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([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-724de532db3sm8547081b3a.93.2024.11.26.08.19.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Nov 2024 08:19:53 -0800 (PST) Sender: Guenter Roeck Message-ID: <77fce1aa-96eb-4c3c-ab0a-a33de46b333b@roeck-us.net> Date: Tue, 26 Nov 2024 08:19:52 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/4] hwmon: (acpi_power_meter) Fix using uninitialized variables To: "lihuisong (C)" , linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Cc: jdelvare@suse.com, liuyonglong@huawei.com, zhanjie9@hisilicon.com, zhenglifeng1@huawei.com References: <20241125093415.21719-1-lihuisong@huawei.com> <20241125093415.21719-2-lihuisong@huawei.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/25/24 23:03, lihuisong (C) wrote: > > 在 2024/11/26 12:04, Guenter Roeck 写道: >> On 11/25/24 17:56, lihuisong (C) wrote: >>> Hi Guente, >>> >>> Thanks for your timely review. >>> >>> 在 2024/11/26 0:03, Guenter Roeck 写道: >>>> On 11/25/24 01:34, Huisong Li wrote: >>>>> The 'power1_alarm' attribute uses the 'power' and 'cap' in the >>>>> acpi_power_meter_resource structure. However, these two fields are just >>>>> updated when user query 'power' and 'cap' attribute, or hardware enforced >>>>> limit. If user directly query the 'power1_alarm' attribute without queryng >>>>> above two attributes, driver will use the uninitialized variables to judge. >>>>> In addition, the 'power1_alarm' attribute needs to update power and cap to >>>>> show the real state. >>>>> >>>>> Signed-off-by: Huisong Li >>>>> --- >>>>>   drivers/hwmon/acpi_power_meter.c | 10 ++++++++++ >>>>>   1 file changed, 10 insertions(+) >>>>> >>>>> diff --git a/drivers/hwmon/acpi_power_meter.c b/drivers/hwmon/acpi_power_meter.c >>>>> index 2f1c9d97ad21..4c3314e35d30 100644 >>>>> --- a/drivers/hwmon/acpi_power_meter.c >>>>> +++ b/drivers/hwmon/acpi_power_meter.c >>>>> @@ -396,6 +396,9 @@ static ssize_t show_val(struct device *dev, >>>>>       struct acpi_device *acpi_dev = to_acpi_device(dev); >>>>>       struct acpi_power_meter_resource *resource = acpi_dev->driver_data; >>>>>       u64 val = 0; >>>>> +    int ret; >>>>> + >>>>> +    guard(mutex)(&resource->lock); >>>>>         switch (attr->index) { >>>>>       case 0: >>>>> @@ -423,6 +426,13 @@ static ssize_t show_val(struct device *dev, >>>>>               val = 0; >>>>>           break; >>>>>       case 6: >>>>> +        ret = update_meter(resource); >>>>> +        if (ret) >>>>> +            return ret; >>>>> +        ret = update_cap(resource); >>>>> +        if (ret) >>>>> +            return ret; >>>>> + >>>>>           if (resource->power > resource->cap) >>>>>               val = 1; >>>>>           else >>>> >>>> >>>> While technically correct, the implementation of this attribute defeats its >>>> purpose. It is supposed to reflect the current status as reported by the >>>> hardware. A real fix would be to use the associated notification to set or >>>> reset a status flag, and to report the current value of that flag as reported >>>> by the hardware. >>> I know what you mean. >>> The Notify(power_meter, 0x83) is supposed to meet your proposal IIUC. >>> It's good, but it depands on hardware support notification. >>>> >>>> If there is no notification support, the attribute should not even exist, >>>> unless there is a means to retrieve its value from ACPI (the status itself, >>>> not by comparing temperature values). >>> Currently, the 'power1_alarm' attribute is created just when platform support the power meter meassurement(bit0 of the supported capabilities in _PMC). >>> And it doesn't see if the platform support notifications. >>>  From the current implementation of this driver, this sysfs can also reflect the status by comparing power and cap, >>> which is good to the platform that support hardware limit from some out-of-band mechanism but doesn't support any notification. >>> >> >> The point is that this can also be done from userspace. Hardware monitoring drivers >> are supposed to provide hardware attributes, not software attributes derived from it. >> > So this 'power1_alarm' attribute can be exposed when platform supports hardware enforced limit and notifcations when the hardware limit is enforced, right? > If so, we have to change the condition that driver creates this sysfs interface. This isn't about enforcing anything, it is about reporting an alarm if the power consumed exceeds the maximum configured. Guenter