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Date: Sun, 28 Apr 2024 21:36:32 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Chen Ni <nichen@iscas.ac.cn>
Cc: inki.dae@samsung.com, sw0312.kim@samsung.com, kyungmin.park@samsung.com,
	airlied@gmail.com, daniel@ffwll.ch, krzk@kernel.org,
	alim.akhtar@samsung.com, m.szyprowski@samsung.com,
	dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/exynos: Add check for dma_set_max_seg_size
Message-ID: <Zi8j0J9PoOiMrA6H@infradead.org>
References: <20240429023833.1869154-1-nichen@iscas.ac.cn>
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On Mon, Apr 29, 2024 at 10:38:33AM +0800, Chen Ni wrote:
> Add check for the return value of dma_set_max_seg_size() and return
> the error if it fails in order to catch the error.
> 
> Fixes: ddfd4ab6bb08 ("drm/exynos: Fix dma_parms allocation")
> Signed-off-by: Chen Ni <nichen@iscas.ac.cn>

With my dma-mapping hat maintainer on I think we should remove the
return value from it.  It can only return -EIO or 0, and the first
only if the bus has not set up a dma_params structure for the device.
I'd much rather WARN_ON() on that, as it is is a grave error to either
call dma_set_max_seg_size on a device that is on a bus that doesn't
support DMA at all, or for the bus maintainer to accidentlaly drop it.

Feel free to add the patch if exynos has a strict error checking policy,
but it's rather pointless and I'll add removing the return value to my
ever growing TODO list.