations (where appropriate):

193 194 195
 - PCI source or destination: :c:func:`vme_dma_pci_attribute`
 - VME source or destination: :c:func:`vme_dma_vme_attribute`
 - Pattern source: :c:func:`vme_dma_pattern_attribute`

197 198
The function :c:func:`vme_dma_free_attribute` should be used to free an
199 200 201

List Execution

204 205
The function :c:func:`vme_dma_list_exec` queues a list for execution and will
return once the list has been executed.
206 207 208

210 211 212 213 214 215 216

The VME API provides functions to attach and detach callbacks to specific VME
level and status ID combinations and for the generation of VME interrupts with
specific VME level and status IDs.

Attaching Interrupt Handlers

219 220 221 222 223 224 225
The function :c:func:`vme_irq_request` can be used to attach and
:c:func:`vme_irq_free` to free a specific VME level and status ID combination.
Any given combination can only be assigned a single callback function. A void
pointer parameter is provided, the value of which is passed to the callback
function, the use of this pointer is user undefined. The callback parameters are
as follows. Care must be taken in writing a callback function, callback
functions run in interrupt context:

227 228
.. code-block:: c

229 230 231 232
	void callback(int level, int statid, void *priv);

Interrupt Generation

235 236
The function :c:func:`vme_irq_generate` can be used to generate a VME interrupt
at a given VME level and VME status ID.
237 238 239

Location monitors
241 242 243 244 245 246

The VME API provides the following functionality to configure the location

Location Monitor Management

249 250 251 252 253
The function :c:func:`vme_lm_request` is provided to request the use of a block
of location monitors and :c:func:`vme_lm_free` to free them after they are no
longer required. Each block may provide a number of location monitors,
monitoring adjacent locations. The function :c:func:`vme_lm_count` can be used
to determine how many locations are provided.
254 255 256

Location Monitor Configuration

259 260 261 262
Once a bank of location monitors has been allocated, the function
:c:func:`vme_lm_set` is provided to configure the location and mode of the
location monitor. The function :c:func:`vme_lm_get` can be used to retrieve
existing settings.
263 264 265

Location Monitor Use

268 269 270 271
The function :c:func:`vme_lm_attach` enables a callback to be attached and
:c:func:`vme_lm_detach` allows on to be detached from each location monitor
location. Each location monitor can monitor a number of adjacent locations. The
callback function is declared as follows.

273 274
.. code-block:: c

	void callback(void *data);
276 277 278

Slot Detection

The function :c:func:`vme_slot_num` returns the slot ID of the provided bridge.
282 283 284

Bus Detection

The function :c:func:`vme_bus_num` returns the bus ID of the provided bridge.
288 289

290 291 292 293 294

.. kernel-doc:: include/linux/vme.h

296 297
.. kernel-doc:: drivers/vme/vme.c