DFU: How to handle end of flash during a DFU upload ?

[iabdalkader]

In tud_dfu_upload_cb how do I indicate to TinyUSB that the end of flash/partition has been reached ? According to the specs:

The host sends DFU_UPLOAD requests to the device until it responds with a short frame as an end of file (EOF) indicator.

But how do I respond with a "short frame" ?

I have something like the following:

uint16_t tud_dfu_upload_cb(uint8_t alt, uint16_t block_num, uint8_t *p_dst, uint16_t length) {
    uint8_t *p_src = (uint8_t *) (part->start + (block_num * CFG_TUD_DFU_XFER_BUFSIZE));
    if (((uint32_t) p_src + length) > part->limit) {
        return 0;
    }
    memcpy(p_dst, p_src, length);
    return length;
}

But this causes dfu-util to timeout on the host's side after getting stuck for a while:

DFU mode device DFU version 0101
Device returned transfer size 512
Copying data from DFU device to PC
Upload	[======================== ]  99%      3079168 bytesdfu-util: 
Error during upload (LIBUSB_ERROR_TIMEOUT)
Upload	[======================== ]  99%      4325376 bytes
Received a total of 4325376 bytes

With this I can upload the firmware, but the device will not reset since it timed out.

[iabdalkader]

To answer my question, one just needs to return a short frame 😅