linux-kernel - [PATCH 1/4] scsi: check that busses support the DMA API before setting dma parameters

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Message-ID: <20240824034925.1163244-2-hch@lst.de>
Date: Sat, 24 Aug 2024 05:49:12 +0200
From: Christoph Hellwig <hch@....de>
To: iommu@...ts.linux.dev
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>,
	Robin Murphy <robin.murphy@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	dmaengine@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	linux-media@...r.kernel.org,
	linux-mmc@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH 1/4] scsi: check that busses support the DMA API before setting dma parameters

We'll start throwing warnings soon when dma_set_seg_boundary and
dma_set_max_seg_size are called on devices for buses that don't fully
support the DMA API.  Prepare for that by making the calls in the SCSI
midlayer conditional.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/scsi/scsi_lib.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3958a6d14bf457..7f0394c4492033 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1988,8 +1988,15 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim)
 	if (shost->no_highmem)
 		lim->features |= BLK_FEAT_BOUNCE_HIGH;
 
-	dma_set_seg_boundary(dev, shost->dma_boundary);
-	dma_set_max_seg_size(dev, shost->max_segment_size);
+	/*
+	 * Propagate the DMA formation properties to the dma-mapping layer as
+	 * a courtesy service to the LLDDs.  This needs to check that the buses
+	 * actually support the DMA API first, though.
+	 */
+	if (dev->dma_parms) {
+		dma_set_seg_boundary(dev, shost->dma_boundary);
+		dma_set_max_seg_size(dev, shost->max_segment_size);
+	}
 }
 EXPORT_SYMBOL_GPL(scsi_init_limits);
 
-- 
2.43.0