1 files changed, 44 insertions, 0 deletions

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index cb286b1acdb6..5692bc3afd39 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -370,6 +370,33 @@ struct dma_slave_config {
 	unsigned int slave_id;
 };
 
+/* struct dma_slave_caps - expose capabilities of a slave channel only
+ *
+ * @src_addr_widths: bit mask of src addr widths the channel supports
+ * @dstn_addr_widths: bit mask of dstn addr widths the channel supports
+ * @directions: bit mask of slave direction the channel supported
+ * 	since the enum dma_transfer_direction is not defined as bits for each
+ * 	type of direction, the dma controller should fill (1 << <TYPE>) and same
+ * 	should be checked by controller as well
+ * @cmd_pause: true, if pause and thereby resume is supported
+ * @cmd_terminate: true, if terminate cmd is supported
+ *
+ * @max_sg_nr: maximum number of SG segments supported
+ * 	0 for no maximum
+ * @max_sg_len: maximum length of a SG segment supported
+ * 	0 for no maximum
+ */
+struct dma_slave_caps {
+	u32 src_addr_widths;
+	u32 dstn_addr_widths;
+	u32 directions;
+	bool cmd_pause;
+	bool cmd_terminate;
+
+	u32 max_sg_nr;
+	u32 max_sg_len;
+};
+
 static inline const char *dma_chan_name(struct dma_chan *chan)
 {
 	return dev_name(&chan->dev->device);
@@ -532,6 +559,7 @@ struct dma_tx_state {
  *	struct with auxiliary transfer status information, otherwise the call
  *	will just return a simple status code
  * @device_issue_pending: push pending transactions to hardware
+ * @device_slave_caps: return the slave channel capabilities
  */
 struct dma_device {
 
@@ -597,6 +625,7 @@ struct dma_device {
 					    dma_cookie_t cookie,
 					    struct dma_tx_state *txstate);
 	void (*device_issue_pending)(struct dma_chan *chan);
+	int (*device_slave_caps)(struct dma_chan *chan, struct dma_slave_caps *caps);
 };
 
 static inline int dmaengine_device_control(struct dma_chan *chan,
@@ -670,6 +699,21 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
 	return chan->device->device_prep_interleaved_dma(chan, xt, flags);
 }
 
+static inline int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
+{
+	if (!chan || !caps)
+		return -EINVAL;
+
+	/* check if the channel supports slave transactions */
+	if (!test_bit(DMA_SLAVE, chan->device->cap_mask.bits))
+		return -ENXIO;
+
+	if (chan->device->device_slave_caps)
+		return chan->device->device_slave_caps(chan, caps);
+
+	return -ENXIO;
+}
+
 static inline int dmaengine_terminate_all(struct dma_chan *chan)
 {
 	return dmaengine_device_control(chan, DMA_TERMINATE_ALL, 0);