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Date:   Tue, 4 Aug 2020 16:22:50 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Daniel Gutson <daniel@eclypsium.com>
Cc:     Derek Kiernan <derek.kiernan@xilinx.com>,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Richard Hughes <hughsient@gmail.com>,
        Alex Bazhaniuk <alex@eclypsium.com>
Subject: Re: [PATCH] Platform lockdown information in SYSFS
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On Tue, Aug 04, 2020 at 10:50:13AM -0300, Daniel Gutson wrote:
> On Tue, Aug 4, 2020 at 3:41 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Mon, Aug 03, 2020 at 07:04:56PM -0300, Daniel Gutson wrote:
> > > > > > Think of this as an input device.  You don't put the random input
> > > > > > attributes all in one place, you create a new device that represents the
> > > > > > input interface and register that.
> > >
> > > I'm having trouble with this. What's the dev_t for the child devices?
> > > I'm doing
> > >     child_device = device_create(&my_class, &pdev->dev, MKDEV(0, 0),
> > > NULL, "child");
> > > pdev is the pci_device (intel-spi-pci)
> > > dmesg shows
> > >
> > >     sysfs: cannot create duplicate filename '/class/my-class'
> > >     (call trace)
> > >     kobject_add_internal failed for my-class with -EEXIST, don't try
> > > to register things with the same name in the same directory.
> >
> > Without seeing all of your code, I can't tell you what you are doing
> > wrong, but the kernel should be giving you a huge hint here...
> >
> > Don't create duplicate names in the same subdirectory.
> 
> I'm not doing that. One of my questions is if MKDEV(0, 0) is valid for
> create_device, which I inferred so from the documentation.

Yes it is, but that's not the error given to you :)

Many in-kernel users call device_create() with MKDEV(0, 0)

> Here is the listing

<snip>

It's not in any format to read, please never strip leading whitespace,
it hurts my brain...

thanks,

greg k-h