Messages in this thread | | | Date | Mon, 24 Jun 2013 19:11:35 +0200 | From | Oliver Schinagl <> | Subject | Re: [PATCH 1/2] Initial support for Allwinner's Security ID fuses |
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Hey Greg, On 06/24/13 18:04, Greg KH wrote: > On Mon, Jun 24, 2013 at 11:29:42AM +0200, Maxime Ripard wrote: >> Hi Greg, >> >> On Mon, Jun 17, 2013 at 03:58:47PM -0700, Greg KH wrote: >>> On Mon, Jun 17, 2013 at 10:59:37PM +0200, Oliver Schinagl wrote: >> >> [..] >> >>>> +static int __init sunxi_sid_probe(struct platform_device *pdev) >>>> +{ >>>> + u8 entropy[SID_SIZE]; >>>> + unsigned int i; >>>> + struct resource *res; >>>> + void __iomem *sid_reg_base; >>>> + int ret; >>>> + >>>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); >>>> + sid_reg_base = devm_ioremap_resource(&pdev->dev, res); >>>> + if (IS_ERR(sid_reg_base)) >>>> + return PTR_ERR(sid_reg_base); >>>> + platform_set_drvdata(pdev, sid_reg_base); >>>> + >>>> + ret = device_create_bin_file(&pdev->dev, &sid_bin_attr); >>>> + if (ret) >>>> + return ret; >>> >>> You just raced with userspace, having the file show up after the device >>> was announced to users that it was there. Please use the proper device >>> file api to add default attributes to prevent this from happening. >> >> Sorry if the question looks dumb, but what kind of race can we generate >> here? > > Userspace gets told about the device from the driver core, udev runs and > reads all of the attributes, then your probe function comes along and > adds a new attribute. Userspace will then not know about it at all. > >> The device_create_bin_file is the last call that we make (if we except >> the entropy stuff, but it doesn't really matter here), so after we >> created the file, we have everything properly initialised so that our >> functions can be called, right? >> >> And another dumb question for you, what is the "proper device file API" >> you are referring to ? :) > > Please read Documentation/driver_model/device.txt and see the section on > Attributes for what to do. If you have specific questions after reading > that, please let me know. Since Maxime kinda asked for me, I hope you don't mind me following up.
That doc doesn't mention the binary interface at all. Initially I had both devices up, the 'read' device as a textual representation and added the binary one later. Maxime and I decided the binary one made more sense, as the only textual user would be a human and they don't poke that entry that often.
So what default way exists for binary files or how would that be solved?
Oliver > > thanks, > > greg k-h >
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