Tribblix: manual page: devmap.9e

DEVMAP(9E) Driver Entry Points DEVMAP(9E)

NAME

devmap - validate and translate virtual mapping for memory mapped
device

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

int prefixdevmap(dev_t dev, devmap_cookie_t dhp, offset_t off,
size_t len, size_t *maplen, uint_t model);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

dev
Device whose memory is to be mapped.

dhp
An opaque mapping handle that the system uses to describe
the mapping.

off
User offset within the logical device memory at which the
mapping begins.

len
Length (in bytes) of the mapping to be mapped.

maplen
Pointer to length (in bytes) of mapping that has been
validated. maplen is less than or equal to len.

model
The data model type of the current thread.

DESCRIPTION

devmap() is a required entry point for character drivers supporting
memory-mapped devices if the drivers use the devmap framework to set
up the mapping. A memory mapped device has memory that can be mapped
into a process's address space. The mmap(2) system call, when applied
to a character special file, allows this device memory to be mapped
into user space for direct access by the user applications.

As a result of a mmap(2) system call, the system calls the devmap()
entry point during the mapping setup when D_DEVMAP is set in the
cb_flag field of the cb_ops(9S) structure, and any of the following
conditions apply:

o ddi_devmap_segmap(9F) is used as the segmap(9E) entry
point.

o segmap(9E) entry point is set to NULL.

o mmap(9E) entry point is set to NULL.

Otherwise EINVAL will be returned to mmap(2).

Device drivers should use devmap() to validate the user mappings to
the device, to translate the logical offset, off, to the
corresponding physical offset within the device address space, and to
pass the mapping information to the system for setting up the
mapping.

dhp is a device mapping handle that the system uses to describe a
mapping to a memory that is either contiguous in physical address
space or in kernel virtual address space. The system may create
multiple mapping handles in one mmap(2) system call (for example, if
the mapping contains multiple physically discontiguous memory
regions).

model returns the C Language Type Model which the current thread
expects. It is set to DDI_MODEL_ILP32 if the current thread expects
32-bit ( ILP32) semantics, or DDI_MODEL_LP64 if the current thread
expects 64-bit ( LP64) semantics. model is used in combination with
ddi_model_convert_from(9F) to determine whether there is a data model
mismatch between the current thread and the device driver. The device
driver might have to adjust the shape of data structures before
exporting them to a user thread which supports a different data
model.

devmap() should return EINVAL if the logical offset, off, is out of
the range of memory exported by the device to user space. If off +
len exceeds the range of the contiguous memory, devmap() should
return the length from off to the end of the contiguous memory
region. The system will repeatedly call devmap() until the original
mapping length is satisfied. The driver sets *maplen to the validated
length which must be either less than or equal to len.

The devmap() entry point must initialize the mapping parameters
before passing them to the system through either
devmap_devmem_setup(9F) (if the memory being mapped is device memory)
or devmap_umem_setup(9F) (if the memory being mapped is kernel
memory). The devmap() entry point initializes the mapping parameters
by mapping the control callback structure (see
devmap_callback_ctl(9S)), the device access attributes, mapping
length, maximum protection possible for the mapping, and optional
mapping flags. See devmap_devmem_setup(9F) and devmap_umem_setup(9F)
for further information on initializing the mapping parameters.

The system will copy the driver's devmap_callback_ctl(9S) data into
its private memory so the drivers do not need to keep the data
structure after the return from either devmap_devmem_setup(9F) or
devmap_umem_setup(9F).

For device mappings, the system establishes the mapping to the
physical address that corresponds to off by passing the register
number and the offset within the register address space to
devmap_devmem_setup(9F).

For kernel memory mapping, the system selects a user virtual address
that is aligned with the kernel address being mapped for cache
coherence.

RETURN VALUES

0
Successful completion.

Non-zero
An error occurred.

EXAMPLES

Example 1: Implementing the devmap() Entry Point

The following is an example of the implementation for the devmap()
entry point. For mapping device memory, devmap() calls
devmap_devmem_setup(9F) with the register number, rnumber, and the
offset within the register, roff. For mapping kernel memory, the
driver must first allocate the kernel memory using
ddi_umem_alloc(9F). For example, ddi_umem_alloc(9F) can be called in
the attach(9E) routine. The resulting kernel memory cookie is stored
in the driver soft state structure, which is accessible from the
devmap() entry point. See ddi_soft_state(9F). devmap() passes the
cookie obtained from ddi_umem_alloc(9F) and the offset within the
allocated kernel memory to devmap_umem_setup(9F). The corresponding
ddi_umem_free(9F) can be made in the detach(9E) routine to free up
the kernel memory.

...
#define MAPPING_SIZE 0x2000 /* size of the mapping */
#define MAPPING_START 0x70000000 /* logical offset at beginning
of the mapping */
static
struct devmap_callback_ctl xxmap_ops = {
DEVMAP_OPS_REV, /* devmap_ops version number */
xxmap_map, /* devmap_ops map routine */
xxmap_access, /* devmap_ops access routine */
xxmap_dup, /* devmap_ops dup routine */
xxmap_unmap, /* devmap_ops unmap routine */
};

static int
xxdevmap(dev_t dev, devmap_cookie_t dhp, offset_t off, size_t len,
size_t *maplen, uint_t model)
{
int instance;
struct xxstate *xsp;
struct ddi_device_acc_attr *endian_attr;
struct devmap_callback_ctl *callbackops = NULL;
ddi_umem_cookie_t cookie;
dev_info_t *dip;
offset_t roff;
offset_t koff;
uint_t rnumber;
uint_t maxprot;
uint_t flags = 0;
size_t length;
int err;

/* get device soft state */
instance = getminor(dev);
xsp = ddi_get_soft_state(statep, instance);
if (xsp == NULL)
return (-1);

dip = xsp->dip;
/* check for a valid offset */
if ( off is invalid )
return (-1);
/* check if len is within the range of contiguous memory */
if ( (off + len) is contiguous.)
length = len;
else
length = MAPPING_START + MAPPING_SIZE - off;

/* device access attributes */
endian_attr = xsp->endian_attr;

if ( off is referring to a device memory. ) {
/* assign register related parameters */
rnumber = XXX; /* index to register set at off */
roff = XXX; /* offset of rnumber at local bus */
callbackops = &xxmap_ops; /* do all callbacks for this mapping */
maxprot = PROT_ALL; /* allowing all access */
if ((err = devmap_devmem_setup(dhp, dip, callbackops, rnumber, roff,
length, maxprot, flags, endian_attr)) < 0)

return (err);

} else if ( off is referring to a kernel memory.) {
cookie = xsp->cookie; /* cookie is obtained from
ddi_umem_alloc(9F) */
koff = XXX; /* offset within the kernel memory. */
callbackops = NULL; /* don't do callback for this mapping */
maxprot = PROT_ALL; /* allowing all access */
if ((err = devmap_umem_setup(dhp, dip, callbackops, cookie, koff,
length, maxprot, flags, endian_attr)) < 0)
return (err);
}

*maplen = length;
return (0);
}