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Wed, 22 Oct 2025 04:45:39 -0700 (PDT) From: adriana To: krzk@kernel.org, robh+dt@kernel.org, jdelvare@suse.com, frowand.list@gmail.com Cc: linux-arm-kernel@lists.infradread.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, vasilykh@arista.com, adriana@arista.com Subject: [PATCH v2 2/2] drivers: firmware: dmi_scan: Add support for reading SMBIOS from DT Date: Wed, 22 Oct 2025 04:45:27 -0700 Message-ID: <20251022114527.618908-3-adriana@arista.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251022114527.618908-1-adriana@arista.com> References: <0f006338-e69b-4b3f-b91f-0cc683544011@kernel.org> <20251022114527.618908-1-adriana@arista.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Signed-off-by: adriana --- drivers/firmware/dmi_scan.c | 74 +++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c index 70d39adf50dc..ea3ed40d0370 100644 --- a/drivers/firmware/dmi_scan.c +++ b/drivers/firmware/dmi_scan.c @@ -10,6 +10,9 @@ #include #include #include +#if IS_ENABLED(CONFIG_OF) +#include +#endif =20 #ifndef SMBIOS_ENTRY_POINT_SCAN_START #define SMBIOS_ENTRY_POINT_SCAN_START 0xF0000 @@ -670,6 +673,70 @@ static int __init dmi_smbios3_present(const u8 *buf) return 1; } =20 +#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 /cho= sen + * node in the Device Tree. This follows the standard kernel DT bindings a= nd + * 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 =3D false; + u64 addr; + int len; + + chosen =3D of_find_node_by_path("/chosen"); + if (!chosen) + return false; + + /* SMBIOSv3 (64-bit entry point) has priority */ + prop =3D of_get_property(chosen, "linux,smbios3-table", &len); + if (prop && len >=3D sizeof(u64)) { + addr =3D be64_to_cpup(prop); + + p =3D dmi_early_remap(addr, 32); + if (p =3D=3D NULL) + goto out; + + memcpy_fromio(buf, p, sizeof(buf)); + dmi_early_unmap(p, 32); + + if (!dmi_smbios3_present(buf)) { + dmi_available =3D true; + goto out; + } + } + + prop =3D of_get_property(chosen, "linux,smbios-table", &len); + if (prop && len >=3D sizeof(u64)) { + addr =3D be64_to_cpup(prop); + + p =3D dmi_early_remap(addr, 32); + if (p =3D=3D NULL) + goto out; + + memcpy_fromio(buf, p, sizeof(buf)); + dmi_early_unmap(p, 32); + + if (!dmi_present(buf)) + dmi_available =3D true; + } + +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 +785,13 @@ static void __init dmi_scan_machine(void) dmi_available =3D 1; return; } + } else if (IS_ENABLED(CONFIG_OF) && dmi_scan_from_dt()) { + /* + * If EFI is not present or failed, try getting SMBIOS + * tables from the Device Tree. + */ + dmi_available =3D 1; + return; } else if (IS_ENABLED(CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK)) { p =3D dmi_early_remap(SMBIOS_ENTRY_POINT_SCAN_START, 0x10000); if (p =3D=3D NULL) --=20 2.51.0