Introduce the concept of busdma tag templates. A template can be allocated

off the stack, initialized to default values, and then filled in with
driver-specific values, all without having to worry about the numerous
other fields in the tag. The resulting template is then passed into
busdma and the normal opaque tag object created.  See the man page for
details on how to initialize a template.

Templates do not support tag filters.  Filters have been broken for many
years, and only existed for an ancient make/model of hardware that had a
quirky DMA engine.  Instead of breaking the ABI/API and changing the
arugment signature of bus_dma_tag_create() to remove the filter arguments,
templates allow us to ignore them, and also significantly reduce the
complexity of creating and managing tags.

Reviewed by:	imp, kib
Differential Revision:	https://reviews.freebsd.org/D22906

2 files changed, 102 insertions, 0 deletions

diff --git a/sys/arm/arm/busdma_machdep-v4.c b/sys/arm/arm/busdma_machdep-v4.c
index 649ce05fdb38..6c1fd6a9e999 100644
--- a/sys/arm/arm/busdma_machdep-v4.c
+++ b/sys/arm/arm/busdma_machdep-v4.c
@@ -501,6 +501,57 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	return (error);
 }
 
+void
+bus_dma_template_init(bus_dma_tag_template_t *t, bus_dma_tag_t parent)
+{
+
+	if (t == NULL)
+		return;
+
+	t->parent = parent;
+	t->alignment = 1;
+	t->boundary = 0;
+	t->lowaddr = t->highaddr = BUS_SPACE_MAXADDR;
+	t->maxsize = t->maxsegsize = BUS_SPACE_MAXSIZE;
+	t->nsegments = BUS_SPACE_UNRESTRICTED;
+	t->lockfunc = NULL;
+	t->lockfuncarg = NULL;
+	t->flags = 0;
+}
+
+int
+bus_dma_template_tag(bus_dma_tag_template_t *t, bus_dma_tag_t *dmat)
+{
+
+	if (t == NULL || dmat == NULL)
+		return (EINVAL);
+
+	return (bus_dma_tag_create(t->parent, t->alignment, t->boundary,
+	    t->lowaddr, t->highaddr, NULL, NULL, t->maxsize,
+	    t->nsegments, t->maxsegsize, t->flags, t->lockfunc, t->lockfuncarg,
+	    dmat));
+}
+
+void
+bus_dma_template_clone(bus_dma_tag_template_t *t, bus_dma_tag_t dmat)
+{
+
+	if (t == NULL || dmat == NULL)
+		return;
+
+	t->parent = dmat->parent;
+	t->alignment = dmat->alignment;
+	t->boundary = dmat->boundary;
+	t->lowaddr = dmat->lowaddr;
+	t->highaddr = dmat->highaddr;
+	t->maxsize = dmat->maxsize;
+	t->nsegments = dmat->nsegments;
+	t->maxsegsize = dmat->maxsegsz;
+	t->flags = dmat->flags;
+	t->lockfunc = dmat->lockfunc;
+	t->lockfuncarg = dmat->lockfuncarg;
+}
+
 int
 bus_dma_tag_set_domain(bus_dma_tag_t dmat, int domain)
 {
diff --git a/sys/arm/arm/busdma_machdep-v6.c b/sys/arm/arm/busdma_machdep-v6.c
index fa79b1d913d0..6e2fb4a0d8f6 100644
--- a/sys/arm/arm/busdma_machdep-v6.c
+++ b/sys/arm/arm/busdma_machdep-v6.c
@@ -575,6 +575,57 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	return (error);
 }
 
+void
+bus_dma_template_init(bus_dma_tag_template_t *t, bus_dma_tag_t parent)
+{
+
+	if (t == NULL)
+		return;
+
+	t->parent = parent;
+	t->alignment = 1;
+	t->boundary = 0;
+	t->lowaddr = t->highaddr = BUS_SPACE_MAXADDR;
+	t->maxsize = t->maxsegsize = BUS_SPACE_MAXSIZE;
+	t->nsegments = BUS_SPACE_UNRESTRICTED;
+	t->lockfunc = NULL;
+	t->lockfuncarg = NULL;
+	t->flags = 0;
+}
+
+int
+bus_dma_template_tag(bus_dma_tag_template_t *t, bus_dma_tag_t *dmat)
+{
+
+	if (t == NULL || dmat == NULL)
+		return (EINVAL);
+
+	return (bus_dma_tag_create(t->parent, t->alignment, t->boundary,
+	    t->lowaddr, t->highaddr, NULL, NULL, t->maxsize,
+	    t->nsegments, t->maxsegsize, t->flags, t->lockfunc, t->lockfuncarg,
+	    dmat));
+}
+
+void
+bus_dma_template_clone(bus_dma_tag_template_t *t, bus_dma_tag_t dmat)
+{
+
+	if (t == NULL || dmat == NULL)
+		return;
+
+	t->parent = dmat->parent;
+	t->alignment = dmat->alignment;
+	t->boundary = dmat->boundary;
+	t->lowaddr = dmat->lowaddr;
+	t->highaddr = dmat->highaddr;
+	t->maxsize = dmat->maxsize;
+	t->nsegments = dmat->nsegments;
+	t->maxsegsize = dmat->maxsegsz;
+	t->flags = dmat->flags;
+	t->lockfunc = dmat->lockfunc;
+	t->lockfuncarg = dmat->lockfuncarg;
+}
+
 int
 bus_dma_tag_set_domain(bus_dma_tag_t dmat, int domain)
 {