Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752599Ab3FZJWe (ORCPT ); Wed, 26 Jun 2013 05:22:34 -0400 Received: from mail-pb0-f42.google.com ([209.85.160.42]:41583 "EHLO mail-pb0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751619Ab3FZJWa (ORCPT ); Wed, 26 Jun 2013 05:22:30 -0400 MIME-Version: 1.0 In-Reply-To: <20130624160440.GA15201@kroah.com> References: <1371502778-15849-1-git-send-email-oliver+list@schinagl.nl> <1371502778-15849-2-git-send-email-oliver+list@schinagl.nl> <20130617225847.GA9494@kroah.com> <20130624092942.GG26008@lukather> <20130624160440.GA15201@kroah.com> Date: Wed, 26 Jun 2013 11:22:30 +0200 X-Google-Sender-Auth: KORp-k7-ncyLI8Rq_yYJz8HuBEI Message-ID: Subject: Re: [PATCH 1/2] Initial support for Allwinner's Security ID fuses From: Geert Uytterhoeven To: Greg KH Cc: Maxime Ripard , Oliver Schinagl , Arnd Bergmann , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , andy.shevchenko@gmail.com, Russell King , Linus Walleij , linux-sunxi@googlegroups.com, Oliver Schinagl , rtc-linux@googlegroups.com, "kernel-janitors@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3623 Lines: 84 On Mon, Jun 24, 2013 at 6:04 PM, Greg KH wrote: > On Mon, Jun 24, 2013 at 11:29:42AM +0200, Maxime Ripard wrote: >> 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. Woops, then we have plenty of existing drivers to fix, e.g. all/most RTC drivers exposing an NVRAM file through sysfs: $ git grep -w sysfs_create_bin_file drivers/rtc/ drivers/rtc/rtc-cmos.c: retval = sysfs_create_bin_file(&dev->kobj, &nvram); drivers/rtc/rtc-ds1305.c: status = sysfs_create_bin_file(&spi->dev.kobj, &nvram); drivers/rtc/rtc-ds1307.c: err = sysfs_create_bin_file(&client->dev.kobj, ds1307->nvram); drivers/rtc/rtc-ds1511.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &ds1511_nvram_attr); drivers/rtc/rtc-ds1553.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &ds1553_nvram_attr); drivers/rtc/rtc-ds1742.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &pdata->nvram_attr); drivers/rtc/rtc-m48t59.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &m48t59_nvram_attr); drivers/rtc/rtc-rp5c01.c: error = sysfs_create_bin_file(&dev->dev.kobj, &priv->nvram_attr); drivers/rtc/rtc-stk17ta8.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &stk17ta8_nvram_attr); drivers/rtc/rtc-tx4939.c: ret = sysfs_create_bin_file(&pdev->dev.kobj, &tx4939_rtc_nvram_attr); Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/