[RFC 2/8] dma-buf: Add a helper to match interconnects between exporter/importer

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

If the importer provides an op for supports_interconnects(), the
exporter starts the matching (or negotiation) process (during
attach) by invoking the supports_interconnects() which would then
call this helper to identify the first common interconnect
supported by both exporter and importer.

Note that whether an interconnect is supported between an
exporter/importer is ultimately determined by the exporter via
the match op it is expected to provide.

Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 drivers/dma-buf/dma-buf.c            | 45 +++++++++++++++++++++++++++-
 include/linux/dma-buf-interconnect.h |  6 ++++
 include/linux/dma-buf.h              |  9 ++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 162642bd53e8..ed48540d1c1d 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -965,8 +965,11 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
 
 	attach->dev = dev;
 	attach->dmabuf = dmabuf;
-	if (importer_ops)
+	if (importer_ops) {
 		attach->peer2peer = importer_ops->allow_peer2peer;
+		if (importer_ops->supports_interconnects)
+			attach->allow_ic = true;
+	}
 	attach->importer_ops = importer_ops;
 	attach->importer_priv = importer_priv;
 
@@ -1680,6 +1683,46 @@ void dma_buf_unmap_interconnect(struct dma_buf_attachment *attach,
 }
 EXPORT_SYMBOL_NS_GPL(dma_buf_unmap_interconnect, "DMA_BUF");
 
+bool dma_buf_match_interconnects(struct dma_buf_attachment *attach,
+				 const struct dma_buf_interconnect_match *exp,
+				 unsigned int exp_ics,
+				 const struct dma_buf_interconnect_match *imp,
+				 unsigned int imp_ics)
+{
+	const struct dma_buf_interconnect *exp_ic, *imp_ic;
+	const struct dma_buf_interconnect_ops *ic_ops;
+	struct dma_buf *dmabuf = attach->dmabuf;
+	unsigned int i, j;
+
+	if (!exp || !imp)
+		return false;
+
+	if (!attach->allow_ic)
+		return false;
+
+	ic_ops = dmabuf->ops->interconnect_ops;
+	if (!ic_ops || !ic_ops->match_interconnect)
+		return false;
+
+	for (i = 0; i < exp_ics; i++) {
+		for (j = 0; j < imp_ics; j++) {
+			exp_ic = exp[i].interconnect;
+			imp_ic = imp[j].interconnect;
+
+			if (exp_ic->type == imp_ic->type) {
+				if (ic_ops->match_interconnect(exp_ic, imp_ic)) {
+					attach->interconnect.type = exp_ic->type;
+					return true;
+				}
+			}
+		}
+	}
+
+	attach->allow_ic = false;
+	return false;
+}
+EXPORT_SYMBOL_NS_GPL(dma_buf_match_interconnects, "DMA_BUF");
+
 #ifdef CONFIG_DEBUG_FS
 static int dma_buf_debug_show(struct seq_file *s, void *unused)
 {
diff --git a/include/linux/dma-buf-interconnect.h b/include/linux/dma-buf-interconnect.h
index 17504dea9691..a72f65ed4806 100644
--- a/include/linux/dma-buf-interconnect.h
+++ b/include/linux/dma-buf-interconnect.h
@@ -20,10 +20,16 @@ struct dma_buf_interconnect {
 	enum dma_buf_interconnect_type type;
 };
 
+struct dma_buf_interconnect_match {
+	const struct dma_buf_interconnect *interconnect;
+};
+
 struct dma_buf_interconnect_ops {
 	int (*map_interconnect)(struct dma_buf_attachment *attach,
 				struct dma_buf_ranges *ranges);
 	void (*unmap_interconnect)(struct dma_buf_attachment *attach,
 				   struct dma_buf_ranges *ranges);
+	bool (*match_interconnect)(const struct dma_buf_interconnect *exp_ic,
+				   const struct dma_buf_interconnect *imp_ic);
 };
 #endif
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index db91c67c00d6..3e6124387f3c 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -479,6 +479,10 @@ struct dma_buf_attach_ops {
 	 * point to the new location of the DMA-buf.
 	 */
 	void (*move_notify)(struct dma_buf_attachment *attach);
+
+	bool (*supports_interconnects)(struct dma_buf_attachment *attach,
+				       const struct dma_buf_interconnect_match *,
+				       unsigned int num_ics);
 };
 
 /**
@@ -599,6 +603,11 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
 struct dma_buf_ranges *dma_buf_map_interconnect(struct dma_buf_attachment *);
 void dma_buf_unmap_interconnect(struct dma_buf_attachment *,
 				struct dma_buf_ranges *);
+bool dma_buf_match_interconnects(struct dma_buf_attachment *attach,
+				 const struct dma_buf_interconnect_match *,
+				 unsigned int exp_ics,
+				 const struct dma_buf_interconnect_match *,
+				 unsigned int imp_ics);
 
 void dma_buf_move_notify(struct dma_buf *dma_buf);
 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
-- 
2.50.1