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rsrcdbmgr_attach()

Reserve a system resource for a process

Synopsis:

#include <sys/rsrcdbmgr.h>
#include <sys/rsrcdbmsg.h>

int rsrcdbmgr_attach( rsrc_request_t * list,
                      int count );

Arguments:

list

An array of rsrc_request_t structures that describe the resources that you want to reserve; see below.

count

The number of entries in the array.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The resource database manager allocates and keeps track of system resources i.e. it manages these resources. The system resources currently tracked are:

• memory
• IRQs
• DMA channels
• I/O ports.

Major and minor device numbers are handled with separate rsrcdbmgr_devno_attach() and rsrcdbmgr_devno_detach() functions.

There are two main functions that drivers can use to communicate with the resource database:

• rsrcdbmgr_attach()
• rsrcdbmgr_detach()

The rsrcdbmgr_attach() function reserves a resource range(s) from the database of available resources for a process. Other processes can't reserve this resource range until the resource is returned to the system (usually with the rsrcdbmgr_detach() call). The requested resources are returned in a list of _rsrc_request structures with the start and end fields filled in. The number of resources requested is specified in count.

Reserving the resources doesn't give you access to them; you still have to use mmap(), InterruptAttach(), or another means.

When you're finished with the resource, you must return it to the system. The easiest way to return the resource is to call rsrcdbmgr_detach() with the same start, end, and type (via the flags field) that were issued for the resource.

rsrc_request_t structure

The resource requests structure looks like this:

typedef struct _rsrc_request {
   uint64_t   length;
   uint64_t   align;
   uint64_t   start;
   uint64_t   end;
   uint32_t   flags;
   uint32_t   zero[3];   /* Reserved */
} rsrc_request_t;

The members include:

length

The length of the resource that you want to reserve. You must set this member.

align

The alignment of the resource.

start, end

The range of resource that you want to reserve.

flags

The type of the resource, as well as flags that affect the request. You must set this member to be one of the following resource types (defined in <sys/rsrcdbmgr.h>):

• RSRCDBMGR_DMA_CHANNEL -- DMA channel
• RSRCDBMGR_IO_PORT -- I/O port address
• RSRCDBMGR_IRQ -- Interrupt address
• RSRCDBMGR_MEMORY -- Memory address
• RSRCDBMGR_PCI_MEMORY -- PCI memory address

You can OR in the following flags (also defined in <sys/rsrcdbmgr.h>):

• RSRCDBMGR_FLAG_ALIGN -- the contents of the align field are valid, and the requested resource starts with the given alignment.
• RSRCDBMGR_FLAG_RANGE -- the contents of the start and end fields are valid, and the requested resource is in the range start to end, inclusive.
• RSRCDBMGR_FLAG_SHARE -- other processes can have access to an allocated resource.
• RSRCDBMGR_FLAG_TOPDOWN -- start the search for a free resource block from end. If you also set RSRCDBMGR_FLAG_RANGE, this flag makes the search start from the end of the available range.

Returns:

EOK, or -1 if an error occurred (errno is set).

Errors:

EAGAIN

The resource request can't be filled.

EINVAL

Invalid argument.

ENOMEM

Insufficient memory to allocate internal data structures.

Examples:

When you start the system, the startup code and special programs that know how to probe the hardware call rsrcdbmgr_create() to register the hardware in the resource database. The following examples don't do this seeding, so they'll fail with an error code of EINVAL.

Example 1

/* 
 * Request one DMA Channel, with length 1, from the
 * entire range of available DMA channel resources.
 */
#include <stdio.h>
#include <sys/rsrcdbmgr.h>
#include <sys/rsrcdbmsg.h>

int main(int argc, char **argv) {
    int count;
    rsrc_request_t req;

    memset(&req, 0, sizeof(req));
    req.length = 1;
    req.flags = RSRCDBMGR_DMA_CHANNEL;
    count = 1;

    if (rsrcdbmgr_attach( &req, count) == -1) {
        perror("Problem attaching to resource ");
        exit(1);
    }

    printf("You can use DMA channel 0x%llx \n", 
            req.start);

    ...
    /* Do something with the acquired resource */
    ...

    /* To return the resource to the database: */
    if (rsrcdbmgr_detach( &req, count) == -1) {
        perror("Problem detaching resource \n");
        exit(1);
    }

    return(0);
}

Example 2

/* 
 * Request memory that's 4-byte aligned
 * and has a length of 50.
 */

#include <stdio.h>
#include <sys/rsrcdbmgr.h>
#include <sys/rsrcdbmsg.h>

int main(int argc, char **argv) {
    int count;
    rsrc_request_t req;

    memset(&req, 0, sizeof(req));
    req.align = 4;
    req.length = 50;
    req.flags = RSRCDBMGR_FLAG_ALIGN | RSRCDBMGR_MEMORY;
    count = 1;

    if (rsrcdbmgr_attach(&req, count) == -1) {
        perror("Problem attaching to resource ");
        exit(1);
    }

    printf("You can use memory from 0x%llx 0x%llx inclusive. \n", 
            req.start, req.end );

    ...
    /* Do something with the acquired resource */
    ...

    /* To return the resource to the database: */
    if (rsrcdbmgr_detach( &req, count) == -1) {
        perror("Problem detaching resource \n");
        exit(1);
    }

    return(0);
}

Example 3

 
/* 
 * Request two resources:
 * I/O port 0 and an IRQ in the range 10-12
 * from the available resources.
 */
#include <stdio.h>
#include <sys/rsrcdbmgr.h>
#include <sys/rsrcdbmsg.h>

int main(int argc, char **argv) {
    int count;
    rsrc_request_t req[2];

    memset(req, 0, 2*sizeof(*req));
    req[0].start = 0;
    req[0].end = 0;
    req[0].length = 1; 
    req[0].flags = RSRCDBMGR_FLAG_RANGE | RSRCDBMGR_IO_PORT;

    req[1].start = 10;
    req[1].end = 12;
    req[1].length = 1; 
    req[1].flags = RSRCDBMGR_FLAG_RANGE | RSRCDBMGR_IRQ;
    count = 2;

    if (rsrcdbmgr_attach(req, count) == -1) {
        perror("Problem attaching to resource ");
        exit(1);
    }

    printf("You can use io-port 0x%llx \n",
            req[0].start);
    printf("You can use irq 0x%llx \n", 
            req[1].start);

    ...
    /* Do something with the acquired resource */
    ...

    /* To return the resource to the database: */
    if (rsrcdbmgr_detach(req, count) == -1) {
        perror("Problem detaching resource \n");
        exit(1);
    }

    return(0);
}

Classification:

QNX Neutrino

See also:

rsrcdbmgr_create(), rsrcdbmgr_detach(), rsrcdbmgr_destroy(), rsrcdbmgr_devno_attach(), rsrcdbmgr_devno_detach(), rsrcdbmgr_query()