linux-kernel - Re: [PATCH v2 1/2] virt: vbox: Add check for device_create

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Message-ID: <172c819f-911f-245b-1f33-da34386f8872@redhat.com>
Date:   Thu, 1 Sep 2022 12:20:03 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>, gregkh@...uxfoundation.org
Cc:     arnd@...db.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] virt: vbox: Add check for device_create_file

Hi,

On 9/1/22 12:16, Jiasheng Jiang wrote:
> On Thu, Sep 01, 2022 at 05:39:46PM +0800, Greg KH wrote:
>>> -	device_create_file(dev, &dev_attr_host_version);
>>> -	device_create_file(dev, &dev_attr_host_features);
>>> +
>>> +	ret = device_create_file(gdev->dev, &dev_attr_host_features);
>>> +	if (ret)
>>> +		goto err_unregister_misc_device_user;
>>> +	ret = device_create_file(gdev->dev, &dev_attr_host_version);
>>> +	if (ret)
>>> +		goto err_remove_file_features;
>>>  
>>>  	vbg_info("vboxguest: misc device minor %d, IRQ %d, I/O port %x, MMIO at %pap (size %pap)\n",
>>>  		 gdev->misc_device.minor, pci->irq, gdev->io_port,
>>> @@ -399,6 +404,8 @@ static int vbg_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
>>>  
>>>  	return 0;
>>>  
>>> +err_remove_file_features:
>>> +	device_remove_file(gdev->dev, &dev_attr_host_features);
>> Please make a patch series that is linked together, the one you just did
>> was not properly threaded at all (hint, use git send-email).
>>
>> And again, this is not the correct way to solve this issue, use a
>> default attribute group for the driver instead.  No driver should ever
>> be adding or removing files individually like this.
> 
> Need I use the group to replace the individually removal in
> vbg_pci_remove() too?

The idea is to do a change similar to this one:

https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?id=4b0133533e82af25d6aaf9d0c7b2a5af388feb74

Setting the driver's .dev_groups field will automatically
add the attributes when probe() succeeds and they will
also automatically be removed before the driver's remove()
function gets called.

So after this change you can remove both the manual add
calls from probe() as well as remove the remove calls
from vbg_pci_remove().

Regards,

Hans