make dmem a bit more readable

1 files changed, 36 insertions, 46 deletions

diff --git a/src/dmem.c b/src/dmem.c
index ca311c2..b02b71b 100644
--- a/src/dmem.c
+++ b/src/dmem.c
@@ -17,48 +17,48 @@ static struct mem_region_root pre_ram = { 0 };
 /** Region after RAM. */
 static struct mem_region_root post_ram = { 0 };
 
-pm_t __pre_base = 0;
-pm_t __pre_top = 0;
-pm_t __post_base = 0;
-pm_t __post_top = 0;
-
 stat_t init_devmem(pm_t ram_base, pm_t ram_top)
 {
-	pm_t mem_top = (pm_t)-1;
-
-	__pre_base = 0;
-	__pre_top = ram_base - 1;
+	size_t pre_pages = __pages(ram_base);
+	size_t ram_pages = __pages(ram_top - ram_base);
+	/* -1 being the effective highest address possible */
+	size_t post_pages = __pages(-1) - ram_pages - pre_pages;
 
-	__post_base = ram_top;
-	__post_top = mem_top;
+	init_region(&pre_ram, 0, pre_pages);
+	init_region(&post_ram, ram_top, post_pages);
+	return OK;
+}
 
-	size_t pre_pages = __pages(__pre_top);
-	size_t post_pages = __pages(__post_top) - __pages(__post_base);
+/**
+ * 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;
 
-	init_region(&pre_ram, __pre_base, pre_pages);
-	init_region(&post_ram, __post_base, post_pages);
+	if (addr > (get_ram_base() + get_ram_size()))
+		return &post_ram;
 
-	return OK;
+	return NULL;
 }
 
-vm_t alloc_devmem(struct tcb *t, pm_t dev_start, size_t bytes, vmflags_t flags)
+vm_t alloc_devmem(struct tcb *t, pm_t start, size_t bytes, vmflags_t flags)
 {
 	hard_assert(t && is_proc(t), ERR_INVAL);
 
-	struct mem_region_root *region = NULL;
-	if (dev_start < __pre_top)
-		region = &pre_ram;
-
-	else if (dev_start > __post_base)
-		region = &post_ram;
-	else
+	struct mem_region_root *region = __select_region(start);
+	if (!region)
 		return NULL;
 
 	vm_t v = alloc_region(region, bytes, &bytes, flags);
 	if (!v)
 		return NULL;
 
-	if (map_fixed_region(t->proc.vmem, v, dev_start, bytes, flags)) {
+	if (map_fixed_region(t->proc.vmem, v, start, bytes, flags)) {
 		unmap_region(t->proc.vmem, v, bytes);
 		free_region(region, v);
 		return NULL;
@@ -67,36 +67,26 @@ vm_t alloc_devmem(struct tcb *t, pm_t dev_start, size_t bytes, vmflags_t flags)
 	return v;
 }
 
-stat_t free_devmem(struct tcb *t, vm_t dev_start)
+stat_t free_devmem(struct tcb *t, vm_t start)
 {
 	hard_assert(t && is_proc(t), ERR_INVAL);
+	pm_t addr = 0;
+	stat_vpage(t->proc.vmem, start, &addr, NULL, NULL);
 
-	pm_t dev_paddr = 0;
-	stat_vpage(t->proc.vmem, dev_start, &dev_paddr, 0, 0);
-
-	if (dev_paddr >= __pre_top && dev_paddr <= __post_base)
-		return ERR_ADDR;
+	struct mem_region_root *region = __select_region((pm_t)__pa(addr));
+	if (!region)
+		return ERR_INVAL;
 
-	struct mem_region *m = 0;
-	if (dev_paddr < __pre_top)
-		m = find_used_region(&pre_ram, dev_start);
-
-	else if (dev_paddr > __post_base)
-		m = find_used_region(&post_ram, dev_start);
 
+	struct mem_region *m = find_used_region(region, start);
 	if (!m)
 		return ERR_NF;
 
-	vm_t start = __addr(m->start);
+	vm_t base = __addr(m->start);
 	vm_t end = __addr(m->end);
-	size_t size = end - start;
-	unmap_fixed_region(t->proc.vmem, start, size);
-
-	if (dev_paddr < __pre_top)
-		free_region(&pre_ram, dev_start);
-
-	else if (dev_paddr > __post_base)
-		free_region(&post_ram, dev_start);
+	size_t size = end - base;
+	unmap_fixed_region(t->proc.vmem, base, size);
 
+	free_region(region, base);
 	return OK;
 }