[PATCH v2] dmaengine: xilinx: xdma: use kzalloc_flex()

[Rosen Penev]

Change desc_blocks to a flexible array member so the descriptor and
its block array are allocated together, removing one allocation and
its error handling.

Add __counted_by for extra runtime analysis, and set dblk_num right
after allocation which is already done by kzalloc_flex() for GCC >= 15.

Assisted-by: LLM
Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>
---
 drivers/dma/xilinx/xdma.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index 8d4a5d14e8db..16d202722245 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -81,7 +81,6 @@ struct xdma_chan {
  * @vdesc: Virtual DMA descriptor
  * @chan: DMA channel pointer
  * @dir: Transferring direction of the request
- * @desc_blocks: Hardware descriptor blocks
  * @dblk_num: Number of hardware descriptor blocks
  * @desc_num: Number of hardware descriptors
  * @completed_desc_num: Completed hardware descriptors
@@ -91,12 +90,12 @@ struct xdma_chan {
  * @period_size: Size of a period in bytes in cyclic transfers
  * @frames_left: Number of frames left in interleaved DMA transfer
  * @error: tx error flag
+ * @desc_blocks: Hardware descriptor blocks
  */
 struct xdma_desc {
 	struct virt_dma_desc		vdesc;
 	struct xdma_chan		*chan;
 	enum dma_transfer_direction	dir;
-	struct xdma_desc_block		*desc_blocks;
 	u32				dblk_num;
 	u32				desc_num;
 	u32				completed_desc_num;
@@ -106,6 +105,7 @@ struct xdma_desc {
 	u32				period_size;
 	u32				frames_left;
 	bool				error;
+	struct xdma_desc_block		desc_blocks[] __counted_by(dblk_num);
 };
 
 #define XDMA_DEV_STATUS_REG_DMA		BIT(0)
@@ -255,7 +255,6 @@ static void xdma_free_desc(struct virt_dma_desc *vdesc)
 			      sw_desc->desc_blocks[i].virt_addr,
 			      sw_desc->desc_blocks[i].dma_addr);
 	}
-	kfree(sw_desc->desc_blocks);
 	kfree(sw_desc);
 }
 
@@ -276,26 +275,22 @@ xdma_alloc_desc(struct xdma_chan *chan, u32 desc_num, bool cyclic)
 	void *addr;
 	int i, j;
 
-	sw_desc = kzalloc_obj(*sw_desc, GFP_NOWAIT);
+	dblk_num = DIV_ROUND_UP(desc_num, XDMA_DESC_ADJACENT);
+	sw_desc = kzalloc_flex(*sw_desc, desc_blocks, dblk_num, GFP_NOWAIT);
 	if (!sw_desc)
 		return NULL;
 
+	sw_desc->dblk_num = dblk_num;
 	sw_desc->chan = chan;
 	sw_desc->desc_num = desc_num;
 	sw_desc->cyclic = cyclic;
 	sw_desc->error = false;
-	dblk_num = DIV_ROUND_UP(desc_num, XDMA_DESC_ADJACENT);
-	sw_desc->desc_blocks = kzalloc_objs(*sw_desc->desc_blocks, dblk_num,
-					    GFP_NOWAIT);
-	if (!sw_desc->desc_blocks)
-		goto failed;
 
 	if (cyclic)
 		control = XDMA_DESC_CONTROL_CYCLIC;
 	else
 		control = XDMA_DESC_CONTROL(1, 0);
 
-	sw_desc->dblk_num = dblk_num;
 	for (i = 0; i < sw_desc->dblk_num; i++) {
 		addr = dma_pool_alloc(chan->desc_pool, GFP_NOWAIT, &dma_addr);
 		if (!addr)
-- 
2.56.0