1segmap(9E) Driver Entry Points segmap(9E)
2
6 segmap - map device memory into user space
7
9 #include <sys/types.h>
10 #include <sys/mman.h>
11 #include <sys/param.h>
12 #include <sys/vm.h>
13 #include <sys/ddi.h>
14 #include <sys/sunddi.h>
15 int prefixsegmap(dev_t dev, off_t off, struct as *asp, caddr_t *addrp,
19 off_t len, unsigned int prot, unsigned int maxprot, unsigned int flags,
20 cred_t *cred_p);
21
24 Architecture independent level 2 (DKI only).
25
27 dev Device whose memory is to be mapped.
28 off Offset within device memory at which mapping begins.
31 asp Pointer to the address space into which the device memory
34 should be mapped.
35 addrp Pointer to the address in the address space to which the
38 device memory should be mapped.
39 len Length (in bytes) of the memory to be mapped.
42 prot A bit field that specifies the protections. Possible set‐
45 tings are:
46 PROT_READ Read access is desired.
48 PROT_WRITE Write access is desired.
51 PROT_EXEC Execute access is desired.
54 PROT_USER User-level access is desired (the mapping is
57 being done as a result of a mmap(2) system
58 call).
59 PROT_ALL All access is desired.
62 maxprot Maximum protection flag possible for attempted mapping; the
66 PROT_WRITE bit may be masked out if the user opened the
67 special file read-only.
68 flags Flags indicating type of mapping. Possible values are
71 (other bits may be set):
72 MAP_SHARED Changes should be shared.
74 MAP_PRIVATE Changes are private.
77 cred_p Pointer to the user credentials structure.
81
84 The segmap() entry point is an optional routine for character drivers
85 that support memory mapping. The mmap(2) system call, when applied to
86 a character special file, allows device memory to be mapped into user
87 space for direct access by the user application.
88 Typically, a character driver that needs to support the mmap(2) system
91 call supplies either an devmap(9E) entry point, or both an devmap(9E)
92 and a segmap() entry point routine (see the devmap(9E) reference
93 page). If no segmap() entry point is provided for the driver,
94 devmap_setup(9F) is used as a default.
95 A driver for a memory-mapped device would provide a segmap() entry
98 point if it:
99 o needs to maintain a separate context for each user mapping.
101 See devmap_setup(9F) for details.
102 o needs to assign device access attributes to the user map‐
104 ping.
105 The responsibilities of a segmap() entry point are:
108 o Verify that the range, defined by offset and len, to be
110 mapped is valid for the device. Typically, this task is
111 performed by calling the devmap(9E) entry point. Note that
112 if you are using ddi_devmap_segmap(9F) or devmap_setup(9F)
113 to set up the mapping, it will call your devmap(9E) entry
114 point for you to validate the range to be mapped.
115 o Assign device access attributes to the mapping. See
117 ddi_devmap_segmap(9F), and ddi_device_acc_attr(9S) for
118 details.
119 o Set up device contexts for the user mapping if your device
121 requires context switching. See devmap_setup(9F) for
122 details.
123 o Perform the mapping with ddi_devmap_segmap(9F), or
125 devmap_setup(9F) and return the status if it fails.
126
128 The segmap() routine should return 0 if the driver is successful in
129 performing the memory map of its device address space into the speci‐
130 fied address space.
131 The segmap() must return an error number on failure. For example, valid
134 error numbers would be ENXIO if the offset/length pair specified
135 exceeds the limits of the device memory, or EINVAL if the driver
136 detects an invalid type of mapping attempted.
137 If one of the mapping routines ddi_devmap_segmap() or devmap_set‐
140 up()fails, you must return the error number returned by the respective
141 routine.
142
144 mmap(2), devmap(9E), devmap_setup(9F), ddi_devmap_segmap(9F),
145 ddi_device_acc_attr(9S)
146 Writing Device Drivers
149SunOS 5.11 14 Jan 1997 segmap(9E)