For the slave caps retrieval to be really useful, most drivers need to
implement it.

Hence, we need to be slightly more aggressive, and trigger a warning at
registration time for drivers that don't fill their caps infos in order to
encourage them to implement it.

Signed-off-by: Maxime Ripard <redacted>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/dma/dmaengine.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 98e9431f85ec..300c8cd2786c 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c

@@ -827,6 +827,9 @@ int dma_async_device_register(struct dma_device *device)
        BUG_ON(!device->device_issue_pending);
        BUG_ON(!device->dev);

+       WARN(dma_has_cap(DMA_SLAVE, device->cap_mask) && !device->directions,
+            "this driver doesn't support generic slave capabilities reporting\n");
+
        /* note: this only matters in the
         * CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH=n case
         */