linux-kernel - Re: [PATCH 5.15 228/917] media: videobuf2: rework vb2_mem

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Date:   Tue, 16 Nov 2021 10:22:36 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.15 228/917] media: videobuf2: rework vb2_mem_ops API

On (21/11/15 17:55), Greg Kroah-Hartman wrote:
> From: Sergey Senozhatsky <senozhatsky@...omium.org>
> 
> [ Upstream commit a4b83deb3e76fb9385ca58e2c072a145b3a320d6 ]
> 
> With the new DMA API we need an extension of the videobuf2 API.
> Previously, videobuf2 core would set the non-coherent DMA bit
> in the vb2_queue dma_attr field (if user-space would pass a
> corresponding memory hint); the vb2 core then would pass the
> vb2_queue dma_attrs to the vb2 allocators. The vb2 allocator
> would use the queue's dma_attr and the DMA API would allocate
> either coherent or non-coherent memory.
> 
> But we cannot do this anymore, since there is no corresponding DMA
> attr flag and, hence, there is no way for the allocator to become
> aware of what type of allocation user-space has requested. So we
> need to pass more context from videobuf2 core to the allocators.
> 
> Fix this by changing the call_ptr_memop() macro to pass the
> vb2 pointer to the corresponding op callbacks.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

Hello Greg, Sasha,

This patch needs two fix up patches to be applied.

The first one is in Linus's tree (media: videobuf2: always set buffer vb2 pointer)
67f85135c57c8ea20b5417b28ae65e53dc2ec2c3

The second one isn't yet (media: videobuf2-dma-sg: Fix buf->vb NULL pointer dereference)
https://lore.kernel.org/all/20211101145355.533704-1-hdegoede@redhat.com/raw