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Date: Wed, 20 Apr 2022 20:04:21 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: "Williams, Dan J" <dan.j.williams@intel.com>,
	Hans de Goede <hdegoede@redhat.com>,
	"markgross@kernel.org" <markgross@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, X86 ML <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Jonathan Corbet <corbet@lwn.net>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	"Joseph, Jithu" <jithu.joseph@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
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	"patches@lists.linux.dev" <patches@lists.linux.dev>,
	"Shankar, Ravi V" <ravi.v.shankar@intel.com>
Subject: Re: [PATCH v3 03/11] platform/x86/intel/ifs: Create device for Intel
 IFS (In Field Scan)
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In-Reply-To: <578be5d8874f4942a58adf5f64c4e817@intel.com>

On Wed, Apr 20, 2022 at 05:57:04PM +0000, Luck, Tony wrote:
> >> 	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?

How many do you have?

And why is a directory needed for just one tiny driver type?

thanks,

greg k-h