/* SPDX-License-Identifier: copyleft-next-0.3.1 */
/* Copyright 2021 - 2022, Kim Kuparinen < kimi.h.kuparinen@gmail.com > */

/**
 * @file dmem.c
 * Handle device memory, i.e. anything outside the physical RAM.
 *
 * \todo Handle NUMA.
 */

#include <kmi/assert.h>
#include <kmi/dmem.h>

/** Region before RAM. */
static struct mem_region_root pre_ram = { 0 };

/** Region after RAM. */
static struct mem_region_root post_ram = { 0 };

stat_t init_devmem(pm_t ram_base, pm_t ram_top)
{
	init_region(&pre_ram, 0, ram_base, 0);
	init_region(&post_ram, ram_top, -1, 0);
	return OK;
}

/**
 * Select between the area before RAM or after RAM, depending on \p addr.
 *
 * @param addr Physical address of device.
 * @return Corresponding device memory region or NULL if \p addr is within RAM.
 */
static struct mem_region_root *__select_region(pm_t addr)
{
	if (addr < get_ram_base())
		return &pre_ram;

	if (addr > (get_ram_base() + get_ram_size()))
		return &post_ram;

	return NULL;
}

vm_t alloc_devmem(struct tcb *t, pm_t start, size_t bytes, vmflags_t flags)
{
	assert(t && is_proc(t));

	struct mem_region_root *region = __select_region(start);
	if (!region)
		return NULL;

	/* carve out physical region (vm_t is misleading, this region is
	 * physical memory) */
	vm_t p = alloc_fixed_region(region, start, bytes, &bytes, flags);
	if (!p)
		return NULL;

	/* carve out virtual region */
	vm_t v = alloc_region(&t->uvmem.region, bytes, &bytes, flags | MR_DEV);
	if (!v) {
		free_region(region, p);
		return NULL;
	}

	/* convert from literal physical address to direct mapping address,
	 * which map_* expects (kind of annoying to deal with, admittedly, is
	 * there maybe a better way to handle these things?) */
	p = (pm_t)__va(p);
	if (map_fixed_region(t->proc.vmem, v, p, bytes, flags)) {
		unmap_region(t->proc.vmem, v, bytes);
		free_region(&t->uvmem.region, v);
		free_region(region, p);
		return NULL;
	}

	return v;
}

stat_t free_known_devmem(struct tcb *t, struct mem_region *m)
{
	assert(t && is_proc(t));

	/* ensure region is a device memory region and is currently not shared */
	assert(is_set(m->flags, MR_DEV));
	assert(m->pid != 0 || m->refcount == 1);

	pm_t addr = 0;
	stat_vpage(t->proc.vmem, __addr(m->start), &addr, NULL, NULL);

	/* free physical device memory */
	pm_t p = (pm_t)__pa(addr);
	struct mem_region_root *region = __select_region(p);
	if (!region)
		return ERR_INVAL;

	free_region(region, p);

	/* free virtual allocation associated with device mem */
	vm_t base = __addr(m->start);
	vm_t end = __addr(m->end);

	/* free virtual memory associated with physical mapping */
	size_t size = end - base;
	unmap_fixed_region(t->proc.vmem, base, size);

	free_known_region(&t->uvmem.region, m);
	return OK;
}

stat_t free_devmem(struct tcb *t, vm_t start)
{
	assert(t && is_proc(t));
	struct mem_region *m = find_used_region(&t->uvmem.region, start);
	if (!m)
		return ERR_NF;

	/* not a devmem region */
	if (!is_set(m->flags, MR_DEV))
		return ERR_INVAL;

	/* mapping is shared, can't free right now */
	if (m->pid == 0 && m->refcount > 1)
		return ERR_INVAL;

	stat_t ret = free_known_devmem(t, m);
	if (ret)
		return ret;

	free_known_region(&t->uvmem.region, m);
	return OK;
}