Adding flash before erasing and writing into flash - c

Question

In a program to erase and write into flash, I donot understand the lines
struct kinetis_flash *kf = calloc(1, sizeof(*kf));
struct target_flash *f = &kf->f;
from the below section of the code. And the whole program can be found at https://github.com/blacksphere/blackmagic/blob/master/src/target/kinetis.c
struct kinetis_flash {
struct target_flash f;
uint8_t write_len;
};
static void kl_gen_add_flash(target *t, uint32_t addr, size_t length,
size_t erasesize, size_t write_len)
{
struct kinetis_flash *kf = calloc(1, sizeof(*kf));
struct target_flash *f = &kf->f;
f->start = addr;
f->length = length;
f->blocksize = erasesize;
f->erase = kl_gen_flash_erase;
f->write = kl_gen_flash_write;
f->done = kl_gen_flash_done;
f->erased = 0xff;
kf->write_len = write_len;
target_add_flash(t, f);
}
It would be great if someone helps me understanding above tw lines, thanks in advance.Many targets for example KL25, K22, K64 can be accordingly used what i understood from the project. Are those two lines storing target specific specifications for flash?
In general we donot need to allocate any space for flash right using calloc or malloc like we do it for RAM.

Answer 1

The code in question extends GDB, allowing it to use various JTAG or Serial Wire interfaces to program and debug certain ARM devices. Identifying the attached devices flash device is a time consuming and disruptive (as-in can't run device code) task, so you only want to do it once, hence the local RAM allocation for storing the type and current state of the attached flash.

Answer 2

This line
struct kinetis_flash *kf = calloc(1, sizeof(*kf));
is a dynamic allocation of a struct kinetis_flash somewhere in RAM. It's probably used for holding information about a flash device present in the system.
This line
struct target_flash *f = &kf->f;
makes f point to the struct target_flash - named f - inside struct kinetis_flash so that you can write to it using f->some_var = ...
So the whole function is simply creating and initializing an object of type struct kinetis_flash
Though the code is correct, it's (IMO) a bit confusing to have a variable f pointing to f inside a struct. Perhaps a name like ptr_f would be more clear.
Also notice that the code is equivalent to:
static void kl_gen_add_flash(target *t, uint32_t addr, size_t length,
size_t erasesize, size_t write_len)
{
struct kinetis_flash *kf = calloc(1, sizeof(*kf));
kf->f.start = addr;
kf->f.length = length;
...
}