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Wed, 25 Feb 2026 10:51:42 -0800 (PST) MIME-Version: 1.0 References: <20260225-dma-buf-heaps-as-modules-v1-0-2109225a090d@kernel.org> In-Reply-To: <20260225-dma-buf-heaps-as-modules-v1-0-2109225a090d@kernel.org> From: John Stultz Date: Wed, 25 Feb 2026 10:51:30 -0800 X-Gm-Features: AaiRm510JicR5yB6-6HzIZrjZoL6Jbi8o9bjBsqrkrZBCAWaavoCU9peMfkjjyM Message-ID: Subject: Re: [PATCH 0/7] dma-buf: heaps: Turn heaps into modules To: Maxime Ripard Cc: Sumit Semwal , Benjamin Gaignard , Brian Starkey , "T.J. Mercier" , =?UTF-8?Q?Christian_K=C3=B6nig?= , Marek Szyprowski , Robin Murphy , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: diwyzyfo6mdar4oskr5g3kgnyzmfmsba X-Rspam-User: X-Rspamd-Queue-Id: C47971C0008 X-Rspamd-Server: rspam01 X-HE-Tag: 1772045504-313645 X-HE-Meta: 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 QkElyU/T sLYVj5TX8eamDfakC6Kn68qh/DWHF48KLjcYKdUwgZfUuo2fXf5qm7JVGuAoB9XVeKRgXHL3N1HSh+eGolmPekCf7AVPri03KfqYiK2XMNftaFwijegqhW0lpsybcE2MFhU+p/ZsQObz3Gyja3LUGMbXZTT6lJ7iZsgIUAhhDozbcJGfJ/o4TyoBL9goP+thhJwNBoYUilgiR9ko6YgW94TL/9oLh6HnI2GZK82v1PgHo3QN99ZAxOL9ggmV936S/wNMiZcdAZPKWOL+Y00s60i27b8aNnM+D7d02mTHl0PLHAJ+OtsUBz4XHovjIOJ4nVAOZ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 25, 2026 at 8:42=E2=80=AFAM Maxime Ripard = wrote: > > The recent introduction of heaps in the optee driver [1] made possible > the creation of heaps as modules. > > It's generally a good idea if possible, including for the already > existing system and CMA heaps. > > The system one is pretty trivial, the CMA one is a bit more involved, > especially since we have a call from kernel/dma/contiguous.c to the CMA > heap code. This was solved by turning the logic around and making the > CMA heap call into the contiguous DMA code. > So heaps-as-modules is common in the Android kernels, and was attempted to be upstreamed long ago: https://lore.kernel.org/lkml/20191025234834.28214-1-john.stultz@linaro.or= g/ And it got a fairly chilly reception, but maybe having the additional optee heap (as well as other proposed heaps) might sway folks on this now. There is also the kref bits you might need (which Android still carries): https://lore.kernel.org/lkml/20200725032633.125006-1-john.stultz@linaro.o= rg/ thanks -john