From f4cdf7ca9a1fdcca413157df19753f388a5a224e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Aug 2026 10:09:22 -0700 Subject: Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ... --- Documentation/userspace-api/dma-buf-heaps.rst | 74 +++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 Documentation/userspace-api/dma-buf-heaps.rst (limited to 'Documentation/userspace-api/dma-buf-heaps.rst') diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst new file mode 100644 index 000000000..f56b743cd --- /dev/null +++ b/Documentation/userspace-api/dma-buf-heaps.rst @@ -0,0 +1,74 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================== +Allocating dma-buf using heaps +============================== + +Dma-buf Heaps are a way for userspace to allocate dma-buf objects. They are +typically used to allocate buffers from a specific allocation pool, or to share +buffers across frameworks. + +Heaps +===== + +A heap represents a specific allocator. The Linux kernel currently supports the +following heaps: + + - The ``system`` heap allocates virtually contiguous, cacheable, buffers. + + - The ``system_cc_shared`` heap allocates virtually contiguous, cacheable, + buffers using shared (decrypted) memory. It is only present on + confidential computing (CoCo) VMs where memory encryption is active + (e.g., AMD SEV, Intel TDX). The allocated pages have the encryption + bit cleared, making them accessible for device DMA without TDISP + support. On non-CoCo VM configurations, this heap is not registered. + + - The ``default_cma_region`` heap allocates physically contiguous, + cacheable, buffers. Only present if a CMA region is present. Such a + region is usually created either through the kernel commandline + through the ``cma`` parameter, a memory region Device-Tree node with + the ``linux,cma-default`` property set, or through the + ``CMA_SIZE_MBYTES`` or ``CMA_SIZE_PERCENTAGE`` Kconfig options. Prior + to Linux 6.17, its name wasn't stable and could be called + ``reserved``, ``linux,cma``, or ``default-pool``, depending on the + platform. + + - A heap will be created for each reusable region in the device tree + with the ``shared-dma-pool`` compatible, using the full device tree + node name as its name. The buffer semantics are identical to + ``default-cma-region``. + +Naming Convention +================= + +``dma-buf`` heaps name should meet a number of constraints: + +- The name must be stable, and must not change from one version to the other. + Userspace identifies heaps by their name, so if the names ever change, we + would be likely to introduce regressions. + +- The name must describe the memory region the heap will allocate from, and + must uniquely identify it in a given platform. Since userspace applications + use the heap name as the discriminant, it must be able to tell which heap it + wants to use reliably if there's multiple heaps. + +- The name must not mention implementation details, such as the allocator. The + heap driver will change over time, and implementation details when it was + introduced might not be relevant in the future. + +- The name should describe properties of the buffers that would be allocated. + Doing so will make heap identification easier for userspace. Such properties + are: + + - ``contiguous`` for physically contiguous buffers; + + - ``protected`` for encrypted buffers not accessible the OS; + +- The name may describe intended usage. Doing so will make heap identification + easier for userspace applications and users. + +For example, assuming a platform with a reserved memory region located +at the RAM address 0x42000000, intended to allocate video framebuffers, +physically contiguous, and backed by the CMA kernel allocator, good +names would be ``memory@42000000-contiguous`` or ``video@42000000``, but +``cma-video`` wouldn't. -- cgit v1.3.1