boot-architecture

boot-architecture@lists.linaro.org

1 participants
679 discussions

Re: Proposal: Officially allow "incomplete" trees as a base

by Doug Anderson

Hi, On Wed, Dec 3, 2025 at 2:37 PM Doug Anderson <dianders(a)chromium.org> wrote: > > Hi, > > On Tue, Dec 2, 2025 at 3:16 PM Rob Herring <robh(a)kernel.org> wrote: > > > > > as a set of examples. I don't see a clear way to generate these from > > > a fragmented scheme. There's a similar problem with the board-level > > > compatible: > > > > > > compatible = "solidrun,cubox-i/dl", "fsl,imx6dl"; > > > compatible = "solidrun,hummingboard2/dl", "fsl,imx6dl"; > > > compatible = "solidrun,hummingboard/dl", "fsl,imx6dl"; > > > compatible = "solidrun,hummingboard2/q", "fsl,imx6q"; > > > > > > These don't include the SoM information. > > > > So we're back to needing to merge compatible even though Doug was > > willing to drop it. Or to put it another way, there's usecases for the > > base to be different SoC revisions and variants. So I don't think we > > should give up on solving that. > > I'm willing to take a crack at it. Before doing so, though, I think we > need to agree upon a definition of what the top-level "compatible" is > supposed to be. Otherwise, what exactly is our goal in trying to merge > "compatible" strings? We should have a goal of updating the official > documentation with whatever we decide. > > > I guess first, we should see what the spec says. The Devicetree > Specification v0.4 says this about the top-level compatible (which, it > should be noted, is documented _separtely_ from section 2.3.1 since > all of section 2.3 is only about device nodes): > > > Specifies a list of platform architectures with which this platform is compatible. This property can be used by operating systems in selecting platform specific code. The recommended form of the property value is: "manufacturer,model" For example: compatible = "fsl,mpc8572ds" > > That's not very detailed, but I guess we can start out looking at what > it _doesn't_ say. > > a) The spec doesn't say anything about the top-level compatible > uniquely identifying a specific hardware configuration. Nothing there > says "look at one of the strings in the list and you can tell exactly > what product you have in front of you". > > b) The spec doesn't specifically mention that one should include any > strings for a SoC / SoM / reference board. Indeed, the example given > shows an example "compatible" with just one string: "fsl,mpc8572ds". > Searching the interwebs, I find that this example "compatible" > probably refers to a Freescale "MPC8572 Development System", which is > a dev board with a "MPC8572" chip. Notably, the example "compatible" > didn't include the "MPC8572" chip. > > c) The spec doesn't seem to include a firm definition of what they > mean by the word "platform". In my mind, one could interpret the SoC > as a "platform". One could also interpret a SoM or a reference board > as a "platform". It's not necessarily clear. Since AI is the answer to > all things these days, I asked Gemini. I asked what "platform" meant > in the context of the DT spec and it (confidently) told me that "the > platform is the physical machine." ...but when I asked if one could > also consider the SoC the "platform", it told me that was "an > excellent clarifying question" and went on to say the SoC "is often > referred to as the base platform or the SoC-level platform." :-P > > > How does that help us? I guess I'd summarize that, from reading the > spec and more loosely interpreting the word "platform": > > a) The compatible string doesn't _need_ to include strings > representing the SoC, SoM, or baseboard, but it can. > > b) The compatible string is primarily there for use by the operating > system to select platform (board, reference board, SoM, or SoC) > specific code. > > > That still doesn't really tell us when we should / shouldn't include a > SoC / SoM / baseboard in the top-level "compatible". It also doesn't > tell us if we should include even more detailed levels. ...and by > "more detailed levels", I would perhaps say that each of these could > also be considered a "platform": > * google,trogdor-lazor-rev6-sku6 - An exact model of board. > * google,trogdor-lazor-rev6 - A platform that has several SKUs. > * google,trogdor-lazor - A platform that has several revisions and SKUs. > * google,trogdor - A reference platform that has several boards. > > > Perhaps we should lean into the statement "This property can be used > by operating systems in selecting platform specific code" to give us > guidance? The problem is that we somehow need to not just look at > current operating systems but, if we want to strive towards the goal > of shipping binary device trees, we need to consider future operating > system code that hasn't yet been written. That sounds impossible and > makes one think you should cram as much info into the compatible > string as possible, but... > > ...actually, we only need to put information into the compatible > string if there's not an easy way for the operating system to get the > information elsewhere, right? If the information is found elsewhere in > the device tree or if the operating system can probe the information > itself, then there's really no _need_ to put it in the top-level > "compatible" and we'll never end up painting ourselves into a corner. > We could still put the information there just to make it convenient, > but it's not really needed. Does this make sense? > > I would further argue that, in order to be useful, any given > "platform" should document its expectations and we need to be > consistent across anyone using that platform. To make it concrete, if > the Qualcomm SC7180 platform documents that "qcom,sc7180" belongs in > the top-level compatible string then all device trees including sc7180 > should have that string. This _doesn't_ mean that on some future > platform (like qcom,sc9999) we couldn't make a different decision. > Maybe on "qcom,sc9999" we've decided to put SoC details as some > properties under the "soc@0" node. Now the operating system can find > the details about which SoC is present from the "soc@0" node and > therefore we don't need to represent it in the top-level compatible > string. > > > Assuming that all makes sense, maybe the way to document the top-level > compatible string: > > -- > > Specifies a list of "platform architectures" with which this platform > is compatible. A "platform architecture" can be at any level, from the > specific board to the class of board to the reference platform to the > SoM to the SoC. A given "platform architecture" should always be > consistently included or not-included by all final device trees using > it. If the "qcom,sc7180" SoC platform is defined to be included, it > should be consistently included by any device trees with this SoC. The > criteria for whether to represent a "platform architecture" in the > top-level compatible string is the difficulty of the operating system > obtaining the information in some other way (including from other DT > properties or from probing). In general, the top-level "compatible" > used by operating systems in selecting platform specific code. The > recommended form of the property value is: "manufacturer,model" > > Examples: > > compatible = "fsl,mpc8572ds"; > - Select code related to the Freescale MPC8572 Development System > > No platform is included for the CPU since ("fsl,mpc8572") isn't > consistently listed as a platform. > > compatible = "google,snow-rev4", "google,snow", "samsung,exynos5250", > "samsung,exynos5" > - Select code related to google,snow-rev4. > - Select code related to google,snow. > - Select code related to samsung,exynos5250. > - Select code related to samsung,exynos5. > > In this example, the idea is that all exynos5 boards would have > "samsung,exynos5" so code that needed to run on "exynos5" could > consistently test for that "compatible" string. Similarly, all > exynos5250 boards would have "samsung,exynos5250" and all snow boards > would have "google,snow" > > -- > > What do folks think? > > Note that the current Chromebook stuff [1] we used on sc7180-trogdor > boards doesn't fit amazingly well into that definition, but it can > kinda squeeze in there. Essentially the sc7180-trogdor stuff is > designed around making it easy for the bootloader to find the right > device tree but doesn't provide anything terribly useful to the OS in > the top-level "compatible" string. At this point, I don't think I > would encourage others to adopt something similar. > > > If folks agree with the above interpretation, I think I'd end up back > to arguing _against_ the need to merge compatible strings. If we don't > need to put detailed SoC information into the top-level compatible > string then we don't need to merge. I think the most > flexible/futureproof would be to just define that for the SoC inside > Pixel 10 (and presumably all future Google Silicon) we'll put SoC > information under the "soc@0" node and thus there's no need to include > it in the top-level "compatible". That leaves us without a > "compatible" to put in the base "dtb", but maybe we can just put > compatible = "incomplete" or something like that? > > I suspect that even for Russell's purposes the information can either > be probed by the OS or put in places other than the top-level > compatible string. We might not want to change his existing > devicetrees in case some OS is relying on the existing compatible > strings, but for work going forward it feels like it would be a > solution... > > > [1] https://docs.kernel.org/arch/arm/google/chromebook-boot-flow.html It's me again. The pest. Adding a few people who piped up when I mentioned this at Plumbers (namely Bjorn and Geert)... Bjorn mentioned that, in general, it's hard to know what device / devicetree people are using when they report bugs. Presumably if we made the top-level compatible less representative of the overall system, this problem would be made worse? While this is true, to me it isn't necessarily a blocker (though feel free to object). Specifically: * The device tree doesn't fully describe all hardware anyway. While we might use a "SKU" variant to choose between one MIPI panel or another, Chromebooks _don't_ use SKU variants to choose between one eDP panel or another because eDP panels can be probed. We also might use a "SKU" variant to choose between two MIPI webcams but not two USB webcams for the same reason. * We've already accepted the idea of "hardware probers" that can run at boot anyway and those don't adjust SKU numbers. grep the source for "fail-needs-probe". Someone pointed out that if you really need the device tree it could be captured in bug reports. This seems reasonable to me. I also really liked the idea of keeping some sort of log somewhere in the device tree every time an overlay is applied, though I tend to agree with others that filenames of device tree files shouldn't be ABI. Geert talked about the top-level compatible as being the "last resort" to fix any issue. That matches my understanding above from reading the docs and seeing how it was used. Geert: I would be curious what you thought about my arguments above. In general, I'm still hoping to figure out next steps. I believe this problem is important enough that we shouldn't just drop it due to silence, so I'll continue being my usual noisy self and keep pestering. -Doug

3 months, 1 week

No EBBR call today Dec 3?

by Vincent Stehlé

Dear EBBR stakeholders, We have currently no agenda for today's EBBR call. [1] If you have a topic to discuss today, please let us know before 11am UTC, otherwise we will adjourn the call. Best regards, Vincent Stehlé System Architect - Arm [1] https://github.com/ARM-software/ebbr/wiki/EBBR-Meetings

3 months, 2 weeks

Proposal: Officially allow "incomplete" trees as a base

by Doug Anderson

This is a continuation of the discussion that started in reply to my patch adding basic device trees for Pixel 10 phones [1]. Problem statement: ------------------ We would like an officially accepted scheme that lets us more efficiently ship compiled device trees for a handful of related products by breaking the device trees up into a common "base" device tree and then applying "overlay" device trees atop the base to make a full and complete device tree. To make it more concrete, we'd like to build a "base" device tree that describes a SoC and then have the overlays be enough to make a full description of a board. In theory, one could also imagine wanting to expand this to 3 or more levels (perhaps SoC, baseboard, derived boards), though this is not planned at this time. The primary reason for wanting to break device trees like this is efficiency of the shipped binary device trees. A large portion of a final device tree just describes the SoC. We save space in the final compiled device trees if they don't need to contain as much duplicated information. A secondary reason for wanting to break device trees like this is to more nicely handle when a board has a socketed SoC that can be replaced with a finite (and small) number of different SoCs (usually revisions of the same SoC). Even if this secondary reason is considered invalid or too difficult, the primary reason still describes a compelling need. In order to make this proposal work, it's expected that a bootloader will understand the scheme and will know how to combine the overlay atop the base before passing a complete device tree to the main OS. Current state of the art (downstream): -------------------------------------- In Android, we do a pretty good job of solving the stated problem using device tree overlays. We describe the SoCs in "dts" files and compile them into "dtb"s. We describe boards in "dtso" files and compile them into "dtbo" files. A bootloader can handle identifying the correct base and overlay (the scheme for doing this is a separate but related topic) and applying the overlay atop the base "dtb". This solution is fully implemented downstream for Android phones and is well documented [2]. The issues I'm aware of with the current state of the art are: 1. In order for the base device tree to pass schema validation on its own we'd need to document the top-level compatible strings in the device tree. It is the opinion of at least some device tree maintainers that a SoC doesn't qualify as a top-level compatible string. This prevents the device trees from landing in an officially sanctioned location. 2. It is also possible we may fail schema validation for the base SoC tree if the schema marks a property as "required" but that property needs to be filled out by the board (perhaps a "-supply" is marked as "required", since most "-supply" properties are filled in by the board. I'm not sure this is a big issue, but it's something to think about. 3. It's unclear if there is any official "ABI" promised here once we've compiled and validated the base device tree on its own. Will people assume that they can have out-of-tree overlays derived from the base SoC tree and that those out-of-tree overlays will continue to work across changes / cleanups to the base? NOTE: this is a pre-existing question for existing device tree overlay usage, but the sheer quantity of nodes/properties that a board would be expected to overlay/modify in the base make the problem more prominent. 4. We want the final device tree's top-level compatible to be all the compatible strings from the board followed by all of the compatible strings for the SoC. When the board's overlay is applied to the base SoC tree, though, the board's top-level compatible fully replaces the compatible from the base SoC tree. This can be solved today for non-socketed boards by just duplicating the SoC compatible strings in the board overlays. We can't solve this today for socketed boards, though we can simply make sure that no software drivers rely on the specific SoC compatible string being present and thus we can ignore the problem. None of the above problems are big enough to have prevented widespread use of this scheme in downstream Android. Current state of the art (upstream): ------------------------------------ Upstream if we have a pile of related boards, we do allow deduplicating things at a source-code level with "dtsi" files. We can have a SoC "dtsi" file and that file is included by all boards that use that SoC. When it comes time to validate or ship things, though, we only work with full devices trees. This means that we ship duplicated information. Proposal: --------- 1. Allow the top-level compatible string of an "incomplete" device tree to be documented so it can be validated on its own by tools. It's understood that this SoC is not a board by itself and we'd never boot a full OS with this device tree without adding an overlay that changes the top-level compatible. Add a top-level property to the device tree (perhaps "incomplete-compatible;") to indicate that the tree is not complete without an overlay. 2. If it turns out to be needed (hopefully it's not), allow some type of syntax in yaml files that allows a property to be marked as "required" in a "complete" device tree but not in an "incomplete" device tree. Alternatively, we could discourage marking properties as "required" if they're expected to be filled in by a board. 3. Define that there is no promised ABI between "incomplete" device trees and anything not stored with them. Specifically, all valid combinations of "incomplete" device trees with overlays to complete them should be enumerated together with the "incomplete" device tree. 4. When applying an overlay to a device tree that's "incomplete", the top level overlay will be merged instead of replaced. Example for 2 levels: base (incomplete) compatible: "socvendor,mysoc-rev1", "socvendor,mysoc"; overlay compatible: "boardvendor,myboard-rev1", "boardvendor,myboard"; merged compatible: "boardvendor,myboard-rev1", "boardvendor,myboard", "socvendor,mysoc-rev1", "socvendor,mysoc"; Possible example if we support 3 levels: SoC (incomplete) compatible: "socvendor,mysoc-rev1", "socvendor,mysoc" overlay1 (incomplete) compatible: "referencevendor,referencecodename"; overlay2 compatible: "boardvendor,myboard-rev1", "boardvendor,myboard" merged compatible: "boardvendor,myboard-rev1", "boardvendor,myboard", "referencevendor,reference-codename", "socvendor,mysoc-rev1", "socvendor,mysoc"; Obviously in the 3-level scheme we need to know the order that overlays are applied, but that's true for overlays today anyway. The above proposal takes the current downstream "state of the art" and addresses the known issues, solving the original problem statement. Other thoughts: --------------- If you don't like the proposal, I'd be interested in knowing if you have other ideas for solving the original problem statement, or if you simply think the problem we're trying to solve here is an invalid one. I'm happy to post up another revision of my Pixel 10 device trees following this proof of concept (or other ones). My v1 was _very_ close to this, but didn't have the "incomplete-compatible;" property and didn't implement top-level compatible merging. [1] https://lore.kernel.org/r/20251111112158.1.I72a0b72562b85d02fee424fed939fea… [2] https://source.android.com/docs/core/architecture/dto/partitions

3 months, 2 weeks

EBBR call today Nov 19

by Vincent Stehle

(This is a resend; sorry if you receive this e-mail twice.) Dear EBBR contributors, We will have our EBBR call today, Nov 19 at 14:00 UTC. [1] We have four pull requests on the agenda [2]: - Pull request #151: references: update RISC-V references - Pull request #152: Recommend firmware TRNG - Pull request #153: Add a note on SMCCC conduits - Pull request #154: Recommend the SOC_ID SMCCC call We will use this pad [3] for the meeting notes. Feel free to add topics to the agenda, directly on the wiki page, by e-mail or on the pad. Best regards, Vincent Stehlé System Architect - Arm [1] https://armltd.zoom.us/j/92081365511?pwd=SFZpRitXUEp3Zy9GM0h3UUZ1b1pnUT09 [2] https://github.com/ARM-software/ebbr/wiki/EBBR-Meetings [3] https://mensuel.framapad.org/p/ebbr-call-of-nov-19-ahzj?lang=en #151: https://github.com/ARM-software/ebbr/pull/151 #152: https://github.com/ARM-software/ebbr/pull/152 #153: https://github.com/ARM-software/ebbr/pull/153 #154: https://github.com/ARM-software/ebbr/pull/154 IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.

4 months

EBBR call today Nov 19

by Vincent Stehlé

Dear EBBR contributors, We will have our EBBR call today, Nov 19 at 14:00 UTC. [1] We have four pull requests on the agenda [2]: - Pull request #151: references: update RISC-V references - Pull request #152: Recommend firmware TRNG - Pull request #153: Add a note on SMCCC conduits - Pull request #154: Recommend the SOC_ID SMCCC call We will use this pad [3] for the meeting notes. Feel free to add topics to the agenda, directly on the wiki page, by e-mail or on the pad. Best regards, Vincent Stehlé System Architect - Arm [1] https://armltd.zoom.us/j/92081365511?pwd=SFZpRitXUEp3Zy9GM0h3UUZ1b1pnUT09 [2] https://github.com/ARM-software/ebbr/wiki/EBBR-Meetings [3] https://mensuel.framapad.org/p/ebbr-call-of-nov-19-ahzj?lang=en #151: https://github.com/ARM-software/ebbr/pull/151 #152: https://github.com/ARM-software/ebbr/pull/152 #153: https://github.com/ARM-software/ebbr/pull/153 #154: https://github.com/ARM-software/ebbr/pull/154

4 months

EBBR call today Nov 5

by Vincent Stehlé

Dear EBBR contributors, We will have our EBBR call today, Nov 5 at 14:00 UTC. [1] Note: BST is not observed anymore. The call will begin at 14:00 UTC. We have four pull requests on the agenda [2]: - Pull request #142: SCMI requirements - Pull request #148: Fix bibliography alignment for PDF and HTML - Pull request #149: chapter1: do not mention levels - Pull request #150: Clarify compatibility We will use this pad [3] for the meeting notes. Feel free to add to the agenda, directly on the wiki page, by e-mail or on the pad. Best regards, Vincent Stehlé System Architect - Arm [1] https://armltd.zoom.us/j/92081365511?pwd=SFZpRitXUEp3Zy9GM0h3UUZ1b1pnUT09 [2] https://github.com/ARM-software/ebbr/wiki/EBBR-Meetings [3] https://mensuel.framapad.org/p/ebbr-call-of-nov-5-ahq7?lang=en #142: https://github.com/ARM-software/ebbr/pull/142 #148: https://github.com/ARM-software/ebbr/pull/148 #149: https://github.com/ARM-software/ebbr/pull/149 #150: https://github.com/ARM-software/ebbr/pull/150

4 months, 2 weeks

SMBIOS discovery for DT platforms booting without EFI

by Ard Biesheuvel

L.S., Adriana is proposing [0] a method for DT based platforms that boot without EFI to expose the SMBIOS tables via the /chosen DT node. There appears to be consensus between the stakeholders in the u-boot and linux communities that this is a reasonable thing to do, and it looks like this is going to be adopted soon. Adriana has kindly agreed to contributing the u-boot side implementation as well, so all the pieces will be there in terms of code. What is lacking is a contribution to the DMTF spec, which currently only permits the EFI config table method for non-x86 systems. So some wording should be added to paragraph 5.2.2 (SMBIOS 3.9 [1]) It currently reads On non-UEFI systems, the 64-bit SMBIOS Entry Point structure can be located by application software by searching for the anchor-string on paragraph (16-byte) boundaries within the physical memory address range 000F0000h to 000FFFFFh. Given that this makes sense only on x86 systems, I suggest we rephrase this along the lines of On non-UEFI systems, the 64-bit SMBIOS Entry Point structure can be located by application software - on x86 systems only, by searching for the anchor-string on paragraph (16-byte) boundaries within the physical memory address range 000F0000h to 000FFFFFh, - on DT based systems, by obtaining the physical memory address of the structure from the /chosen/smbios3-entrypoint property in the device tree. Maybe Rob can suggest a normative reference to be added to section 2? Thanks, Ard. [0] https://lore.kernel.org/all/CAERbo5z6BzHqQxXdxPxmxE_eDR7GGGbt3A8kB0gQiWFBE-… [1] https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.9.0.…

4 months, 2 weeks

Re: [PATCH v4 1/2] dt-bindings: firmware: Add binding for SMBIOS /chosen properties

by Rob Herring

On Fri, Oct 31, 2025 at 5:10 AM adriana <adriana(a)arista.com> wrote: > > Signed-off-by: adriana <adriana(a)arista.com> > --- > .../firmware/linux,smbios3-entrypoint.yaml | 25 +++++++++++++++++++ > 1 file changed, 25 insertions(+) > create mode 100644 Documentation/devicetree/bindings/firmware/linux,smbios3-entrypoint.yaml > > diff --git a/Documentation/devicetree/bindings/firmware/linux,smbios3-entrypoint.yaml b/Documentation/devicetree/bindings/firmware/linux,smbios3-entrypoint.yaml > new file mode 100644 > index 000000000000..4d1521c685ff > --- /dev/null > +++ b/Documentation/devicetree/bindings/firmware/linux,smbios3-entrypoint.yaml > @@ -0,0 +1,25 @@ > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > +# Copyright 2025 Arista Networks > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/firmware/linux,smbios3-entrypoint.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: Memory location for SMBIOS entry point > + > +description: | > + This property is used in the /chosen node to pass the physical address > + of SMBIOS (System Management BIOS) or DMI (Desktop Management Interface) > + tables from firmware to the kernel. This is typically used on non-EFI. > + > +maintainers: > + - Adriana Nicolae <adriana(a)arista.com> > + - Rob Herring <robh+dt(a)kernel.org> > + > +properties: > + linux,smbios3-entrypoint: > + $ref: /schemas/types.yaml#/definitions/uint64 > + description: > + The 64-bit physical address of the SMBIOSv3 entry point structure. This needs to go in the chosen binding instead: https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/chos…

4 months, 3 weeks

Re: [PATCH v4 0/2] DMI: Scan for DMI table from DTS info

by Ard Biesheuvel

On Fri, 31 Oct 2025 at 11:10, adriana <adriana(a)arista.com> wrote: > > Some bootloaders like U-boot, particularly for the ARM architecture, > provide SMBIOS/DMI tables at a specific memory address. However, these > systems often do not boot using a full UEFI environment, which means the > kernel's standard EFI DMI scanner cannot find these tables. > > This series adds support for the kernel to find these tables by > reading the associated property from the Device Tree /chosen node. The > bootloader can specify the physical addresses using the property > "linux,smbios3-entrypoint". > > The first patch introduces the device tree binding documentation for this > new ABI, and the second patch implements the driver logic in dmi_scan.c. > > Changes in v4: > - Renamed linux,smbios3-table.yaml file, removed mention of ARM/ARM64 > (Patch 1/2). > - Drop the second definition of dmi_scan_from_dt() and fold checking > for CONFIG_OF (Patch 2/2). > - Drop unnecessary goto on the success case (Patch 2/2). > - Replace magic number for entrypoint size with SMBIOS3_ENTRY_POINT_SIZE > definition (Patch 2/2). > > Changes in v3: > - Removed linux,smbios-table property, only keep the SMBIOSv3 property > (Patch 1/2). > - Search DT for linux,smbios3-table only, removed the code searching > for the previous property (Patch 2/2). > > Changes in v2: > - Add missing Device Tree binding documentation (Patch 1/2). > - Split the original patch into a 2-part series (binding + driver). > - (No functional changes to the driver code in patch 2/2). > > adriana (2): > dt-bindings: firmware: Add binding for SMBIOS /chosen properties > drivers: firmware: dmi_scan: Add support for reading SMBIOS from DT > For the series, Reviewed-by: Ard Biesheuvel <ardb(a)kernel.org> I can take the second patch, but bindings need to go in separately IIRC. Rob? > .../firmware/linux,smbios3-entrypoint.yaml | 25 +++++++++ > drivers/firmware/dmi_scan.c | 54 +++++++++++++++++++ > 2 files changed, 79 insertions(+) > create mode 100644 Documentation/devicetree/bindings/firmware/linux,smbios3-entrypoint.yaml > > -- > 2.51.0 >

4 months, 3 weeks

Re: [PATCH v3 2/2] drivers: firmware: dmi_scan: Add support for reading SMBIOS from DT

by Ilias Apalodimas

Hi Adriana, On Fri, 31 Oct 2025 at 10:41, adriana <adriana(a)arista.com> wrote: > > From: Adriana Nicolae <adriana(a)arista.com> We'll need a description of why the change is needed here. [...] > > #ifndef SMBIOS_ENTRY_POINT_SCAN_START > #define SMBIOS_ENTRY_POINT_SCAN_START 0xF0000 > @@ -670,6 +673,54 @@ static int __init dmi_smbios3_present(const u8 *buf) > return 1; > } > > +#if IS_ENABLED(CONFIG_OF) > +/** > + * dmi_scan_from_dt - Find and parse DMI/SMBIOS tables from the Device Tree > + * > + * Checks if the bootloader has passed SMBIOS table addresses via the /chosen > + * node in the Device Tree. This follows the standard kernel DT bindings and > + * assumes a fixed 32-byte mapping for the entry point. > + * Returns true if a valid table is found and successfully parsed. > + */ > +static bool __init dmi_scan_from_dt(void) > +{ > + struct device_node *chosen; > + const __be64 *prop; > + char buf[32]; > + void __iomem *p; > + bool dmi_available = false; > + u64 addr; > + int len; > + > + chosen = of_find_node_by_path("/chosen"); > + if (!chosen) > + return false; > + > + prop = of_get_property(chosen, "linux,smbios3-table", &len); > + if (prop && len >= sizeof(u64)) { > + addr = be64_to_cpup(prop); > + > + p = dmi_early_remap(addr, 32); Please put '32' into a define that explains what it is > + if (p == NULL) I think if (!p) is preferred > + goto out; > + > + memcpy_fromio(buf, p, sizeof(buf)); > + dmi_early_unmap(p, 32); > + > + if (!dmi_smbios3_present(buf)) { > + dmi_available = true; > + goto out; > + } > + } > + > +out: > + of_node_put(chosen); > + return dmi_available; > +} > +#else > +static bool __init dmi_scan_from_dt(void) { return false; } > +#endif /* IS_ENABLED(CONFIG_OF) */ > + > static void __init dmi_scan_machine(void) > { > char __iomem *p, *q; > @@ -718,6 +769,13 @@ static void __init dmi_scan_machine(void) > dmi_available = 1; > return; > } > + } else if (IS_ENABLED(CONFIG_OF) && dmi_scan_from_dt()) { Can you fold the IS_ENABLED() in dmi_scan_from_dt() please? > + /* [...] Thanks /Ilias

4 months, 3 weeks

Jump to page:

2026

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

boot-architecture