[M] Change in coreboot[master]: lib/coreboot_table: Simplify API to set up lb_serial

[Hung-Te Lin (Code Review)]

Attention is currently required from: Julius Werner, Arthur Heymans, ron minnich.

Hung-Te Lin has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/68768 )

Change subject: lib/coreboot_table: Simplify API to set up lb_serial
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Patch Set 7:

(1 comment)

File src/lib/coreboot_table.c:

https://review.coreboot.org/c/coreboot/+/68768/comment/24bc7a87_da897af4 
PS7, Line 102: struct lb_serial new_serial = get_lb_serial();
             : 	/* Use the base address as a proxy for an invalid struct */
             : 	if (new_serial.baseaddr == 0)
             : 		return;
             : 
             : 	serial = (struct lb_serial *)lb_new_record(header);
             : 	memcpy(serial, &new_serial, sizeof(*serial));
             : 	serial->tag = LB_TAG_SERIAL;
             : 	serial->size = sizeof(*serial);
             : 	if (serial->type == LB_SERIAL_TYPE_IO_MAPPED)
             : 		lb_add_console(LB_TAG_CONSOLE_SERIAL8250, header);
             : 	else
             : 		lb_add_console(LB_TAG_CONSOLE_SERIAL8250MEM, header);
It's true we can return a struct, but the implementation above is
 - using a hint baseaddr=0 implies invalid
 - assuming the get_lb_serial will only fill partial data
 - overwriting the size

If we're going to change the APIs, I'd rather redefine it as:
  int get_lb_serial(struct lb_serial *serial) {
    serial->type = ...
    return 0;
  }

And then you can do here:

struct lb_serial new_serial = {0};
  new_serial.tag = LB_TAG_SERIAL;
  new_serial.size = sizeof(new_serial);
  if (!get_lb_serial(&new_serial))
    return;
  // allocate the new record, copy serial etc