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>

drivers/staging/vme/TODO

@@ -0,0 +1,388 @@
+			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 follwoing 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;
+		char *name;
+		const struct vme_device_id *bind_table;
+		int (*probe)  (struct device *, int, int);
+		int (*remove) (struct device *, int, int);
+		void (*shutdown) (void);
+		struct device_driver    driver;
+	};
+
+At the minimum, the ???.name???, ???.probe??? and ???.bind_table??? elements of this
+structure should be correctly set. The ???.name??? element is a pointer to a string
+holding the device driver???s name. The ???.probe??? element should contain a pointer
+to the probe routine.
+
+The arguments of the probe routine are as follows:
+
+	probe(struct device *dev, int bus, int slot);
+
+The ???.bind_table??? is a pointer to an array of type ???vme_device_id???:
+
+	struct vme_device_id {
+		int bus;
+		int slot;
+	};
+
+Each structure in this array should provide a bus and slot number where the core
+should probe, using the driver???s probe routine, for a device on the specified
+VME bus.
+
+The VME subsystem supports a single VME driver per ???slot???. There are considered
+to be 32 slots per bus, one for each slot-ID as defined in the ANSI/VITA 1-1994
+specification and are analogious to the physical slots on the VME backplane.
+
+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 probe routine will
+be called for each of the bus/slot combination that becomes valid as VME buses
+are themselves registered.  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 device *dev,
+		vme_address_t aspace, vme_cycle_t cycle, vme_width_t width);
+
+	struct vme_resource * vme_slave_request(struct device *dev,
+		vme_address_t aspace, vme_cycle_t cycle);
+
+TODO:	DMA Resource Allocation incomplete. No attribute based selection.
+
+	struct vme_resource *vme_request_dma(struct device *dev);
+
+For slave windows these attributes are split into those of type ???vme_address_t???
+and ???vme_cycle_t???. Master windows add a further set of attributes ???vme_cycle_t???.
+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. 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 dependant 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,
+		vme_address_t aspace, vme_cycle_t cycle, vme_width_t width);
+
+	int vme_master_get (struct vme_resource *res, int *enabled,
+		unsigned long long *base, unsigned long long *size,
+		vme_address_t *aspace, vme_cycle_t *cycle, vme_width_t *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 broadcast select mask
+-----------------------------------
+
+TODO:	Add functions to set and get Broadcast Select mask:
+
+	int vme_master_bmsk_set (struct vme_resource *res, int mask);
+	int vme_master_bmsk_get (struct vme_resource *res, int *mask);
+
+
+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 dependant 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, vme_address_t aspace, vme_cycle_t cycle);
+
+	int vme_slave_get (struct vme_resource *res, int *enabled,
+		unsigned long long *base, unsigned long long *size,
+		dma_addr_t *mem, vme_address_t *aspace, vme_cycle_t *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);
+
+
+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,
+		vme_pattern_t 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,
+		vme_address_t aspace, vme_cycle_t cycle, vme_width_t 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_request_irq(struct device *dev, int level, int statid,
+		void (*callback)(int, int, void *), void *priv);
+
+	void vme_free_irq(struct device *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_generate_irq(struct device *dev, int level, int statid);
+
+
+Location monitors
+=================
+
+The VME API provides the following functionality to configure the location
+monitor.
+
+
+Location Monitor Management
+---------------------------
+
+TODO:	Provide a mechanism to request use of the location monitor. The location
+	monitors can be moved and we only want one driver to be able to do that
+	at a time! We also need to be able to free the location monitor for
+	others to use.
+
+	struct vme_resource * vme_request_lm(struct device *dev);
+
+	void vme_free_lm(struct vme_resource * res);
+
+
+Location Monitor Configuration
+------------------------------
+
+TODO:	Change to struct "vme_resource *res" rather than "struct device *dev".
+
+The following functions are provided to configure the location and mode of the
+location monitor:
+
+	int vme_lm_set(struct device *dev, unsigned long long base,
+		vme_address_t aspace, vme_cycle_t cycle);
+
+	int vme_lm_get(struct device *dev, unsigned long long *base,
+		vme_address_t *aspace, vme_cycle_t *cycle);
+
+
+Location Monitor Use
+--------------------
+
+TODO:	Change to struct "vme_resource *res" rather than "struct device *dev".
+
+The following functions allow a callback to be attached and detached from each
+location monitor location. The API currently supports 4 location monitors,
+monitoring 4 adjacent locations:
+
+	int vme_lm_attach(struct device *dev, int num,
+		void (*callback)(int));
+
+	int vme_lm_detach(struct device *dev, int num);
+
+The callback function is declared as follows.
+
+	void callback(int num);
+
+
+CR/CSR
+======
+
+TODO:	The VME API needs functions to access the CR/CSR buffer.
+
+Slot Detection
+==============
+
+This function returns the slot ID of the provided bridge.
+
+	int vme_slot_get(struct device *dev);