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Wed, 25 Feb 2026 11:32:23 -0800 (PST) MIME-Version: 1.0 References: <20260225-dma-buf-heaps-as-modules-v1-0-2109225a090d@kernel.org> <20260225-dma-buf-heaps-as-modules-v1-1-2109225a090d@kernel.org> In-Reply-To: <20260225-dma-buf-heaps-as-modules-v1-1-2109225a090d@kernel.org> From: "T.J. Mercier" Date: Wed, 25 Feb 2026 11:32:11 -0800 X-Gm-Features: AaiRm50SiWoOS9CfY38Fs_M7N-g3DOx_BZCYfNv6nN_YOmBm3wEPmTfvWS_ulms Message-ID: Subject: Re: [PATCH 1/7] dma: contiguous: Turn heap registration logic around To: Maxime Ripard Cc: Sumit Semwal , Benjamin Gaignard , Brian Starkey , John Stultz , =?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-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5CB551C000F X-Stat-Signature: tuac9thqax3o6ukqpms64oz6nudgqi4k X-Rspam-User: X-HE-Tag: 1772047945-611256 X-HE-Meta: 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 Lf/nchs/ wiq2uCHrupW9swuMKkXZQsQ1fCbJUycp+K9zldnR2uLly1LDxntbBbU/9UT2bZr6ko8NyXWsFVprFP/8W/pPGLPF/kFTlvm9LSUp1lbu82w1mXD3giKp7gJAPREeGMJSMIWUZAFoZWvgUvRy54XHAzDe0yC3NX/fJwpwMvMyUM+RgcL3ZhS+/MOgOujoMQYhSyCZbQyGmUKsb9dzAce5FUdc55DdAJgAo+hKOTpwkKVRkA3T6+ow2dMO9nSWw6P0Ly0na+Z+s9Oo+VqF04wikxk2E/nSNsAMwL/ZA 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 CMA heap instantiation was initially developed by having the > contiguous DMA code call into the CMA heap to create a new instance > every time a reserved memory area is probed. > > Turning the CMA heap into a module would create a dependency of the > kernel on a module, which doesn't work. > > Let's turn the logic around and do the opposite: store all the reserved > memory CMA regions into the contiguous DMA code, and provide an iterator > for the heap to use when it probes. > > Signed-off-by: Maxime Ripard Reviewed-by: T.J. Mercier Thanks! I disabled this registration in the Android kernels where we build all dmabuf heaps as modules instead of built-in, so I can undo that if this is merged.