staging: comedi: complain if dma buffer allocation not supported

When allocating a buffer to support asynchronous comedi commands, if a
DMA coherent buffer was requested but `CONFIG_HAS_DMA` is undefined,
bail out of local helper function `__comedi_buf_alloc()` with an error
message.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index b6cd67ad55d1..d4be0e68509b 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -76,6 +76,12 @@ static void __comedi_buf_alloc(struct comedi_device *dev,
         struct comedi_buf_page *buf;
         unsigned i;
 
+        if (!IS_ENABLED(CONFIG_HAS_DMA) && s->async_dma_dir != DMA_NONE) {
+                dev_err(dev->class_dev,
+                        "dma buffer allocation not supported\n");
+                return;
+        }
+
         async->buf_page_list = vzalloc(sizeof(*buf) * n_pages);
         if (async->buf_page_list)
                 pages = vmalloc(sizeof(struct page *) * n_pages);