linux-kernel - Re: [PATCH v3 18/19] hwmon: (mr75203) add debugfs to read and write temperature coefficients

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Date:   Thu, 1 Sep 2022 09:54:21 +0300
From:   "Farber, Eliav" <farbere@...zon.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
CC:     <jdelvare@...e.com>, <linux@...ck-us.net>, <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>, <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>, "Farber, Eliav" <farbere@...zon.com>
Subject: Re: [PATCH v3 18/19] hwmon: (mr75203) add debugfs to read and write
 temperature coefficients

On 8/31/2022 3:14 PM, Andy Shevchenko wrote:
> On Tue, Aug 30, 2022 at 07:22:11PM +0000, Eliav Farber wrote:
>> This change adds debugfs to read and write temperature sensor 
>> coefficients
>> - g, h, j and cal5.
>>
>> The coefficients can vary between product and product, so it can be very
>> useful to be able to modify them on the fly during the calibration
>> process.
>>
>> e.g.:
>>
>> cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
>> 4096
>>
>> echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g
>
> ...
>
>> +     pvt->dbgfs_dir = debugfs_create_dir(dev_name(dev), NULL);
>
>> +     if (!pvt->dbgfs_dir) {
>> +             dev_err(dev, "Failed to create dbgfs_dir\n");
>> +             return -EINVAL;
>> +     }
>
> No, just don't check the return value of debugfs API calls.
>
Do you mean that I should just do:
debugfs_create_dir(dev_name(dev), NULL);
Can you please explain why it's OK to ignore the return value?

>> +     debugfs_create_file("ts_coeff_h", 0644, pvt->dbgfs_dir, pvt,
>> +                         &pvt_ts_coeff_h_fops);
>> +     debugfs_create_file("ts_coeff_g", 0644, pvt->dbgfs_dir, pvt,
>> +                         &pvt_ts_coeff_g_fops);
>> +     debugfs_create_file("ts_coeff_j", 0644, pvt->dbgfs_dir, pvt,
>> +                         &pvt_ts_coeff_j_fops);
>> +     debugfs_create_file("ts_coeff_cal5", 0644, pvt->dbgfs_dir,  pvt,
>> +                         &pvt_ts_coeff_cal5_fops);
>
> debugfs has helpers for POD types, use them and shrink your code by ~80%.
>
Fixed for v4.
I used debugfs_create_u32() for ts_coeff_h, ts_coeff_g and ts_coeff_j.
For ts_coeff_cal5 I still use debugfs_create_file() because I must make
sure it is not set to 0.

>> +     ret = devm_add_action_or_reset(dev, devm_pvt_ts_dbgfs_remove, 
>> pvt);
>> +     if (ret) {
>> +             dev_err(dev, "failed to add action to remove pvt dbgfs 
>> (%d)\n",
>> +                     ret);
>> +             return ret;
>> +     }
>> +
>> +     return 0;
>
> return devm_add_...
Fixed for v4.

--
Thanks, Eliav