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Each region has a set of bounds. Within these bounds, allocated segments may reside. Each segment, termed a resource, has several properties which are represented by a 16-bit flag register, as follows.
#define RF_ALLOCATED 0x0001 /* resource has been reserved */ #define RF_ACTIVE 0x0002 /* resource allocation has been activated */ #define RF_SHAREABLE 0x0004 /* resource permits contemporaneous sharing */ #define RF_FIRSTSHARE 0x0020 /* first in sharing list */ #define RF_PREFETCHABLE 0x0040 /* resource is prefetchable */ #define RF_UNMAPPED 0x0100 /* don't map resource when activating */
Bits 15:10 of the flag register are used to represent the desired alignment of the resource within the region.
The rman_init() function initializes the region descriptor, pointed to by the rm argument, for use with the resource management functions. It is required that the fields rm_type and rm_descr of struct rman be set before calling rman_init(). The field rm_type shall be set to RMAN_ARRAY. The field rm_descr shall be set to a string that describes the resource to be managed. The rm_start and rm_end fields may be set to limit the range of acceptable resource addresses. If these fields are not set, rman_init() will initialize them to allow the entire range of resource addresses. It also initializes any mutexes associated with the structure. If rman_init() fails to initialize the mutex, it will return ENOMEM; otherwise it will return 0 and rm will be initialized.
The rman_fini() function frees any structures associated with the structure pointed to by the rm argument. If any of the resources within the managed region have the RF_ALLOCATED flag set, it will return EBUSY; otherwise, any mutexes associated with the structure will be released and destroyed, and the function will return 0.
The rman_manage_region() function establishes the concept of a region which is under rman control. The rman argument points to the region descriptor. The start and end arguments specify the bounds of the region. If successful, rman_manage_region() will return 0. If the region overlaps with an existing region, it will return EBUSY. If any part of the region falls outside of the valid address range for rm, it will return EINVAL. ENOMEM will be returned when rman_manage_region() failed to allocate memory for the region.
The rman_init_from_resource() function is a wrapper routine to create a resource manager backed by an existing resource. It initializes rm using rman_init() and then adds a region to rm corresponding to the address range allocated to r via rman_manage_region().
The rman_first_free_region() and rman_last_free_region() functions can be used to query a resource manager for its first (or last) unallocated region. If rm contains no free region, these functions will return ENOENT. Otherwise, *start and *end are set to the bounds of the free region and zero is returned.
The rman_reserve_resource_bound() function is where the bulk of the rman logic is located. It attempts to reserve a contiguous range in the specified region rm for the use of the device dev. The caller can specify the start and end of an acceptable range, as well as a boundary restriction and required aligment, and the code will attempt to find a free segment which fits. The start argument is the lowest acceptable starting value of the resource. The end argument is the highest acceptable ending value of the resource. Therefore, start, No, +, Fa, count, No, -, 1 must be [<=] end for any allocation to happen. The aligment requirement (if any) is specified in flags. The bound argument may be set to specify a boundary restriction such that an allocated region may cross an address that is a multiple of the boundary. The bound argument must be a power of two. It may be set to zero to specify no boundary restriction. A shared segment will be allocated if the RF_SHAREABLE flag is set, otherwise an exclusive segment will be allocated. If this shared segment already exists, the caller has its device added to the list of consumers.
The rman_reserve_resource() function is used to reserve resources within a previously established region. It is a simplified interface to rman_reserve_resource_bound() which passes 0 for the bound argument.
The rman_make_alignment_flags() function returns the flag mask corresponding to the desired alignment size. This should be used when calling rman_reserve_resource_bound().
The rman_is_region_manager() function returns true if the allocated resource r was allocated from rm. Otherwise, it returns false.
The rman_adjust_resource() function is used to adjust the reserved address range of an allocated resource to reserve start through end. It can be used to grow or shrink one or both ends of the resource range. The current implementation does not support entirely relocating the resource and will fail with EINVAL if the new resource range does not overlap the old resource range. If either end of the resource range grows and the new resource range would conflict with another allocated resource, the function will fail with EBUSY. The rman_adjust_resource() function does not support adjusting the resource range for shared resources and will fail such attempts with EINVAL. Upon success, the resource r will have a start address of start and an end address of end and the function will return zero. Note that none of the constraints of the original allocation request such as alignment or boundary restrictions are checked by rman_adjust_resource(). It is the caller's responsibility to enforce any such requirements.
The rman_release_resource() function releases the reserved resource r. It may attempt to merge adjacent free resources.
The rman_activate_resource() function marks a resource as active, by setting the RF_ACTIVE flag. If this is a time shared resource, and the caller has not yet acquired the resource, the function returns EBUSY.
The rman_deactivate_resource() function marks a resource r as inactive, by clearing the RF_ACTIVE flag. If other consumers are waiting for this range, it will wakeup their threads.
The rman_get_start(), rman_get_end(), rman_get_size(), and rman_get_flags() functions return the bounds, size and flags of the previously reserved resource r.
The rman_set_bustag() function associates a bus_space_tag_t t with the resource r. The rman_get_bustag() function is used to retrieve this tag once set.
The rman_set_bushandle() function associates a bus_space_handle_t h with the resource r. The rman_get_bushandle() function is used to retrieve this handle once set.
The rman_set_virtual() function is used to associate a kernel virtual address with a resource r. The rman_get_virtual() function can be used to retrieve the KVA once set.
The rman_set_mapping() function is used to associate a resource mapping with a resource r. The mapping must cover the entire resource. Setting a mapping sets the associated bus_space(9) handle and tag for r as well as the kernel virtual address if the mapping contains one. These individual values can be retrieved via rman_get_bushandle(), rman_get_bustag(), and rman_get_virtual().
The rman_get_mapping() function can be used to retrieve the associated resource mapping once set.
The rman_set_rid() function associates a resource identifier with a resource r. The rman_get_rid() function retrieves this RID.
The rman_get_device() function returns a pointer to the device which reserved the resource r.
|RMAN (9)||May 20, 2016|
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|“||Like a classics radio station whose play list spans decades, Unix simultaneously exhibits its mixed and dated heritage. There's Clash-era graphics interfaces; Beatles-era two-letter command names; and systems programs (for example, ps) whose terse and obscure output was designed for slow teletypes; Bing Crosby-era command editing (# and @ are still the default line editing commands), and Scott Joplin-era core dumps.||”|
|— The Unix Haters' handbook|