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Mon, 31 Aug 2026 00:54:02 -0700 (PDT) From: Aditya To: Derek John Clark Cc: Ilpo =?utf-8?q?J=C3=A4rvinen?= , Armin Wolf , Hans de Goede , Mark Pearson , Guenter Roeck , Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, platform-driver-x86@vger.kernel.org Subject: Re: [RFC PATCH 3/3] platform/x86: lenovo: Add Legion Go Fan Method curve driver Date: Mon, 31 Aug 2026 12:55:03 +0530 Message-Id: <53842308-7AA5-4885-94D9-527F6140CA6C@gmail.com> In-Reply-To: References: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Hi Derek, Thanks for the review. I have been investigating the BIOS of a sample of devices, which can be broadly classified as follows: - Do not have Fan Method - 8JCN - Legion Y530-15ICH - BHCN - Legion Y540, Y545, and Y7000 2019 families - Have Fan Method - Do not have Method 5 / stub - K1CN - Legion 7 16IAX7, Legion Y9000K IAX7 - JVCN - Yoga Slim 7 ProX 14ARH7 - Have Method 5 - Take direct input for Method 6 - All Legion Go, Go 2, Go S (N3CN, RRCN, RQCN, QCCN, S0CN) - Take index based input for Method 6 - Have Method 5 SensorTable equal to Method 5 FanTable - M3CN - Legion Slim 5 16APH8, 16ARH8 - LYCN - LOQ 15APH8, 16APH8 - R3CN - LOQ 15IRX10, 17IRX10; G5000 IRX10 - R8CN - LOQ 15AHP10 - Have Method 5 SensorTable be all zeros - N2CN - Legion Pro 7 16IRX9H; Legion Y9000P IRX9H - LPCN - Legion Pro 5 16ARX8, Pro 7 16ARX8H, R9000P ARX8 variants - KWCN - Legion Pro 5 16IRX8, Pro 7 16IRX8/16IRX8H, Y9000P IRX8 variants - MHCN - Legion 9 16IRX8 - RYCN - Legion 5 15AKP10; R7000 AKP10 - Q8CN - LOQ 15IAX9E - Q7CN - Legion Pro 7 16IAX10H; Y9000P IAX10 - RZCN - Legion 9 18IAX10; Legion NX IAX10 - RGCN - Legion 5 15AHP10; R7000 AHP10 - RECN - Legion Pro 5 16AFR10; R7000P/R9000P AFR10 variants For the direct based families, there is no actual discriminator or value that can tell that the devices take direct input. There are two possible discriminators I have found so far: - SensorTable contains 10, 20, 30, ..., 100 exactly - Their Fan Table GUID read function is a stub - However the Legion Go 1 does not conform to this, therefore it has to become a quirk. None of the direct based families expose any information on the range of each point on the curve. 0-100 can be taken as the nominal range. For the index based families, Legion drivers send the current power tier (current_mode) as the first Method 6 byte. However, this value comes from the Other Mode GUID. All families can use FanTableSize and SensorTableSize for their respective Method 5 arrays. FanTableSize can be used for the Method 6 array size. Then, based on this power tier, the respective Fan Table GUID table is accessed. FanTable_Len for that table determines the range of each point for Method 6. Each index will be within 1..FanTable_Len. None of the reviewed Method 6 implementations consume SensorTable values. The driver should not read back Method 6. Consumers can use Method 5 if they need to confirm the result. The Other Mode GUID for these families did not seem to have a fan table route through it. Only Full Speed and individual fan speed controls were found here. The firmware based fan curve remains under Fan Method 5/6. Regarding individual fan speed controls, they did not work on my Legion Go 1 device. Submitting RPM to it does not change the RPM. The EC fields which take this input are not exposed to any WMI interface as far as I have seen on the Legion Go 1. This also cannot replace firmware based fan curves as it will require a userspace driver to continuously monitor temperature and set RPM. Some open questions: - How should the Other Mode dependency be resolved? Should it be a helper in Fan Method, or should Fan Method be incorporated directly? - What should be the discriminator for direct based families? Thanks, Aditya