| VME Device Drivers |
| ================== |
| |
| 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: |
| |
| .. code-block:: c |
| |
| int vme_register_driver (struct vme_driver *driver, unsigned int ndevs); |
| |
| 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. Along with ndevs, which is the number of devices your |
| driver is able to support. The structure is as follows: |
| |
| .. code-block:: c |
| |
| 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 control over which VME devices should be registered |
| with the driver. 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: |
| |
| .. code-block:: c |
| |
| #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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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 : |
| |
| .. code-block:: c |
| |
| 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. |
| |
| Parts of a VME window can be mapped into user space memory using the following |
| function: |
| |
| .. code-block:: c |
| |
| int vme_master_mmap(struct vme_resource *resource, |
| struct vm_area_struct *vma) |
| |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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"): |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| struct vme_dma_attr *vme_dma_pattern_attribute(u32 pattern, u32 type); |
| |
| PCI source or destination: |
| |
| .. code-block:: c |
| |
| struct vme_dma_attr *vme_dma_pci_attribute(dma_addr_t mem); |
| |
| VME source or destination: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| 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: |
| |
| .. code-block:: c |
| |
| int vme_lm_attach(struct vme_resource *res, int num, |
| void (*callback)(void *)); |
| |
| int vme_lm_detach(struct vme_resource *res, int num); |
| |
| The callback function is declared as follows. |
| |
| .. code-block:: c |
| |
| void callback(void *data); |
| |
| |
| Slot Detection |
| -------------- |
| |
| This function returns the slot ID of the provided bridge. |
| |
| .. code-block:: c |
| |
| int vme_slot_num(struct vme_dev *dev); |
| |
| |
| Bus Detection |
| ------------- |
| |
| This function returns the bus ID of the provided bridge. |
| |
| .. code-block:: c |
| |
| int vme_bus_num(struct vme_dev *dev); |
| |