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Diffstat (limited to 'drivers/vme/vme_api.txt')
| -rw-r--r-- | drivers/vme/vme_api.txt | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/drivers/vme/vme_api.txt b/drivers/vme/vme_api.txt new file mode 100644 index 000000000000..856efa35f6e3 --- /dev/null +++ b/drivers/vme/vme_api.txt @@ -0,0 +1,396 @@ + VME Device Driver API + ===================== + +Driver registration +=================== + +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 the following function: + + int vme_register_driver (struct vme_driver *driver); + +If driver registration is successful this function returns zero, if an error +occurred a negative error code will be returned. + +A pointer to a structure of type 'vme_driver' must be provided to the +registration function. The structure is as follows: + + struct vme_driver { + struct list_head node; + const char *name; + int (*match)(struct vme_dev *); + int (*probe)(struct vme_dev *); + int (*remove)(struct vme_dev *); + void (*shutdown)(void); + struct device_driver driver; + struct list_head devices; + unsigned int ndev; + }; + +At the minimum, the '.name', '.match' and '.probe' elements of this structure +should be correctly set. The '.name' element is a pointer to a string holding +the device driver's name. + +The '.match' function allows controlling the number of devices that need to +be registered. The match function should return 1 if a device should be +probed and 0 otherwise. This example match function (from vme_user.c) limits +the number of devices probed to one: + + #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 +probe routine is passed a 'struct vme_dev' pointer as an argument. The +'struct vme_dev' structure looks like the following: + + struct vme_dev { + int num; + struct vme_bridge *bridge; + struct device dev; + struct list_head drv_list; + struct list_head bridge_list; + }; + +Here, the 'num' field refers to the sequential device ID for this specific +driver. The bridge number (or bus number) can be accessed using +dev->bridge->num. + +A function is also provided to unregister the driver from the VME core and is +usually called from the device driver's exit routine: + + void vme_unregister_driver (struct vme_driver *driver); + + +Resource management +=================== + +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 +device structure. This pointer should be saved, it will be required for +requesting VME resources. + +The driver can request ownership of one or more master windows, slave windows +and/or dma channels. Rather than allowing the device driver to request a +specific window or DMA channel (which may be used by a different driver) this +driver allows a resource to be assigned based on the required attributes of the +driver in question: + + struct vme_resource * vme_master_request(struct vme_dev *dev, + u32 aspace, u32 cycle, u32 width); + + struct vme_resource * vme_slave_request(struct vme_dev *dev, u32 aspace, + u32 cycle); + + struct vme_resource *vme_dma_request(struct vme_dev *dev, u32 route); + +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. + +Functions are also provided to free window allocations once they are no longer +required. These functions should be passed the pointer to the resource provided +during resource allocation: + + void vme_master_free(struct vme_resource *res); + + void vme_slave_free(struct vme_resource *res); + + void vme_dma_free(struct vme_resource *res); + + +Master windows +============== + +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 +the underlying chipset. A window must be configured before it can be used. + + +Master window configuration +--------------------------- + +Once a master window has been assigned the following functions can be used to +configure it and retrieve the current settings: + + int vme_master_set (struct vme_resource *res, int enabled, + unsigned long long base, unsigned long long size, u32 aspace, + u32 cycle, u32 width); + + int vme_master_get (struct vme_resource *res, int *enabled, + unsigned long long *base, unsigned long long *size, u32 *aspace, + u32 *cycle, u32 *width); + +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. + +These functions return 0 on success or an error code should the call fail. + + +Master window access +-------------------- + +The following functions can be used to read from and write to configured master +windows. These functions return the number of bytes copied: + + ssize_t vme_master_read(struct vme_resource *res, void *buf, + size_t count, loff_t offset); + + ssize_t vme_master_write(struct vme_resource *res, void *buf, + size_t count, loff_t offset); + +In addition to simple reads and writes, a function is provided to do a +read-modify-write transaction. This function returns the original value of the +VME bus location : + + unsigned int vme_master_rmw (struct vme_resource *res, + unsigned int mask, unsigned int compare, unsigned int swap, + loff_t offset); + +This functions by reading the offset, applying the mask. If the bits selected in +the mask match with the values of the corresponding bits in the compare field, +the value of swap is written the specified offset. + + +Slave windows +============= + +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 +it can be used. + + +Slave window configuration +-------------------------- + +Once a slave window has been assigned the following functions can be used to +configure it and retrieve the current settings: + + int vme_slave_set (struct vme_resource *res, int enabled, + unsigned long long base, unsigned long long size, + dma_addr_t mem, u32 aspace, u32 cycle); + + int vme_slave_get (struct vme_resource *res, int *enabled, + unsigned long long *base, unsigned long long *size, + dma_addr_t *mem, u32 *aspace, u32 *cycle); + +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. + +These functions return 0 on success or an error code should the call fail. + + +Slave window buffer allocation +------------------------------ + +Functions are provided to allow the user to allocate and free a 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 bridge: + + void * vme_alloc_consistent(struct vme_resource *res, size_t size, + dma_addr_t *mem); + + void vme_free_consistent(struct vme_resource *res, size_t size, + void *virt, dma_addr_t mem); + + +Slave window access +------------------- + +Slave windows map local memory onto the VME bus, the standard methods for +accessing memory should be used. + + +DMA channels +============ + +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 +--------------- + +The following functions are provided to create and destroy DMA lists. Execution +of a list will not automatically destroy the list, thus enabling a list to be +reused for repetitive tasks: + + struct vme_dma_list *vme_new_dma_list(struct vme_resource *res); + + int vme_dma_list_free(struct vme_dma_list *list); + + +List Population +--------------- + +An item can be added to a list using the following function ( the source and +destination attributes need to be created before calling this function, this is +covered under "Transfer Attributes"): + + int vme_dma_list_add(struct vme_dma_list *list, + struct vme_dma_attr *src, struct vme_dma_attr *dest, + size_t count); + +NOTE: The detailed attributes of the transfers source and destination + 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. + +Transfer Attributes +------------------- + +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): + +Pattern source: + + struct vme_dma_attr *vme_dma_pattern_attribute(u32 pattern, u32 type); + +PCI source or destination: + + struct vme_dma_attr *vme_dma_pci_attribute(dma_addr_t mem); + +VME source or destination: + + struct vme_dma_attr *vme_dma_vme_attribute(unsigned long long base, + u32 aspace, u32 cycle, u32 width); + +The following function should be used to free an attribute: + + void vme_dma_free_attribute(struct vme_dma_attr *attr); + + +List Execution +-------------- + +The following function queues a list for execution. The function will return +once the list has been executed: + + int vme_dma_list_exec(struct vme_dma_list *list); + + +Interrupts +========== + +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 +---------------------------- + +The following functions can be used to attach and 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: + + int vme_irq_request(struct vme_dev *dev, int level, int statid, + void (*callback)(int, int, void *), void *priv); + + void vme_irq_free(struct vme_dev *dev, int level, int statid); + +The callback parameters are as follows. Care must be taken in writing a callback +function, callback functions run in interrupt context: + + void callback(int level, int statid, void *priv); + + +Interrupt Generation +-------------------- + +The following function can be used to generate a VME interrupt at a given VME +level and VME status ID: + + int vme_irq_generate(struct vme_dev *dev, int level, int statid); + + +Location monitors +================= + +The VME API provides the following functionality to configure the location +monitor. + + +Location Monitor Management +--------------------------- + +The following functions are provided to request the use of a block of location +monitors and to free them after they are no longer required: + + struct vme_resource * vme_lm_request(struct vme_dev *dev); + + void vme_lm_free(struct vme_resource * res); + +Each block may provide a number of location monitors, monitoring adjacent +locations. The following function can be used to determine how many locations +are provided: + + int vme_lm_count(struct vme_resource * res); + + +Location Monitor Configuration +------------------------------ + +Once a bank of location monitors has been allocated, the following functions +are provided to configure the location and mode of the location monitor: + + int vme_lm_set(struct vme_resource *res, unsigned long long base, + u32 aspace, u32 cycle); + + int vme_lm_get(struct vme_resource *res, unsigned long long *base, + u32 *aspace, u32 *cycle); + + +Location Monitor Use +-------------------- + +The following functions allow a callback to be attached and detached from each +location monitor location. Each location monitor can monitor a number of +adjacent locations: + + int vme_lm_attach(struct vme_resource *res, int num, + void (*callback)(int)); + + int vme_lm_detach(struct vme_resource *res, int num); + +The callback function is declared as follows. + + void callback(int num); + + +Slot Detection +============== + +This function returns the slot ID of the provided bridge. + + int vme_slot_get(struct vme_dev *dev); |