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Date:   Mon, 10 Oct 2022 08:24:16 +0200
From:   'Greg Kroah-Hartman' <gregkh@linuxfoundation.org>
To:     Soha Jin <soha@lohu.info>
Cc:     "'Rafael J. Wysocki'" <rafael@kernel.org>,
        'Andy Shevchenko' <andriy.shevchenko@linux.intel.com>,
        'Daniel Scally' <djrscally@gmail.com>,
        'Heikki Krogerus' <heikki.krogerus@linux.intel.com>,
        'Sakari Ailus' <sakari.ailus@linux.intel.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] string: add match_string_nocase() for
 case-insensitive match
Message-ID: <Y0O6kDQ9Bxi9jMfo@kroah.com>
References: <20221009162155.1318-1-soha@lohu.info>
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On Mon, Oct 10, 2022 at 11:02:39AM +0800, Soha Jin wrote:
> Hi Greg,
> > On Mon, Oct 10, 2022 at 12:21:53AM +0800, Soha Jin wrote:
> > > Sometimes we want to make a case-insensitive comparison with strings,
> > > like checking compatible devices in fwnode properties, so this commit
> > > abstracts match_string to __match_string with a compare function. The
> > > original match_string will call __match_string with strcmp, and the
> > > new match_string_nocase will call it with strcasecmp.
> > 
> > Wait, no, fwnode properties are case sensitive, why are you allowing that to
> > be changed?  That sounds like broken firmware to me, right?
> > 
> 
> I am writing regarding the compatibility. In `of_device_is_compatible`, it
> uses `of_compat_cmp` which calls `strcasecmp` to match compatible property.
> 
> As the `fwnode_is_compatible` should be the replacement of the OF way, I
> think we should make the fwnode way and the OF way the same, i.e. either
> both case-insensitive or case-sensitive, to keep the consistency. I am
> afraid that make `of_compat_cmp` case-sensitive may break a great many of
> devices, that is why I am doing this.

Ok, but if you change this with the series, what will break?  What needs
this new case-insensitive comparison that does not work today?

thanks,

greg k-h