Move hackrf_core.x driver instances to drivers.x (2/3)

[antoinevg]

Depends on #1705

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[mossmann]

I wonder if these would be better in hackrf_usb.c or distributed through various source files instead of continuing to lump them together into a common .c file, but I'll let @martinling make that decision later if this doesn't work for his effort. I think this is fine for now.

[martinling]

For integration into PortaPack firmware, the following bits of drivers.c are problematic:

radio

radio_t radio = {
        .sample_rate_cb = sample_rate_set,
};

The reason for the sample_rate_cb field is to allow different clock generator logic to be used - in particular the existing clock_manager.cpp implementation in the PortaPack firmware, which has extra features. Setting the callback here in drivers.c adds an unnecessary dependency on our own clock_gen.c, even if the sample_rate_cb is changed at runtime.

For this reason, I think the radio instance definition should be somewhere under firmware/hackrf_usb.

That said, I'm working on making it possible for our clock_gen.c to replace clock_manager.cpp entirely, which seems like a better way forward given all the precision improvements made there recently. so this is probably a temporary issue.

spi_flash

w25q80bv_driver_t spi_flash = {
        .bus = &spi_bus_ssp0,
        .target_init = w25q80bv_target_init,
};

This adds an unnecessary dependency on w25q80bv_target.c which won't be used in a PortaPack build, since the SPI flash is kept in SPIFI mode there and we access the SPI flash via the memory mapping.

Suggestion

I agreed with the decision to merge this, to advance the process of breaking up hackrf_core, but going forward, I think I'd be inclined to also break up drivers.c, and distribute the instances into the drivers themselves, e.g:

• i2c0, i2c1 -> i2c_bus.c
• ssp_config_max283x, max283x -> max283x.c
• clock_gen -> clock_gen.c, or si5351.c
• ...etc

We can't use the instances without their drivers, and it's hard to see a scenario where we'd want the drivers without their instances.