[flashrom] [GSoC 2022] Restructure Shutdown Function

[Joursoir]

Good day,

I am a student and very interested in flashrom. I fit the description 
of experienced C programmer. Open-source and low-level programming are
my interests. I already have real experience with flashrom (CH341A
programmer + chip "MX25L6436E") and want to become a GSoC 2022
contributor in this project.

I find the "Restructure Shutdown Function" project interestring to me.
But right now it has no mentors. Maybe someone from the mailing can
help me.

I have gone through sources and understand how things are now. The
project description says "have a defined shutdown function in the
programmer API". But we already have it. It's programmer_shutdown().
Or no?

The first and easiest thing that comes to my mind is to refuse using
callbacks and use enums, thusly:

enum shutdown_func {
    SERPROG = 1 << 0,
    SPI = 1 << 1,
    ...
};

int programmer_shutdown(enum shutdown_func execfunc)
{
    ...

if(execfunc & SERPROG)
        ret |= serprog_shutdown(...);

if(execfunc & SPI) {
        /* the problem is that SPI programmers have own shutdown funcs,
           like dlc5_shutdown, byteblaster_shutdown, stlinkv3_spi_shutdown,
           so use struct spi_master, that contains shutdown callback */
        ret |= spi_master_shutdown(...);
    }

...
}

This system has disadvantages, but it'll make easier to track the code
flow. What are the potential problems in this implementation?

What's with struct flashrom_programmer? Is not implemented yet?

I would appreciate any feedback.