#include "mbox.h" // See at https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface // For messsage description // E.g. for Get firmware revision // // Tag: 0x00000001 // Request: // Length: 0 // Response: // Length: 4 // Value: // u32: firmware revision // mbox[0] = 4 * 6 // total length in byte // mbox[1] = MBOX_REQUEST // mbox[2] = 0x00000001 // mbox[3] = max(req_length, resp_length) -> 4 // mbox[5] = 0 // 0 :request, 0x80000000: response // mbox[6] = MBOX_TAG_LAST // aligned on 16 mutiple so the 4 first bit can be used by the channel // Should be allocated in the first 2^32bytes volatile uint32_t __attribute__((aligned(16))) mbox[36]; int mbox_call(uint8_t ch, volatile uint32_t *box) { // mbox is 16 aligned uint32_t r = (uint64_t)box | (ch & 0xF); while (*MBOX_STATUS & MBOX_FULL) { asm volatile("nop"); } *MBOX_WRITE = r; while (1) { while (*MBOX_STATUS & MBOX_EMPTY) { asm volatile("nop"); } if (r == *MBOX_READ) /* is it a valid successful response? */ return box[1] == MBOX_RESPONSE; } return 0; }