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Date: Fri, 23 Feb 2024 07:37:23 +0100
From: Christoph Hellwig <hch@lst.de>
To: Howard Yen <howardyen@google.com>
Cc: Christoph Hellwig <hch@lst.de>, m.szyprowski@samsung.com,
	robin.murphy@arm.com, gregkh@linuxfoundation.org,
	andriy.shevchenko@linux.intel.com, rafael@kernel.org,
	broonie@kernel.org, james@equiv.tech, james.clark@arm.com,
	masahiroy@kernel.org, linux-kernel@vger.kernel.org,
	iommu@lists.linux.dev
Subject: Re: [PATCH v3] dma-coherent: add support for multi coherent rmems
 per dev
Message-ID: <20240223063723.GB11004@lst.de>
References: <20240208152808.3712149-1-howardyen@google.com> <20240213055426.GA22451@lst.de> <CAJDAHvZGnzKPLaovRcq_Os1Fcixp2o1kY9GFV8VXztrmKahejQ@mail.gmail.com> <20240220055241.GA7554@lst.de> <CAJDAHvbOnAvW5f6oJUnuy2_5-vS7uJc13GQSNX_Nc25GJXSp-Q@mail.gmail.com>
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On Wed, Feb 21, 2024 at 05:27:58PM +0800, Howard Yen wrote:
> The reason why I tried to propose this patch is that in the system I'm
> working on, where the driver utilizes the coherent reserved memory in
> the subsystem for DMA, which has limited memory space as its primary
> usage. During the execution of the driver, there is a possibility of
> encountering memory depletion scenarios with the primary one.
> 
> To address this issue, I tried to create a patch that enables the
> coherent reserved memory driver to support multiple coherent reserved
> memory regions per device. This modification aims to provide the
> driver with the ability to search for memory from a secondary region
> if the primary memory is exhausted, and so on.

This all seems pretty vague.  Can you point to your driver submission
and explain why it can't just use a larger region instead of multiple
smaller ones?