Question

I have uint8_t orig[ETH_ALEN];

How can I print it using __printf(3, 4)

which is defined as #define __printf(a, b) __attribute__((format(printf, a, b)))

the Orig should be ethernet hardware address.

Answer 1

You need to construct a format string that’s suitable. The printf() function has no way of printing an array in one go, so you need to split it and print each uint8_t:

__printf("MAC: %02x:%02x:%02x:%02x:%02x:%02x\n",
         orig[0] & 0xff, orig[1] & 0xff, orig[2] & 0xff,
         orig[3] & 0xff, orig[4] & 0xff, orig[5] & 0xff);

The & 0xff is to ensure only 8 bits are sent to printf(); they shouldn’t be needed for an unsigned type like uint8_t though so you can try without too.

This assumes a regular 48-bit MAC, and prints using the conventional colon-separated hex style.