linux-kernel - Please revert the addition of the AMD QDMA driver

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Message-ID: <20240916074051.GA18902@lst.de>
Date: Mon, 16 Sep 2024 09:40:51 +0200
From: Christoph Hellwig <hch@....de>
To: Vinod Koul <vkoul@...nel.org>, Nishad Saraf <nishads@....com>,
	Lizhi Hou <lizhi.hou@....com>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Please revert the addition of the AMD QDMA driver

Hi Vinod,

I just noticed you added the AMD QDMA driver for this merge window,
which is completely broken in terms of DMA API usage by using the
private get/set_dma_ops APIs.  These were never for driver use (
and I've been working for years to fix the few abusers), but with the
DMA changes in 6.12 it actually can't work at all, as the dma-iommu
driver now also sets NULL DMA ops in addition to dma-direct.

As a reminder drivers must never try to inherit dma settings from
one device or another, instead pass the actual DMA device to whatever
layer does the DMA mapping.  Without that you break all kinds of
thing.