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[169.58.107.97]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4bb55af2901sm152411795e9.13.2026.11.14.11.08.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 14 Nov 2026 11:08:37 -0800 (PST) Message-ID: <99f9a7d5-d0c7-4a86-9be2-ca0ec70c4f41@gmail.com> Date: Sat, 14 Nov 2026 22:08:34 +0300 X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: linux-bluetooth@vger.kernel.org Cc: luiz.dentz@gmail.com, kiran.k@intel.com From: Vovan Nikolaevich Subject: Hi,,,I am investigating a reproducible Bluetooth SAR initialization warning on an Intel AX201 controller in an ASUS ExpertBook B5402CBA running Gentoo Linux.,,The warning occurs during firmware initialization on both Linux 7.3.3 and 7.3.4:,,```,Bluetooth: hci0: Applying legacy Bluetooth SAR,Bluetooth: hci0: Failed to send sar ddc id:0x0137 (-22),```,,I captured the initial firmware initialization with btmon and confirmed that the controller explicitly rejects Intel DDC Config Write (0xfc8b), ID 0x0137, with HCI status 0x12.,,**Environment**,,- Hardware: Intel AX201 (USB 8087:0026),- Laptop: ASUS ExpertBook B5402CBA,- Kernel: Gentoo Linux 7.3.4-bdsm (also observed on 7.3.3-bdsm),- Bluetooth firmware: 2026.29, build 82200,- Firmware SHA1 reported by controller: 0xd3d4fa22,- CNVi TOP: 0x00080400,- CNVr TOP: 0x01300504,- Intel DDC file: intel/ibt-0040-4150.ddc (symlink to ibt-0040-0041.ddc),,**Confirmed HCI sequence**,,```,DDC ID Payload HCI status,0x0128 18 Success (0x00),0x0129 03 00 Success (0x00),0x0131 06 Success (0x00),0x0132 06 Success (0x00),0x0133 07 Success (0x00),0x0137 06 08 08 Invalid HCI Command Parameters (0x12),```,,The initial DDC configuration file contains only IDs 0x0128 and 0x0129, and both are applied successfully.,,The legacy SAR parameters come from the ACPI BRDS method at:,,```,\_SB.PC00.XHCI.RHUB.HS10,```,,The method reads the Bluetooth SAR values from the ASUS GNVS SystemMemory region. The controller initialization takes the legacy SAR path.,,In `btintel_set_legacy_sar()`, the first three SAR commands succeed. The next command, ID 0x0137 with payload `06 08 08`, is rejected. The function then returns without sending the remaining legacy SAR commands.,,**Questions**,,1. Is legacy SAR DDC ID 0x0137 with a three-byte BR/EDR payload expected to be supported by this AX201 firmware and hardware generation?,2. Are the payload values `06 08 08` valid for this command, or could the rejection indicate incompatible ACPI-provided SAR values?,3. If this rejection is expected for some Intel controllers, should `btintel` check capability or handle the unsupported command differently, while preserving the required radio power restrictions?,4. Could this result in only partial application of the platform's Bluetooth SAR settings?,,The controller finishes initialization and Bluetooth remains usable. I am not claiming that this warning causes the separate intermittent hardware error 0x0c observed on the system.,,I can provide a sanitized btmon capture, relevant DSDT/BRDS excerpts, and kernel initialization logs if useful.,,Thanks for looking into this. Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, I am investigating a reproducible Bluetooth SAR initialization warning on an Intel AX201 controller in an ASUS ExpertBook B5402CBA running Gentoo Linux. The warning occurs during firmware initialization on both Linux 7.3.3 and 7.3.4: Bluetooth: hci0: Applying legacy Bluetooth SAR Bluetooth: hci0: Failed to send sar ddc id:0x0137 (-22) I captured the initial firmware initialization with btmon and confirmed that the controller explicitly rejects Intel DDC Config Write (0xfc8b), ID 0x0137, with HCI status 0x12. Environment Hardware: Intel AX201 (USB 8087:0026) Laptop: ASUS ExpertBook B5402CBA Kernel: Gentoo Linux 7.3.4-bdsm (also observed on 7.3.3-bdsm) Bluetooth firmware: 2026.29, build 82200 Firmware SHA1 reported by controller: 0xd3d4fa22 CNVi TOP: 0x00080400 CNVr TOP: 0x01300504 Intel DDC file: intel/ibt-0040-4150.ddc (symlink to ibt-0040-0041.ddc) Confirmed HCI sequence DDC ID Payload HCI status 0x0128 18 Success (0x00) 0x0129 03 00 Success (0x00) 0x0131 06 Success (0x00) 0x0132 06 Success (0x00) 0x0133 07 Success (0x00) 0x0137 06 08 08 Invalid HCI Command Parameters (0x12) The initial DDC configuration file contains only IDs 0x0128 and 0x0129, and both are applied successfully. The legacy SAR parameters come from the ACPI BRDS method at: \_SB.PC00.XHCI.RHUB.HS10 The method reads the Bluetooth SAR values from the ASUS GNVS SystemMemory region. The controller initialization takes the legacy SAR path. In btintel_set_legacy_sar(), the first three SAR commands succeed. The next command, ID 0x0137 with payload 06 08 08, is rejected. The function then returns without sending the remaining legacy SAR commands. Questions Is legacy SAR DDC ID 0x0137 with a three-byte BR/EDR payload expected to be supported by this AX201 firmware and hardware generation? Are the payload values 06 08 08 valid for this command, or could the rejection indicate incompatible ACPI-provided SAR values? If this rejection is expected for some Intel controllers, should btintel check capability or handle the unsupported command differently, while preserving the required radio power restrictions? Could this result in only partial application of the platform's Bluetooth SAR settings? The controller finishes initialization and Bluetooth remains usable. I am not claiming that this warning causes the separate intermittent hardware error 0x0c observed on the system. I can provide a sanitized btmon capture, relevant DSDT/BRDS excerpts, and kernel initialization logs if useful. Thanks for looking into this.