Staging: vme: add TODO file
This describes the current vme api, along with a list of things that needs to be fixed up. Signed-off-by: Martyn Welch <martyn.welch@gefanuc.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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Martyn Welch
Greg Kroah-Hartman
parent
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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 follwoing 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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char *name;
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const struct vme_device_id *bind_table;
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int (*probe) (struct device *, int, int);
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int (*remove) (struct device *, int, int);
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void (*shutdown) (void);
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struct device_driver driver;
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};
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At the minimum, the ???.name???, ???.probe??? and ???.bind_table??? elements of this
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structure should be correctly set. The ???.name??? element is a pointer to a string
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holding the device driver???s name. The ???.probe??? element should contain a pointer
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to the probe routine.
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The arguments of the probe routine are as follows:
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probe(struct device *dev, int bus, int slot);
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The ???.bind_table??? is a pointer to an array of type ???vme_device_id???:
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struct vme_device_id {
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int bus;
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int slot;
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};
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Each structure in this array should provide a bus and slot number where the core
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should probe, using the driver???s probe routine, for a device on the specified
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VME bus.
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The VME subsystem supports a single VME driver per ???slot???. There are considered
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to be 32 slots per bus, one for each slot-ID as defined in the ANSI/VITA 1-1994
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specification and are analogious to the physical slots on the VME backplane.
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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 probe routine will
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be called for each of the bus/slot combination that becomes valid as VME buses
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are themselves registered. 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 device *dev,
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vme_address_t aspace, vme_cycle_t cycle, vme_width_t width);
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struct vme_resource * vme_slave_request(struct device *dev,
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vme_address_t aspace, vme_cycle_t cycle);
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TODO: DMA Resource Allocation incomplete. No attribute based selection.
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struct vme_resource *vme_request_dma(struct device *dev);
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For slave windows these attributes are split into those of type ???vme_address_t???
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and ???vme_cycle_t???. Master windows add a further set of attributes ???vme_cycle_t???.
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These attributes are defined as bitmasks and as such any combination of the
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attributes can be requested for a single window, the core will assign a window
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that meets the requirements, returning a pointer of type vme_resource that
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should be used to identify the allocated resource when it is used. If an
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unallocated window fitting the requirements can not be found a NULL pointer will
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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 dependant 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,
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vme_address_t aspace, vme_cycle_t cycle, vme_width_t 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,
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vme_address_t *aspace, vme_cycle_t *cycle, vme_width_t *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 broadcast select mask
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-----------------------------------
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TODO: Add functions to set and get Broadcast Select mask:
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int vme_master_bmsk_set (struct vme_resource *res, int mask);
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int vme_master_bmsk_get (struct vme_resource *res, int *mask);
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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 dependant 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, vme_address_t aspace, vme_cycle_t 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, vme_address_t *aspace, vme_cycle_t *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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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,
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vme_pattern_t 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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vme_address_t aspace, vme_cycle_t cycle, vme_width_t 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_request_irq(struct device *dev, int level, int statid,
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void (*callback)(int, int, void *), void *priv);
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void vme_free_irq(struct device *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_generate_irq(struct device *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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TODO: Provide a mechanism to request use of the location monitor. The location
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monitors can be moved and we only want one driver to be able to do that
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at a time! We also need to be able to free the location monitor for
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others to use.
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struct vme_resource * vme_request_lm(struct device *dev);
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void vme_free_lm(struct vme_resource * res);
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Location Monitor Configuration
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------------------------------
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TODO: Change to struct "vme_resource *res" rather than "struct device *dev".
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The following functions are provided to configure the location and mode of the
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location monitor:
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int vme_lm_set(struct device *dev, unsigned long long base,
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vme_address_t aspace, vme_cycle_t cycle);
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int vme_lm_get(struct device *dev, unsigned long long *base,
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vme_address_t *aspace, vme_cycle_t *cycle);
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Location Monitor Use
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--------------------
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TODO: Change to struct "vme_resource *res" rather than "struct device *dev".
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The following functions allow a callback to be attached and detached from each
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location monitor location. The API currently supports 4 location monitors,
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monitoring 4 adjacent locations:
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int vme_lm_attach(struct device *dev, int num,
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void (*callback)(int));
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int vme_lm_detach(struct device *dev, 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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CR/CSR
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======
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TODO: The VME API needs functions to access the CR/CSR buffer.
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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 device *dev);
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