`_cyw43_write_reg` assigns to `last_size`/`_header`/`_backplane_window` variables which are never used

[dpgeorge]

The cyw43 SPI transport _cyw43_write_reg() function has this bit of code in it:

    if (fn == BACKPLANE_FUNCTION) {
        // In case of f1 overflow
        self->last_size = 8;
        self->last_header[0] = buf[0];
        self->last_header[1] = buf[1];
        self->last_backplane_window = self->cur_backplane_window;
    }

(self is a cyw43 driver instance.)

These last_xxx variables are never used by cyw43-driver because F1_OVERFLOW_CHANGE is permanently disabled. And that feature even has comments that it never actually worked.

It would be good to get rid of these variables in the cyw43 driver data structure, to save a little bit of RAM and clean it up. So I propose removing their use from this sdk.

Alternatively the above code could be guarded by a #if F1_OVERFLOW_CHANGE, but then that config option would need to be made public, probably named CYW43_F1_OVERFLOW_CHANGE.

[peterharperuk]

Yes - we should get rid of all that junk.

[dpgeorge]

we should get rid of all that junk

Can I just remove all the F1_OVERFLOW_CHANGE code?

[peterharperuk]

Yes please - I meant to raise a PR to remove it - but kept forgetting. It was originally a suggestion from Infineon I believe. I'm not sure it ever actually worked and we managed to fix the issue another way and have never used this code again.

[dpgeorge]

Yes please - I meant to raise a PR to remove it - but kept forgetting

OK, done in georgerobotics/cyw43-driver#134

[lurch]

Fixed in develop