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1VME Device Drivers2==================3 4Driver registration5-------------------6 7As with other subsystems within the Linux kernel, VME device drivers register8with the VME subsystem, typically called from the devices init routine. This is9achieved via a call to :c:func:`vme_register_driver`.10 11A pointer to a structure of type :c:type:`struct vme_driver <vme_driver>` must12be provided to the registration function. Along with the maximum number of13devices your driver is able to support.14 15At the minimum, the '.name', '.match' and '.probe' elements of16:c:type:`struct vme_driver <vme_driver>` should be correctly set. The '.name'17element is a pointer to a string holding the device driver's name.18 19The '.match' function allows control over which VME devices should be registered20with the driver. The match function should return 1 if a device should be21probed and 0 otherwise. This example match function (from vme_user.c) limits22the number of devices probed to one:23 24.. code-block:: c25 26 #define USER_BUS_MAX 127 ...28 static int vme_user_match(struct vme_dev *vdev)29 {30 if (vdev->id.num >= USER_BUS_MAX)31 return 0;32 return 1;33 }34 35The '.probe' element should contain a pointer to the probe routine. The36probe routine is passed a :c:type:`struct vme_dev <vme_dev>` pointer as an37argument.38 39Here, the 'num' field refers to the sequential device ID for this specific40driver. The bridge number (or bus number) can be accessed using41dev->bridge->num.42 43A function is also provided to unregister the driver from the VME core called44:c:func:`vme_unregister_driver` and should usually be called from the device45driver's exit routine.46 47 48Resource management49-------------------50 51Once a driver has registered with the VME core the provided match routine will52be called the number of times specified during the registration. If a match53succeeds, a non-zero value should be returned. A zero return value indicates54failure. For all successful matches, the probe routine of the corresponding55driver is called. The probe routine is passed a pointer to the devices56device structure. This pointer should be saved, it will be required for57requesting VME resources.58 59The driver can request ownership of one or more master windows60(:c:func:`vme_master_request`), slave windows (:c:func:`vme_slave_request`)61and/or dma channels (:c:func:`vme_dma_request`). Rather than allowing the device62driver to request a specific window or DMA channel (which may be used by a63different driver) the API allows a resource to be assigned based on the required64attributes of the driver in question. For slave windows these attributes are65split into the VME address spaces that need to be accessed in 'aspace' and VME66bus cycle types required in 'cycle'. Master windows add a further set of67attributes in 'width' specifying the required data transfer widths. These68attributes are defined as bitmasks and as such any combination of the69attributes can be requested for a single window, the core will assign a window70that meets the requirements, returning a pointer of type vme_resource that71should be used to identify the allocated resource when it is used. For DMA72controllers, the request function requires the potential direction of any73transfers to be provided in the route attributes. This is typically VME-to-MEM74and/or MEM-to-VME, though some hardware can support VME-to-VME and MEM-to-MEM75transfers as well as test pattern generation. If an unallocated window fitting76the requirements can not be found a NULL pointer will be returned.77 78Functions are also provided to free window allocations once they are no longer79required. These functions (:c:func:`vme_master_free`, :c:func:`vme_slave_free`80and :c:func:`vme_dma_free`) should be passed the pointer to the resource81provided during resource allocation.82 83 84Master windows85--------------86 87Master windows provide access from the local processor[s] out onto the VME bus.88The number of windows available and the available access modes is dependent on89the underlying chipset. A window must be configured before it can be used.90 91 92Master window configuration93~~~~~~~~~~~~~~~~~~~~~~~~~~~94 95Once a master window has been assigned :c:func:`vme_master_set` can be used to96configure it and :c:func:`vme_master_get` to retrieve the current settings. The97address spaces, transfer widths and cycle types are the same as described98under resource management, however some of the options are mutually exclusive.99For example, only one address space may be specified.100 101 102Master window access103~~~~~~~~~~~~~~~~~~~~104 105The function :c:func:`vme_master_read` can be used to read from and106:c:func:`vme_master_write` used to write to configured master windows.107 108In addition to simple reads and writes, :c:func:`vme_master_rmw` is provided to109do a read-modify-write transaction. Parts of a VME window can also be mapped110into user space memory using :c:func:`vme_master_mmap`.111 112 113Slave windows114-------------115 116Slave windows provide devices on the VME bus access into mapped portions of the117local memory. The number of windows available and the access modes that can be118used is dependent on the underlying chipset. A window must be configured before119it can be used.120 121 122Slave window configuration123~~~~~~~~~~~~~~~~~~~~~~~~~~124 125Once a slave window has been assigned :c:func:`vme_slave_set` can be used to126configure it and :c:func:`vme_slave_get` to retrieve the current settings.127 128The address spaces, transfer widths and cycle types are the same as described129under resource management, however some of the options are mutually exclusive.130For example, only one address space may be specified.131 132 133Slave window buffer allocation134~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~135 136Functions are provided to allow the user to allocate137(:c:func:`vme_alloc_consistent`) and free (:c:func:`vme_free_consistent`)138contiguous buffers which will be accessible by the VME bridge. These functions139do not have to be used, other methods can be used to allocate a buffer, though140care must be taken to ensure that they are contiguous and accessible by the VME141bridge.142 143 144Slave window access145~~~~~~~~~~~~~~~~~~~146 147Slave windows map local memory onto the VME bus, the standard methods for148accessing memory should be used.149 150 151DMA channels152------------153 154The VME DMA transfer provides the ability to run link-list DMA transfers. The155API introduces the concept of DMA lists. Each DMA list is a link-list which can156be passed to a DMA controller. Multiple lists can be created, extended,157executed, reused and destroyed.158 159 160List Management161~~~~~~~~~~~~~~~162 163The function :c:func:`vme_new_dma_list` is provided to create and164:c:func:`vme_dma_list_free` to destroy DMA lists. Execution of a list will not165automatically destroy the list, thus enabling a list to be reused for repetitive166tasks.167 168 169List Population170~~~~~~~~~~~~~~~171 172An item can be added to a list using :c:func:`vme_dma_list_add` (the source and173destination attributes need to be created before calling this function, this is174covered under "Transfer Attributes").175 176.. note::177 178 The detailed attributes of the transfers source and destination179 are not checked until an entry is added to a DMA list, the request180 for a DMA channel purely checks the directions in which the181 controller is expected to transfer data. As a result it is182 possible for this call to return an error, for example if the183 source or destination is in an unsupported VME address space.184 185Transfer Attributes186~~~~~~~~~~~~~~~~~~~187 188The attributes for the source and destination are handled separately from adding189an item to a list. This is due to the diverse attributes required for each type190of source and destination. There are functions to create attributes for PCI, VME191and pattern sources and destinations (where appropriate):192 193 - PCI source or destination: :c:func:`vme_dma_pci_attribute`194 - VME source or destination: :c:func:`vme_dma_vme_attribute`195 - Pattern source: :c:func:`vme_dma_pattern_attribute`196 197The function :c:func:`vme_dma_free_attribute` should be used to free an198attribute.199 200 201List Execution202~~~~~~~~~~~~~~203 204The function :c:func:`vme_dma_list_exec` queues a list for execution and will205return once the list has been executed.206 207 208Interrupts209----------210 211The VME API provides functions to attach and detach callbacks to specific VME212level and status ID combinations and for the generation of VME interrupts with213specific VME level and status IDs.214 215 216Attaching Interrupt Handlers217~~~~~~~~~~~~~~~~~~~~~~~~~~~~218 219The function :c:func:`vme_irq_request` can be used to attach and220:c:func:`vme_irq_free` to free a specific VME level and status ID combination.221Any given combination can only be assigned a single callback function. A void222pointer parameter is provided, the value of which is passed to the callback223function, the use of this pointer is user undefined. The callback parameters are224as follows. Care must be taken in writing a callback function, callback225functions run in interrupt context:226 227.. code-block:: c228 229 void callback(int level, int statid, void *priv);230 231 232Interrupt Generation233~~~~~~~~~~~~~~~~~~~~234 235The function :c:func:`vme_irq_generate` can be used to generate a VME interrupt236at a given VME level and VME status ID.237 238 239Location monitors240-----------------241 242The VME API provides the following functionality to configure the location243monitor.244 245 246Location Monitor Management247~~~~~~~~~~~~~~~~~~~~~~~~~~~248 249The function :c:func:`vme_lm_request` is provided to request the use of a block250of location monitors and :c:func:`vme_lm_free` to free them after they are no251longer required. Each block may provide a number of location monitors,252monitoring adjacent locations. The function :c:func:`vme_lm_count` can be used253to determine how many locations are provided.254 255 256Location Monitor Configuration257~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~258 259Once a bank of location monitors has been allocated, the function260:c:func:`vme_lm_set` is provided to configure the location and mode of the261location monitor. The function :c:func:`vme_lm_get` can be used to retrieve262existing settings.263 264 265Location Monitor Use266~~~~~~~~~~~~~~~~~~~~267 268The function :c:func:`vme_lm_attach` enables a callback to be attached and269:c:func:`vme_lm_detach` allows on to be detached from each location monitor270location. Each location monitor can monitor a number of adjacent locations. The271callback function is declared as follows.272 273.. code-block:: c274 275 void callback(void *data);276 277 278Slot Detection279--------------280 281The function :c:func:`vme_slot_num` returns the slot ID of the provided bridge.282 283 284Bus Detection285-------------286 287The function :c:func:`vme_bus_num` returns the bus ID of the provided bridge.288 289 290VME API291-------292 293.. kernel-doc:: drivers/staging/vme_user/vme.h294 :internal:295 296.. kernel-doc:: drivers/staging/vme_user/vme.c297 :export:298