Update the device pager interface, while keeping the compatibility

layer for old KPI and KBI.  New interface should be used together with
d_mmap_single cdevsw method.

Device pager can be allocated with the cdev_pager_allocate(9)
function, which takes struct cdev_pager_ops, containing
constructor/destructor and page fault handler methods supplied by
driver.

Constructor and destructor, called at the pager allocation and
deallocation time, allow the driver to handle per-object private data.

The pager handler is called to handle page fault on the vm map entry
backed by the driver pager. Driver shall return either the vm_page_t
which should be mapped, or error code (which does not cause kernel
panic anymore). The page handler interface has a placeholder to
specify the access mode causing the fault, but currently PROT_READ is
always passed there.

Sponsored by:	The FreeBSD Foundation
Reviewed by:	alc
MFC after:	1 month

1 files changed, 14 insertions, 0 deletions

diff --git a/sys/vm/vm_pager.h b/sys/vm/vm_pager.h
index c18719a..c361be8 100644
--- a/sys/vm/vm_pager.h
+++ b/sys/vm/vm_pager.h
@@ -192,5 +192,19 @@ vm_pager_page_unswapped(vm_page_t m)
 		(*pagertab[m->object->type]->pgo_pageunswapped)(m);
 }
 
+struct cdev_pager_ops {
+	int (*cdev_pg_fault)(vm_object_t vm_obj, vm_ooffset_t offset,
+	    int prot, vm_page_t *mres);
+	int (*cdev_pg_ctor)(void *handle, vm_ooffset_t size, vm_prot_t prot,
+	    vm_ooffset_t foff, struct ucred *cred, u_short *color);
+	void (*cdev_pg_dtor)(void *handle);
+};
+
+vm_object_t cdev_pager_allocate(void *handle, enum obj_type tp,
+    struct cdev_pager_ops *ops, vm_ooffset_t size, vm_prot_t prot,
+    vm_ooffset_t foff, struct ucred *cred);
+vm_object_t cdev_pager_lookup(void *handle);
+void cdev_pager_free_page(vm_object_t object, vm_page_t m);
+
 #endif				/* _KERNEL */
 #endif				/* _VM_PAGER_ */