linux-kernel - Re: [PATCH v3 02/19] hwmon: (mr75203) fix VM sensor allocation when "intel, vm-map" not defined

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <71d6d57c-2165-5fe3-515d-9395022921e2@roeck-us.net>
Date:   Wed, 31 Aug 2022 04:48:40 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Farber, Eliav" <farbere@...zon.com>, jdelvare@...e.com,
        robh+dt@...nel.org, p.zabel@...gutronix.de, rtanwar@...linear.com,
        linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     talel@...zon.com, hhhawa@...zon.com, jonnyc@...zon.com,
        hanochu@...zon.com, ronenk@...zon.com, itamark@...zon.com,
        shellykz@...zon.com, shorer@...zon.com, amitlavi@...zon.com,
        almogbs@...zon.com, dkl@...zon.com, andriy.shevchenko@...el.com
Subject: Re: [PATCH v3 02/19] hwmon: (mr75203) fix VM sensor allocation when
 "intel, vm-map" not defined

On 8/30/22 22:49, Farber, Eliav wrote:
> On 8/31/2022 8:36 AM, Guenter Roeck wrote:
>> On 8/30/22 12:21, Eliav Farber wrote:
>>> Bug fix - in case "intel,vm-map" is missing in device-tree ,'num' is set
>>> to 0, and no voltage channel infos are allocated.
>>>
>>> Signed-off-by: Eliav Farber <farbere@...zon.com>
>>> ---
>>>   drivers/hwmon/mr75203.c | 28 ++++++++++++----------------
>>>   1 file changed, 12 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
>>> index 046523d47c29..0e29877a1a9c 100644
>>> --- a/drivers/hwmon/mr75203.c
>>> +++ b/drivers/hwmon/mr75203.c
>>> @@ -580,8 +580,6 @@ static int mr75203_probe(struct platform_device *pdev)
>>>       }
>>>
>>>       if (vm_num) {
>>> -             u32 num = vm_num;
>>> -
>>>               ret = pvt_get_regmap(pdev, "vm", pvt);
>>>               if (ret)
>>>                       return ret;
>>> @@ -594,30 +592,28 @@ static int mr75203_probe(struct platform_device *pdev)
>>>               ret = device_property_read_u8_array(dev, "intel,vm-map",
>>> pvt->vm_idx, vm_num);
>>>               if (ret) {
>>> -                     num = 0;
>>> +                     /*
>>> +                      * Incase intel,vm-map property is not defined, we
>>> +                      * assume incremental channel numbers.
>>> +                      */
>>> +                     for (i = 0; i < vm_num; i++)
>>> +                             pvt->vm_idx[i] = i;
>>>               } else {
>>>                       for (i = 0; i < vm_num; i++)
>>>                               if (pvt->vm_idx[i] >= vm_num ||
>>> -                                 pvt->vm_idx[i] == 0xff) {
>>> -                                     num = i;
>>> +                                 pvt->vm_idx[i] == 0xff)
>>>                                       break;
>>
>> So all vm_idx values from 0x00 to 0xfe would be acceptable ?
>> Does the chip really have that many registers (0x200 + 0x40 + 0x200 * 0xfe) ?
>> Is that documented somewhere ? 
> According to the code vm_num is limited to 32 because the mask is
> only 5 bits:
> 
> #define VM_NUM_MSK    GENMASK(20, 16)
> #define VM_NUM_SFT    16
> vm_num = (val & VM_NUM_MSK) >> VM_NUM_SFT;
> 
> In practice according to the data sheet I have:
> 0 <= VM instances <= 8
> 
Sorry, my bad. I misread the patch and thought the first part of
the if statement was removed.

Anyway, what is the difference between specifying an vm_idx value of
0xff and not specifying anything ? Or, in other words, taking the dt
example, the difference between
	intel,vm-map = [03 01 04 ff ff];
and
	intel,vm-map = [03 01 04];

Thanks,
Guenter