linux-kernel - RE: [PATCH v3 03/11] platform/x86/intel/ifs: Create device for Intel IFS (In Field Scan)

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Message-ID: <578be5d8874f4942a58adf5f64c4e817@intel.com>
Date:   Wed, 20 Apr 2022 17:57:04 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "Williams, Dan J" <dan.j.williams@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Jonathan Corbet <corbet@....net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v3 03/11] platform/x86/intel/ifs: Create device for Intel
 IFS (In Field Scan)

>> 	ifs_class = class_create(THIS_MODULE, "intel_ifs");
>
> Why do you need a class?  Why not just use a misc device?  Saves you
> loads of boilerplate code that is sometimes tricky to get correct.

It didn't feel like a "ton" of boiler plate. Just class_create()/class_destroy()
for the class itself. And

	class_for_each_device(ifs_class, NULL, NULL, ifs_device_unregister);

to clean up devices on exit (or error cleanup in init()).


I thought I needed a class to make a directory for my per-test directories to live in:

$ ls -l /sys/devices/virtual/intel_ifs
total 0
drwxr-xr-x 3 root root 0 Apr 20 13:36 ifs0
drwxr-xr-x 3 root root 0 Apr 20 13:36 ifs1

Can I do that with a misc device?

Or is it ok for them all to sit at the top level of /sys/devices/virtual?

-Tony