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From:   Daniel Gutson <daniel@eclypsium.com>
Date:   Tue, 4 Aug 2020 10:50:13 -0300
Message-ID: <CAFmMkTE1PHPrZwnH7DKFW145dn01LhydTbL7HPTO+_zKA+P61Q@mail.gmail.com>
Subject: Re: [PATCH] Platform lockdown information in SYSFS
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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>
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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.
Here is the listing

static ssize_t howareyou_show(struct class *class, struct class_attribute *attr,
    char *buf)
{
return sprintf(buf, "%s\n", "How are you?");
}
static CLASS_ATTR_RO(howareyou);

static struct class my_class = {
        .name =         "my-class",
        .owner =        THIS_MODULE,
};

struct device* child_device;


static int mypci_probe(struct pci_dev *pdev,
       const struct pci_device_id *id)
{
int ret;

ret = pcim_enable_device(pdev);
if (ret)
return ret;

ret = class_register(&my_class);
if (ret < 0)
return ret;


pr_info("DFG: Recognized. DID: %lx\n", (unsigned long int)id->driver_data);
pr_info("DFG: device DID: %lx\n", (unsigned long int)pdev->device);

ret = class_create_file(&my_class, &class_attr_howareyou);
if (ret != 0)
{
    pr_err("DFG class create file error: %d\n", ret);
        class_unregister(&my_class);
        return ret;
}

    child_device = device_create(&my_class, &pdev->dev, MKDEV(0, 0),
NULL, "child");
if (child_device == NULL)
{
    pr_err("DFG error child device NULL");
}

return ret;
}

static void mypci_remove(struct pci_dev *pdev)
{
/* I tried enabling and disabling this code
if (child_device != NULL)
{
put_device(child_device);
device_unregister(child_device);
}
*/

    class_remove_file(&my_class, &class_attr_howareyou);
    class_unregister(&my_class);
}

static const struct pci_device_id my_dids[] = {
{ PCI_VDEVICE(INTEL, 0xa30e), (unsigned long)0xa30e },
{ PCI_VDEVICE(INTEL, 0xa324), (unsigned long)0xa324 },
{ },
};
MODULE_DEVICE_TABLE(pci, my_dids);

static struct pci_driver my_pci_driver = {
.name = "dfg-pci",
.id_table = my_dids,
.probe = mypci_probe,
.remove = mypci_remove,
};

module_pci_driver(my_pci_driver);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Daniel Gutson <daniel.gutson@eclypsium.com>");


>
> thanks,
>
> greg k-h


-- 
Daniel Gutson
Argentina Site Director
Enginieering Director
Eclypsium

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