linux-kernel - Re: [PATCH v2 12/14] platform/x86/intel/ifs: Add current

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Message-ID: <Y3Jf1GmQKy3Dnz6V@agluck-desk3.sc.intel.com>
Date:   Mon, 14 Nov 2022 07:33:40 -0800
From:   Tony Luck <tony.luck@...el.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thiago Macieira <thiago.macieira@...el.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...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>,
        "Jimenez Gonzalez, Athenas" <athenas.jimenez.gonzalez@...el.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>
Subject: Re: [PATCH v2 12/14] platform/x86/intel/ifs: Add current_batch sysfs
 entry

On Mon, Nov 14, 2022 at 08:15:58AM +0100, gregkh@...uxfoundation.org wrote:
> On Sun, Nov 13, 2022 at 12:48:40PM +0100, Borislav Petkov wrote:
> > Replying to both with one mail because it still feels like there's a
> > misunderstanding.
> > 
> > On Sun, Nov 13, 2022 at 08:37:32AM +0100, gregkh@...uxfoundation.org wrote:
> > > No, please do not force the driver to resolve a filename path in the
> > > kernel.
> > 
> > No, I don't mean to do any filename path resolving - all I suggest is to
> > echo into sysfs the full filename instead of the number. I.e., this:
> > 
> > for i in $(ls /lib/firmware/intel/ifs_0/*.scan);
> > do
> > 	echo $i /sys/devices/virtual/misc/intel_ifs_0/current_batch

Bug ... $i is a full path here. I think Boris meant:

	echo ${i##*/} > /sys/devices/virtual/misc/intel_ifs_0/current_batch

> > done
> 
> Sorry, yes, that is fine, I was objecting to the previous "write any
> path/file to the sysfs entry and the kernel will parse it" that was
> happening in the original series.  A filename, without a path, that
> always loads from the existing in-kernel firmware path locations is
> fine.

Just to set the record straight, the previous patch did *not* allow any
path/file. It seems that you misread that original patch.

Whole thing is here:

https://lore.kernel.org/all/20220708151938.986530-1-jithu.joseph@intel.com/

But the important bits are in the commit comment:

  Change the semantics of the "reload" file. Writing "1" keeps the legacy
  behavior to reload from the default "ff-mm-ss.scan" file, but now interpret
  other strings as a filename to be loaded from the /lib/firmware/intel/ifs
  directory.

and the code:

+		if (strchr(file_name, '/'))
+			goto done;

Is there some other function/macro that we should have used to check
that user input was a filename and not a pathname that would have made
this clearer?

I do agree that overloading semantics of the "reload" was icky. Changing
the name of the sysfs file and dropping the "1" means reload default has
made this a better interface.

-Tony