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 4129FFA3744 for ; Fri, 28 Oct 2022 09:11:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229965AbiJ1JLL (ORCPT ); Fri, 28 Oct 2022 05:11:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229456AbiJ1JLI (ORCPT ); Fri, 28 Oct 2022 05:11:08 -0400 Received: from mx1.tq-group.com (mx1.tq-group.com [93.104.207.81]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CDA2664EB; Fri, 28 Oct 2022 02:11:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1666948265; x=1698484265; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=ly7+HAQfpn4/xVSZsitzehQ1kryk3ZFPDVcAIydFii4=; b=XvtEBYmYzytwtC61ooiRceBwBgXspOD9IUeU3iqOSSEZvh5Nis6skHHe ZWFK9etgIejgT7176esS8Lvp5LxHr4S11NImbniH+pPsutBoI5TOhQuve gz7mLExQ6Wy6OTTx48bjJwHjmUEwc5+s7O9Ff/6VSSHSFWzZvRXMNKu7A ZBoF/ZraopfxrbJqYRYby2/vvDOIAhG74qPMOL3OK0iB9SBwIAWwG++QK AYvlaixQtZZhIR2IoG7W11g+jSgi+xZuy8EZMJPdvAqzCRIr0a8hEkJFT 5E6T8ZaDFnV0db9rqm6gxdKc2aVn83kcl99cQXac2gxBM1qlXEPcjqxt1 g==; X-IronPort-AV: E=Sophos;i="5.95,220,1661810400"; d="scan'208";a="27033332" Received: from unknown (HELO tq-pgp-pr1.tq-net.de) ([192.168.6.15]) by mx1-pgp.tq-group.com with ESMTP; 28 Oct 2022 11:11:00 +0200 Received: from mx1.tq-group.com ([192.168.6.7]) by tq-pgp-pr1.tq-net.de (PGP Universal service); Fri, 28 Oct 2022 11:11:00 +0200 X-PGP-Universal: processed; by tq-pgp-pr1.tq-net.de on Fri, 28 Oct 2022 11:11:00 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tq-group.com; i=@tq-group.com; q=dns/txt; s=key1; t=1666948260; x=1698484260; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=ly7+HAQfpn4/xVSZsitzehQ1kryk3ZFPDVcAIydFii4=; b=BzL7Du+GrJ33ddRfb0rEy9z4szhrHdpVMmnz3ZKoB8xwMJkMlUWlUe0e pJh5eWuwverB3RwMxjhWFeC5Bdu9bc64jqD3KVrBrDPjEbpIPm6hp8sTA EwIqXigmkicKLfoBdqPxNijxW0QlT7bOO3f5t7YI1JVLip7VLX6/qg43a a/Z2Ual/Tdfa4hBw42Z0tIaJHrJLdqO9BmHcmXqEoihicM3YYINdt2N5b dlnUa02B9w993RoJPhKhLtk0LfLot1jO3MkAvd2UaC6NUyHWuVvdsH4rL wucLRkhoVuMHNJBX3cv0hPjTyc6P5/XE2qwyub9ufBKlKUHR5uU2VIEGA Q==; X-IronPort-AV: E=Sophos;i="5.95,220,1661810400"; d="scan'208";a="27033330" Received: from vtuxmail01.tq-net.de ([10.115.0.20]) by mx1.tq-group.com with ESMTP; 28 Oct 2022 11:11:00 +0200 Received: from schifferm-ubuntu (SCHIFFERM-M2.tq-net.de [10.121.49.14]) by vtuxmail01.tq-net.de (Postfix) with ESMTPA id 36CBF280056; Fri, 28 Oct 2022 11:11:00 +0200 (CEST) Message-ID: <2983d3fc9516695da57d389b0d90cb2a748c3bee.camel@ew.tq-group.com> Subject: Re: [RFC 1/5] misc: introduce notify-device driver From: Matthias Schiffer To: Greg Kroah-Hartman 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 Date: Fri, 28 Oct 2022 11:10:58 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2022-10-27 at 18:48 +0200, Greg Kroah-Hartman wrote: > 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. Thanks, the auxiliary bus seems to be what I'm looking 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. According to [1], what triggers device link state changes is the binding of drivers. As mentioned, this doesn't help in the mwifiex case: The mwifiex probe does not wait for the firmware to load, as the probe would otherwise take too long (see [2]). So unless we want to extend the device link facility with a manual mode where the supplier explicitly sets the link to a "ready" state, we still need to extend mwifiex with a child device to attach the link to, triggering the state change by binding it to a driver at the right moment. Which is what this patch implements in a generic way (just without device links so far). Thanks, Matthias [1] https://www.kernel.org/doc/html/latest/driver-api/device_link.html#state-machine [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=59a4cc2539076f868f2a3fcd7a3385a26928a27a