Mega busdma API commit.

Add two new arguments to bus_dma_tag_create(): lockfunc and lockfuncarg.
Lockfunc allows a driver to provide a function for managing its locking
semantics while using busdma.  At the moment, this is used for the
asynchronous busdma_swi and callback mechanism.  Two lockfunc implementations
are provided: busdma_lock_mutex() performs standard mutex operations on the
mutex that is specified from lockfuncarg.  dftl_lock() is a panic
implementation and is defaulted to when NULL, NULL are passed to
bus_dma_tag_create().  The only time that NULL, NULL should ever be used is
when the driver ensures that bus_dmamap_load() will not be deferred.
Drivers that do not provide their own locking can pass
busdma_lock_mutex,&Giant args in order to preserve the former behaviour.

sparc64 and powerpc do not provide real busdma_swi functions, so this is
largely a noop on those platforms.  The busdma_swi on is64 is not properly
locked yet, so warnings will be emitted on this platform when busdma
callback deferrals happen.

If anyone gets panics or warnings from dflt_lock() being called, please
let me know right away.

Reviewed by:	tmm, gibbs

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/alpha/isa/isa_dma.c b/sys/alpha/isa/isa_dma.c
index ef671be..22eea8a 100644
--- a/sys/alpha/isa/isa_dma.c
+++ b/sys/alpha/isa/isa_dma.c
@@ -53,6 +53,8 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/malloc.h>
+#include <sys/lock.h>
+#include <sys/mutex.h>
 #include <sys/bus.h>
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -131,6 +133,8 @@ isa_dmainit(chan, bouncebufsize)
 			       /*maxsize*/bouncebufsize,
 			       /*nsegments*/1, /*maxsegz*/0x3ffff,
 			       /*flags*/BUS_DMA_ISA,
+			       /*lockfunc*/busdma_lock_mutex,
+			       /*lockarg*/&Giant,
 			       &dma_tag[chan]) != 0) {
 		panic("isa_dmainit: unable to create dma tag\n");
 	}