linux-kernel - Re: [PATCH v2 1/3] drivers: misc: intel_sysid: Add sysid from arch to drivers

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Date:   Fri, 29 Jul 2022 13:43:55 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     kah.jing.lee@...el.com, linux-kernel@...r.kernel.org,
        arnd@...db.de, rafael.j.wysocki@...el.com, tien.sung.ang@...el.com,
        dinh.nguyen@...el.com, Zhou@...ah.com,
        Furong <furong.zhou@...el.com>, Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>
Subject: Re: [PATCH v2 1/3] drivers: misc: intel_sysid: Add sysid from arch
 to drivers

On Thu, Jul 28, 2022 at 11:53:33AM -0500, Pierre-Louis Bossart wrote:
> 
> 
> On 7/28/22 10:59, Greg KH wrote:
> > On Thu, Jul 28, 2022 at 10:37:37AM -0500, Pierre-Louis Bossart wrote:
> >> Thanks for the review Greg,
> >>
> >>>> +static int intel_sysid_probe(struct platform_device *pdev)
> >>>> +{
> >>>> +	struct intel_sysid *sysid;
> >>>> +	struct resource	*regs;
> >>>> +
> >>>> +	sysid = devm_kzalloc(&pdev->dev, sizeof(struct intel_sysid),
> >>>> +		GFP_KERNEL);
> >>>> +	if (!sysid)
> >>>> +		return -ENOMEM;
> >>>> +
> >>>> +	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >>>> +	if (!regs)
> >>>> +		return -ENXIO;
> >>>> +
> >>>> +	sysid->regs = devm_ioremap_resource(&pdev->dev, regs);
> >>>> +	if (IS_ERR(sysid->regs))
> >>>> +		return PTR_ERR(sysid->regs);
> >>>> +
> >>>> +	platform_set_drvdata(pdev, sysid);
> >>>> +
> >>>> +	return devm_device_add_group(&pdev->dev, &intel_sysid_attr_group);
> >>>
> >>> You just raced with userspace and lost.  Please use the default group
> >>> for the platform device.
> >>>
> >>> I need to go remove this function, it should not be used at all as it is
> >>> broken.
> >>
> >> Can you elaborate on the issue and suggested replacement?
> >>
> >> We used this function for the SoundWire sysfs based on your review
> >> comments (2 years ago?) that we should not muck with kobj, and that
> >> function devm_device_add_group() is also used in a probe function.
> > 
> > Use the default_groups pointer in the driver structure.
> 
> did you mean dev_groups?

Yes, sorry, that's the correct name.

> I am not following the idea, for SoundWire all the attributes are really
> device-specific or described by ACPI and cannot be hard-coded in the
> driver structure.

That's what the is_visible() callback is for in the groups structure,
you determine if the attribute is visable or not at runtime, you don't
rely on the driver itself to add/remove attributes, that does not scale
and again, is racy.

thanks,

greg k-h