linux-kernel - Re: [PATCH v2 14/22] media: rockchip: rga: support external iommus

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Message-ID: <11c7e1c0f9e71978d9dea6b1af067e38d9a2509a.camel@ndufresne.ca>
Date: Wed, 07 Jan 2026 09:24:25 -0500
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Sven Püschel <s.pueschel@...gutronix.de>, Jacob Chen
	 <jacob-chen@...wrt.com>, Ezequiel Garcia <ezequiel@...guardiasur.com.ar>, 
 Mauro Carvalho Chehab
	 <mchehab@...nel.org>, Heiko Stuebner <heiko@...ech.de>, Rob Herring
	 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	 <conor+dt@...nel.org>
Cc: linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v2 14/22] media: rockchip: rga: support external iommus

Hi,

Le mercredi 07 janvier 2026 à 15:19 +0100, Sven Püschel a écrit :
> > > @@ -95,13 +96,16 @@ queue_init(void *priv, struct vb2_queue *src_vq,
> > > struct vb2_queue *dst_vq)
> > >    	src_vq->io_modes = VB2_MMAP | VB2_DMABUF;
> > >    	src_vq->drv_priv = ctx;
> > >    	src_vq->ops = &rga_qops;
> > > -	src_vq->mem_ops = &vb2_dma_sg_memops;
> > > +	src_vq->mem_ops = &vb2_dma_contig_memops;
> > That's a bit I'm less knowledgeable here, since I never used the sg_memops
> > in
> > any of my work, but what is the consequence ? (appart from gaining external
> > iommu support)
> 
> This is only for the external iommu support, which uses the 
> vb2_dma_contig_plane_dma_addr function to get a single linear address 
> (instead of vb2_dma_sg_plane_desc used for the manual iommu mapping).
> 
> Without an external iommu the value is overridden afterwards to 
> vb2_dma_sg_memops. I probably should move the if up to make clear that 
> this is only set for the external iommu case.
> 
> Or did I misunderstand your question?

That was it, I read quickly thinking it was always vb2_dma_contig_memops now,
regardless which iommu implementation is used. If you can make it clearer that
the ops depends on the context, that would be great.

Nicolas

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