From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 102C9ECAAA1 for ; Thu, 27 Oct 2022 16:48:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235690AbiJ0QsJ (ORCPT ); Thu, 27 Oct 2022 12:48:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230441AbiJ0QsI (ORCPT ); Thu, 27 Oct 2022 12:48:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4EF118F0D9; Thu, 27 Oct 2022 09:48:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5A340623E3; Thu, 27 Oct 2022 16:48:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63DAFC433C1; Thu, 27 Oct 2022 16:48:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666889286; bh=/9duMPb6opUA8O93tCBr6BdnBW8rIFtYXrBYG6hdJKI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Aek07/yCA3fhXdaXFgFhCaXDAGxiqfK4GyGnbMj6SFRKMkPhMkB/UX4QHVHZBkMnY 0xyk6fiCosGcKWzsX3+dGrDdjdQm185fyVc217ZfgVwEfey9Zr+7ToKZtwL0Xrum1m NlXPYASJNbt1rLouNxzynMHhM0RIgcxRTovqeoXQ= Date: Thu, 27 Oct 2022 18:48:04 +0200 From: Greg Kroah-Hartman To: Matthias Schiffer Cc: Arnd Bergmann , linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux@ew.tq-group.com Subject: Re: [RFC 1/5] misc: introduce notify-device driver Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Thu, Oct 27, 2022 at 06:33:33PM +0200, Matthias Schiffer wrote: > On Wed, 2022-10-26 at 16:37 +0200, Greg Kroah-Hartman wrote: > > On Wed, Oct 26, 2022 at 03:15:30PM +0200, Matthias Schiffer wrote: > > > A notify-device is a synchronization facility that allows to query > > > "readiness" across drivers, without creating a direct dependency between > > > the driver modules. The notify-device can also be used to trigger deferred > > > probes. > > > > > > Signed-off-by: Matthias Schiffer > > > --- > > > drivers/misc/Kconfig | 4 ++ > > > drivers/misc/Makefile | 1 + > > > drivers/misc/notify-device.c | 109 ++++++++++++++++++++++++++++++++++ > > > include/linux/notify-device.h | 33 ++++++++++ > > > 4 files changed, 147 insertions(+) > > > create mode 100644 drivers/misc/notify-device.c > > > create mode 100644 include/linux/notify-device.h > > > > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig > > > index 358ad56f6524..63559e9f854c 100644 > > > --- a/drivers/misc/Kconfig > > > +++ b/drivers/misc/Kconfig > > > @@ -496,6 +496,10 @@ config VCPU_STALL_DETECTOR > > > > > > If you do not intend to run this kernel as a guest, say N. > > > > > > +config NOTIFY_DEVICE > > > + tristate "Notify device" > > > + depends on OF > > > + > > > source "drivers/misc/c2port/Kconfig" > > > source "drivers/misc/eeprom/Kconfig" > > > source "drivers/misc/cb710/Kconfig" > > > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile > > > index ac9b3e757ba1..1e8012112b43 100644 > > > --- a/drivers/misc/Makefile > > > +++ b/drivers/misc/Makefile > > > @@ -62,3 +62,4 @@ obj-$(CONFIG_HI6421V600_IRQ) += hi6421v600-irq.o > > > obj-$(CONFIG_OPEN_DICE) += open-dice.o > > > obj-$(CONFIG_GP_PCI1XXXX) += mchp_pci1xxxx/ > > > obj-$(CONFIG_VCPU_STALL_DETECTOR) += vcpu_stall_detector.o > > > +obj-$(CONFIG_NOTIFY_DEVICE) += notify-device.o > > > diff --git a/drivers/misc/notify-device.c b/drivers/misc/notify-device.c > > > new file mode 100644 > > > index 000000000000..42e0980394ea > > > --- /dev/null > > > +++ b/drivers/misc/notify-device.c > > > @@ -0,0 +1,109 @@ > > > +// SPDX-License-Identifier: GPL-2.0-or-later > > > + > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > + > > > +static void notify_device_release(struct device *dev) > > > +{ > > > + of_node_put(dev->of_node); > > > + kfree(dev); > > > +} > > > + > > > +static struct class notify_device_class = { > > > + .name = "notify-device", > > > + .owner = THIS_MODULE, > > > + .dev_release = notify_device_release, > > > +}; > > > + > > > +static struct platform_driver notify_device_driver = { > > [Pruning the CC list a bit, to avoid clogging people's inboxes] > > > > > Ick, wait, this is NOT a platform device, nor driver, so it shouldn't be > > either here. Worst case, it's a virtual device on the virtual bus. > > This part of the code is inspired by mac80211_hwsim, which uses a > platform driver in a similar way, for a plain struct device. Should > this rather use a plain struct device_driver? It should NOT be using a platform device. Again, a platform device should NEVER be used as a child of a device in the tree that is on a discoverable bus. Use the aux bus code if you don't want to create virtual devices with no real bus, that is what it is there for. > Also, what's the virtual bus? Grepping the Linux code and documentation > didn't turn up anything. Look at the stuff that ends up in /sys/devices/virtual/ Lots of users there. > > But why is this a class at all? Classes are a representation of a type > > of device that userspace can see, how is this anything that userspace > > cares about? > > Makes sense, I will remove the class. > > > > > Doesn't the device link stuff handle all of this type of "when this > > device is done being probed, now I can" problems? Why is a whole new > > thing needed? > > The issue here is that (as I understand it) the device link and > deferred probing infrastructore only cares about whether the supplier > device has been probed successfully. > > This is insuffient in the case of the dependency between mwifiex and > hci_uart/hci_mrvl that I want to express: mwifiex loads its firmware > asynchronously, so finishing the mwifiex probe is too early to retry > probing the Bluetooth driver. Welcome to deferred probing hell :) > While mwifiex does create a few devices (ieee80211, netdevice) when the > firmware has loaded, none of these bind to a driver, so they don't > trigger the deferred probes. Using their existence as a condition for > allowing the Bluetooth driver to probe also seems ugly too me > (ieee80211 currently can't be looked up by OF node, and netdevices can > be created and deleted dynamically). > > Because of this, I came to the conclusion that creating and binding a > device specifically for this purpose is a good solution, as it solves > two problems at once: > - The driver bind triggers deferred probes > - The driver allows to look up the device by OF node > > Integrating this with device links might make sense as well, but I > haven't looked much into that yet. Try looking at device links, I think this fits exactly what that solves. If not, please figure out why. thanks, greg k-h