MMIO wrapper functions for the Linux userspace /dev/mem device.
#include <periphery/mmio.h>
/* Primary Functions */
int mmio_open(mmio_t *mmio, uintptr_t base, size_t size);
void *mmio_ptr(mmio_t *mmio);
int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value);
int mmio_read16(mmio_t *mmio, uintptr_t offset, uint16_t *value);
int mmio_read8(mmio_t *mmio, uintptr_t offset, uint8_t *value);
int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len);
int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value);
int mmio_write16(mmio_t *mmio, uintptr_t offset, uint16_t value);
int mmio_write8(mmio_t *mmio, uintptr_t offset, uint8_t value);
int mmio_write(mmio_t *mmio, uintptr_t offset, const uint8_t *buf, size_t len);
int mmio_close(mmio_t *mmio);
/* Miscellaneous */
uintptr_t mmio_base(mmio_t *mmio);
size_t mmio_size(mmio_t *mmio);
int mmio_tostring(mmio_t *mmio, char *str, size_t len);
/* Error Handling */
int mmio_errno(mmio_t *mmio);
const char *mmio_errmsg(mmio_t *mmio);int mmio_open(mmio_t *mmio, uintptr_t base, size_t size);Map the region of physical memory at the specified base address with the specified size.
mmio should be a valid pointer to an allocated MMIO handle structure. Neither base nor size need be aligned to a page boundary.
Returns 0 on success, or a negative MMIO error code on failure.
void *mmio_ptr(mmio_t *mmio);Return the pointer to the mapped physical memory.
This function is a simple accessor to the MMIO handle structure and always succeeds.
int mmio_read32(mmio_t *mmio, uintptr_t offset, uint32_t *value);
int mmio_read16(mmio_t *mmio, uintptr_t offset, uint16_t *value);
int mmio_read8(mmio_t *mmio, uintptr_t offset, uint8_t *value);
int mmio_read(mmio_t *mmio, uintptr_t offset, uint8_t *buf, size_t len);Read 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, from mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
Returns 0 on success, or a negative MMIO error code on failure.
int mmio_write32(mmio_t *mmio, uintptr_t offset, uint32_t value);
int mmio_write16(mmio_t *mmio, uintptr_t offset, uint16_t value);
int mmio_write8(mmio_t *mmio, uintptr_t offset, uint8_t value);
int mmio_write(mmio_t *mmio, uintptr_t offset, const uint8_t *buf, size_t len);Write 32-bits, 16-bits, 8-bits, or an array of bytes, respectively, to mapped physical memory, starting at the specified byte offset, relative to the base address the MMIO handle was opened with.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
Returns 0 on success, or a negative MMIO error code on failure.
int mmio_close(mmio_t *mmio);Unmap mapped physical memory.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
Returns 0 on success, or a negative MMIO error code on failure.
uintptr_t mmio_base(mmio_t *mmio);Return the base address the MMIO handle was opened with.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
This function is a simple accessor to the MMIO handle structure and always succeeds.
size_t mmio_size(mmio_t *mmio);Return the size the MMIO handle was opened with.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
This function is a simple accessor to the MMIO handle structure and always succeeds.
int mmio_tostring(mmio_t *mmio, char *str, size_t len);Return a string representation of the MMIO handle.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
This function behaves and returns like snprintf().
int mmio_errno(mmio_t *mmio);Return the libc errno of the last failure that occurred.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
const char *mmio_errmsg(mmio_t *mmio);Return a human readable error message of the last failure that occurred.
mmio should be a valid pointer to an MMIO handle opened with mmio_open().
The periphery MMIO functions return 0 on success or one of the negative error codes below on failure.
The libc errno of the failure in an underlying libc library call can be obtained with the mmio_errno() helper function. A human readable error message can be obtained with the mmio_errmsg() helper function.
| Error Code | Description |
|---|---|
MMIO_ERROR_ARG |
Invalid arguments |
MMIO_ERROR_OPEN |
Opening /dev/mem |
MMIO_ERROR_MAP |
Mapping memory |
MMIO_ERROR_CLOSE |
Closing /dev/mem |
MMIO_ERROR_UNMAP |
Unmapping memory |
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "mmio.h"
struct am335x_rtcss_registers {
uint32_t seconds; /* 0x00 */
uint32_t minutes; /* 0x04 */
uint32_t hours; /* 0x08 */
/* ... */
};
int main(void) {
mmio_t mmio;
uint32_t mac_id0_lo, mac_id0_hi;
volatile struct am335x_rtcss_registers *regs;
/* Open control module */
if (mmio_open(&mmio, 0x44E10000, 0x1000) < 0) {
fprintf(stderr, "mmio_open(): %s\n", mmio_errmsg(&mmio));
exit(1);
}
/* Read lower 2 bytes of MAC address */
if (mmio_read32(&mmio, 0x630, &mac_id0_lo) < 0) {
fprintf(stderr, "mmio_read32(): %s\n", mmio_errmsg(&mmio));
exit(1);
}
/* Read upper 4 bytes of MAC address */
if (mmio_read32(&mmio, 0x634, &mac_id0_hi) < 0) {
fprintf(stderr, "mmio_read32(): %s\n", mmio_errmsg(&mmio));
exit(1);
}
printf("MAC address: %04x%08x\n", mac_id0_lo, mac_id0_hi);
mmio_close(&mmio);
/* Open RTC subsystem */
if (mmio_open(&mmio, 0x44E3E000, 0x1000) < 0) {
fprintf(stderr, "mmio_open(): %s\n", mmio_errmsg(&mmio));
exit(1);
}
regs = mmio_ptr(&mmio);
/* Read current RTC time */
printf("hours: %02x minutes: %02x seconds %02x\n", regs->hours, regs->minutes, regs->seconds);
mmio_close(&mmio);
return 0;
}