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[84.135.187.212]) by smtp.gmail.com with ESMTPSA id s12sm957672wmh.34.2019.07.01.18.25.52 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jul 2019 18:25:53 -0700 (PDT) Subject: Re: [PATCH v2 1/2] platform: Fix device check for surfacepro3_button To: Yu Chen Cc: linux-kernel@vger.kernel.org, linux-input@vger.kernel.org, platform-driver-x86@vger.kernel.org, Dmitry Torokhov , Hans de Goede , Darren Hart , Andy Shevchenko , Benjamin Tissoires References: <20190702003740.75970-1-luzmaximilian@gmail.com> <20190702003740.75970-2-luzmaximilian@gmail.com> <20190702011443.GA19902@chenyu-office.sh.intel.com> From: Maximilian Luz Message-ID: <91349d00-e7e2-887b-45e5-4689a401aa2f@gmail.com> Date: Tue, 2 Jul 2019 03:25:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190702011443.GA19902@chenyu-office.sh.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/2/19 3:14 AM, Yu Chen wrote: > On Tue, Jul 02, 2019 at 02:37:39AM +0200, Maximilian Luz wrote: >> +/* >> + * Surface Pro 4 and Surface Book 2 / Surface Pro 2017 use the same device >> + * ID (MSHW0040) for the power/volume buttons. Make sure this is the right >> + * device by checking for the _DSM method and OEM Platform Revision. >> + */ >> +static int surface_button_check_MSHW0040(struct acpi_device *dev) >> +{ >> + acpi_handle handle = dev->handle; >> + union acpi_object *result; >> + u64 oem_platform_rev = 0; >> + >> + // get OEM platform revision >> + result = acpi_evaluate_dsm_typed(handle, &MSHW0040_DSM_UUID, >> + MSHW0040_DSM_REVISION, >> + MSHW0040_DSM_GET_OMPR, >> + NULL, ACPI_TYPE_INTEGER); >> + > Does it mean, only 5th, 6th and newer platforms have OEM platform revision? > 3rd/4th will get NULL result? Or the opposite? Correct, from my testing (with limited sample size) and AML code: 5th and 6th generation devices have a non-zero OEM platform revision, whereas 3rd and 4th gen. devices do not have any (i.e. result will be NULL). >> + if (result) { >> + oem_platform_rev = result->integer.value; >> + ACPI_FREE(result); >> + } >> + >> + dev_dbg(&dev->dev, "OEM Platform Revision %llu\n", oem_platform_rev); >> + >> + return oem_platform_rev == 0 ? 0 : -ENODEV; > if 3rd/4th do not have this oem rev information while 5th/newer have, > why the latter returns NODEV(it actually has this info)? Since we always expect a non-zero platform revision (for 5th/6th gen.), we can initialize it to zero and use that as "unknown"/"not available". So if it can not be determined, we return NODEV. >> +} Cheers, Maximilian