397 lines
13 KiB
Plaintext
397 lines
13 KiB
Plaintext
VME Device Driver API
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=====================
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Driver registration
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===================
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As with other subsystems within the Linux kernel, VME device drivers register
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with the VME subsystem, typically called from the devices init routine. This is
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achieved via a call to the following function:
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int vme_register_driver (struct vme_driver *driver);
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If driver registration is successful this function returns zero, if an error
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occurred a negative error code will be returned.
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A pointer to a structure of type 'vme_driver' must be provided to the
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registration function. The structure is as follows:
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struct vme_driver {
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struct list_head node;
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const char *name;
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int (*match)(struct vme_dev *);
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int (*probe)(struct vme_dev *);
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int (*remove)(struct vme_dev *);
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void (*shutdown)(void);
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struct device_driver driver;
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struct list_head devices;
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unsigned int ndev;
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};
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At the minimum, the '.name', '.match' and '.probe' elements of this structure
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should be correctly set. The '.name' element is a pointer to a string holding
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the device driver's name.
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The '.match' function allows controlling the number of devices that need to
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be registered. The match function should return 1 if a device should be
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probed and 0 otherwise. This example match function (from vme_user.c) limits
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the number of devices probed to one:
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#define USER_BUS_MAX 1
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...
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static int vme_user_match(struct vme_dev *vdev)
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{
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if (vdev->id.num >= USER_BUS_MAX)
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return 0;
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return 1;
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}
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The '.probe' element should contain a pointer to the probe routine. The
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probe routine is passed a 'struct vme_dev' pointer as an argument. The
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'struct vme_dev' structure looks like the following:
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struct vme_dev {
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int num;
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struct vme_bridge *bridge;
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struct device dev;
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struct list_head drv_list;
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struct list_head bridge_list;
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};
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Here, the 'num' field refers to the sequential device ID for this specific
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driver. The bridge number (or bus number) can be accessed using
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dev->bridge->num.
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A function is also provided to unregister the driver from the VME core and is
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usually called from the device driver's exit routine:
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void vme_unregister_driver (struct vme_driver *driver);
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Resource management
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===================
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Once a driver has registered with the VME core the provided match routine will
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be called the number of times specified during the registration. If a match
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succeeds, a non-zero value should be returned. A zero return value indicates
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failure. For all successful matches, the probe routine of the corresponding
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driver is called. The probe routine is passed a pointer to the devices
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device structure. This pointer should be saved, it will be required for
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requesting VME resources.
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The driver can request ownership of one or more master windows, slave windows
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and/or dma channels. Rather than allowing the device driver to request a
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specific window or DMA channel (which may be used by a different driver) this
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driver allows a resource to be assigned based on the required attributes of the
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driver in question:
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struct vme_resource * vme_master_request(struct vme_dev *dev,
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u32 aspace, u32 cycle, u32 width);
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struct vme_resource * vme_slave_request(struct vme_dev *dev, u32 aspace,
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u32 cycle);
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struct vme_resource *vme_dma_request(struct vme_dev *dev, u32 route);
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For slave windows these attributes are split into the VME address spaces that
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need to be accessed in 'aspace' and VME bus cycle types required in 'cycle'.
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Master windows add a further set of attributes in 'width' specifying the
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required data transfer widths. These attributes are defined as bitmasks and as
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such any combination of the attributes can be requested for a single window,
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the core will assign a window that meets the requirements, returning a pointer
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of type vme_resource that should be used to identify the allocated resource
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when it is used. For DMA controllers, the request function requires the
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potential direction of any transfers to be provided in the route attributes.
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This is typically VME-to-MEM and/or MEM-to-VME, though some hardware can
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support VME-to-VME and MEM-to-MEM transfers as well as test pattern generation.
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If an unallocated window fitting the requirements can not be found a NULL
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pointer will be returned.
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Functions are also provided to free window allocations once they are no longer
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required. These functions should be passed the pointer to the resource provided
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during resource allocation:
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void vme_master_free(struct vme_resource *res);
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void vme_slave_free(struct vme_resource *res);
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void vme_dma_free(struct vme_resource *res);
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Master windows
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==============
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Master windows provide access from the local processor[s] out onto the VME bus.
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The number of windows available and the available access modes is dependent on
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the underlying chipset. A window must be configured before it can be used.
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Master window configuration
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---------------------------
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Once a master window has been assigned the following functions can be used to
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configure it and retrieve the current settings:
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int vme_master_set (struct vme_resource *res, int enabled,
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unsigned long long base, unsigned long long size, u32 aspace,
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u32 cycle, u32 width);
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int vme_master_get (struct vme_resource *res, int *enabled,
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unsigned long long *base, unsigned long long *size, u32 *aspace,
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u32 *cycle, u32 *width);
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The address spaces, transfer widths and cycle types are the same as described
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under resource management, however some of the options are mutually exclusive.
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For example, only one address space may be specified.
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These functions return 0 on success or an error code should the call fail.
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Master window access
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--------------------
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The following functions can be used to read from and write to configured master
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windows. These functions return the number of bytes copied:
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ssize_t vme_master_read(struct vme_resource *res, void *buf,
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size_t count, loff_t offset);
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ssize_t vme_master_write(struct vme_resource *res, void *buf,
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size_t count, loff_t offset);
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In addition to simple reads and writes, a function is provided to do a
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read-modify-write transaction. This function returns the original value of the
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VME bus location :
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unsigned int vme_master_rmw (struct vme_resource *res,
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unsigned int mask, unsigned int compare, unsigned int swap,
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loff_t offset);
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This functions by reading the offset, applying the mask. If the bits selected in
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the mask match with the values of the corresponding bits in the compare field,
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the value of swap is written the specified offset.
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Slave windows
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=============
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Slave windows provide devices on the VME bus access into mapped portions of the
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local memory. The number of windows available and the access modes that can be
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used is dependent on the underlying chipset. A window must be configured before
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it can be used.
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Slave window configuration
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--------------------------
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Once a slave window has been assigned the following functions can be used to
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configure it and retrieve the current settings:
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int vme_slave_set (struct vme_resource *res, int enabled,
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unsigned long long base, unsigned long long size,
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dma_addr_t mem, u32 aspace, u32 cycle);
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int vme_slave_get (struct vme_resource *res, int *enabled,
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unsigned long long *base, unsigned long long *size,
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dma_addr_t *mem, u32 *aspace, u32 *cycle);
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The address spaces, transfer widths and cycle types are the same as described
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under resource management, however some of the options are mutually exclusive.
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For example, only one address space may be specified.
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These functions return 0 on success or an error code should the call fail.
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Slave window buffer allocation
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------------------------------
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Functions are provided to allow the user to allocate and free a contiguous
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buffers which will be accessible by the VME bridge. These functions do not have
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to be used, other methods can be used to allocate a buffer, though care must be
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taken to ensure that they are contiguous and accessible by the VME bridge:
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void * vme_alloc_consistent(struct vme_resource *res, size_t size,
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dma_addr_t *mem);
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void vme_free_consistent(struct vme_resource *res, size_t size,
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void *virt, dma_addr_t mem);
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Slave window access
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-------------------
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Slave windows map local memory onto the VME bus, the standard methods for
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accessing memory should be used.
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DMA channels
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============
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The VME DMA transfer provides the ability to run link-list DMA transfers. The
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API introduces the concept of DMA lists. Each DMA list is a link-list which can
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be passed to a DMA controller. Multiple lists can be created, extended,
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executed, reused and destroyed.
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List Management
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---------------
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The following functions are provided to create and destroy DMA lists. Execution
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of a list will not automatically destroy the list, thus enabling a list to be
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reused for repetitive tasks:
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struct vme_dma_list *vme_new_dma_list(struct vme_resource *res);
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int vme_dma_list_free(struct vme_dma_list *list);
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List Population
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---------------
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An item can be added to a list using the following function ( the source and
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destination attributes need to be created before calling this function, this is
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covered under "Transfer Attributes"):
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int vme_dma_list_add(struct vme_dma_list *list,
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struct vme_dma_attr *src, struct vme_dma_attr *dest,
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size_t count);
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NOTE: The detailed attributes of the transfers source and destination
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are not checked until an entry is added to a DMA list, the request
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for a DMA channel purely checks the directions in which the
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controller is expected to transfer data. As a result it is
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possible for this call to return an error, for example if the
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source or destination is in an unsupported VME address space.
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Transfer Attributes
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-------------------
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The attributes for the source and destination are handled separately from adding
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an item to a list. This is due to the diverse attributes required for each type
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of source and destination. There are functions to create attributes for PCI, VME
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and pattern sources and destinations (where appropriate):
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Pattern source:
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struct vme_dma_attr *vme_dma_pattern_attribute(u32 pattern, u32 type);
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PCI source or destination:
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struct vme_dma_attr *vme_dma_pci_attribute(dma_addr_t mem);
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VME source or destination:
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struct vme_dma_attr *vme_dma_vme_attribute(unsigned long long base,
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u32 aspace, u32 cycle, u32 width);
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The following function should be used to free an attribute:
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void vme_dma_free_attribute(struct vme_dma_attr *attr);
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List Execution
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--------------
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The following function queues a list for execution. The function will return
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once the list has been executed:
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int vme_dma_list_exec(struct vme_dma_list *list);
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Interrupts
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==========
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The VME API provides functions to attach and detach callbacks to specific VME
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level and status ID combinations and for the generation of VME interrupts with
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specific VME level and status IDs.
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Attaching Interrupt Handlers
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----------------------------
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The following functions can be used to attach and free a specific VME level and
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status ID combination. Any given combination can only be assigned a single
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callback function. A void pointer parameter is provided, the value of which is
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passed to the callback function, the use of this pointer is user undefined:
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int vme_irq_request(struct vme_dev *dev, int level, int statid,
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void (*callback)(int, int, void *), void *priv);
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void vme_irq_free(struct vme_dev *dev, int level, int statid);
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The callback parameters are as follows. Care must be taken in writing a callback
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function, callback functions run in interrupt context:
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void callback(int level, int statid, void *priv);
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Interrupt Generation
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--------------------
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The following function can be used to generate a VME interrupt at a given VME
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level and VME status ID:
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int vme_irq_generate(struct vme_dev *dev, int level, int statid);
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Location monitors
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=================
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The VME API provides the following functionality to configure the location
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monitor.
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Location Monitor Management
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---------------------------
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The following functions are provided to request the use of a block of location
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monitors and to free them after they are no longer required:
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struct vme_resource * vme_lm_request(struct vme_dev *dev);
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void vme_lm_free(struct vme_resource * res);
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Each block may provide a number of location monitors, monitoring adjacent
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locations. The following function can be used to determine how many locations
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are provided:
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int vme_lm_count(struct vme_resource * res);
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Location Monitor Configuration
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------------------------------
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Once a bank of location monitors has been allocated, the following functions
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are provided to configure the location and mode of the location monitor:
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int vme_lm_set(struct vme_resource *res, unsigned long long base,
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u32 aspace, u32 cycle);
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int vme_lm_get(struct vme_resource *res, unsigned long long *base,
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u32 *aspace, u32 *cycle);
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Location Monitor Use
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--------------------
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The following functions allow a callback to be attached and detached from each
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location monitor location. Each location monitor can monitor a number of
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adjacent locations:
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int vme_lm_attach(struct vme_resource *res, int num,
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void (*callback)(int));
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int vme_lm_detach(struct vme_resource *res, int num);
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The callback function is declared as follows.
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void callback(int num);
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Slot Detection
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==============
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This function returns the slot ID of the provided bridge.
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int vme_slot_get(struct vme_dev *dev);
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