From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0F5B013C9D4; Tue, 4 Feb 2025 10:20:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738664453; cv=none; b=qoKGLGtYQnlLbLAet1F4mAZZN58I58ixS3b7x5TTDfIkhPUncFbQgoGQTUsPesxkyCRtOv846r2lX/gUouz3oGxOz3e0SGJk9x3bAKIKN6j/jkC4xod7sgqQrMZE2Pl2XpUQ9FxJJynfVYR0fYRrMjCbse6SBXkd4yyrdEvPbH0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738664453; c=relaxed/simple; bh=1yiPGmbegji3QalyzllDOR9ellvItD0yt1XHJ6KdoD8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=C4rByyolknNE2g2ehTMUFDNUJF1wlQZRcFFwj+EcmktBHzMR4+uV/BPkHfYGxc+PdVStwnbUGVKoWOVOw7VWSipDYzB4skADO+jMeWR587M1zNj6eQr9V9Z9BRpieK5auK/VpkRjccHBxKzOdLhUwMOrhHnxu4hGW9EbZDFkYbs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=y0qq21rn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="y0qq21rn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9A3DC4CEDF; Tue, 4 Feb 2025 10:20:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1738664452; bh=1yiPGmbegji3QalyzllDOR9ellvItD0yt1XHJ6KdoD8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=y0qq21rnquPUBBmOLU7ovddIAcDuVm4cbdvXWdCDO1BsPUarnc/uFXbizSgHf9VTP audSa7nofutOqhlLDULdkCD7mfdBaZ/9rapVI9slVxqes0MPnZIgHQN9jWNBm4o8IC qOYkV2+AlXR+LKp72m75DKI1/msClUaXdYeE3cvQ= Date: Tue, 4 Feb 2025 11:20:43 +0100 From: Greg Kroah-Hartman To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: "Rafael J. Wysocki" , Danilo Krummrich , Lyude Paul , Alexander Lobakin , Andy Shevchenko , Bjorn Helgaas , Jonathan Cameron , Liam Girdwood , Lukas Wunner , Mark Brown , =?iso-8859-1?Q?Ma=EDra?= Canal , Robin Murphy , Simona Vetter , Zijun Hu , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: Re: [PATCH 1/3] driver core: add a faux bus for use when a simple device/bus is needed Message-ID: <2025020430-polyester-unwind-5f9e@gregkh> References: <2025020324-thermal-quilt-1bae@gregkh> <2025020326-backer-vendetta-7094@gregkh> <127f992b-1c53-49e1-8939-65b1d086fac5@t-8ch.de> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <127f992b-1c53-49e1-8939-65b1d086fac5@t-8ch.de> On Tue, Feb 04, 2025 at 11:08:11AM +0100, Thomas Weißschuh wrote: > On 2025-02-03 15:25:17+0100, Greg Kroah-Hartman wrote: > > +static void faux_remove(struct device *dev) > > +{ > > + struct faux_object *faux_obj = to_faux_object(dev); > > + struct faux_device *faux_dev = &faux_obj->faux_dev; > > + const struct faux_driver_ops *faux_ops = faux_obj->faux_ops; > > + > > + if (faux_ops && faux_ops->remove) > > + faux_ops->remove(faux_dev); > > +} > > + > > +static const struct bus_type faux_bus_type = { > > + .name = "faux_bus", > > Is the _bus suffix intentional? It was intentional. > Other busses don't have it. True. Naming is hard. I guess /sys/bus/faux/ makes sense, I will go rename it. But for the "root" device, does /sys/devices/faux_bus/ make sense, or should it be /sys/devices/faux/ as well? I'm now leaning toward the latter... > > + .match = faux_match, > > + .probe = faux_probe, > > + .remove = faux_remove, > > +}; > > + > > +static void faux_device_release(struct device *dev) > > +{ > > + struct faux_object *faux_obj = to_faux_object(dev); > > + struct device_driver *drv = &faux_obj->driver; > > + > > + /* > > + * Now that the device is going away, it has been unbound from the > > + * driver we created for it, so it is safe to unregister the driver from > > + * the system. > > + */ > > + driver_unregister(drv); > > + > > + kfree(faux_obj); > > +} > > + > > +/** > > + * __faux_device_create - create and register a faux device and driver > > + * @name: name of the device and driver we are adding > > + * @faux_ops: struct faux_driver_ops that the new device will call back into, can be NULL > > + * @owner: module owner of the device/driver > > + * > > + * Create a new faux device and driver, both with the same name, and register > > + * them in the driver core properly. The probe() callback of @faux_ops will be > > + * called with the new device that is created for the caller to do something > > + * with. > > + */ > > +struct faux_device *__faux_device_create(const char *name, > > + struct faux_driver_ops *faux_ops, > > const > > > + struct module *owner) > > What about attributes? What in-kernel user of this wants an attribute for such a device? And again, if we find one, we can make a faux_device_create_groups() call that takes a pointer to an attribute group structure if it's really needed. > > > +{ > > + struct device_driver *drv; > > + struct device *dev; > > + struct faux_object *faux_obj; > > + struct faux_device *faux_dev; > > + int ret; > > + > > + faux_obj = kzalloc(sizeof(*faux_obj) + strlen(name) + 1, GFP_KERNEL); > > + if (!faux_obj) > > + return NULL; > > + > > + /* Save off the name of the object into local memory */ > > + strcpy(faux_obj->name, name); > > + > > + /* Initialize the driver portion and register it with the driver core */ > > + faux_obj->faux_ops = faux_ops; > > + drv = &faux_obj->driver; > > + > > + drv->owner = owner; > > + drv->name = faux_obj->name; > > Assuming most names are constant, this would be better with kstrdup_const(). > Which is also used by dev_set_name() under the hood. I've now removed the additional driver, but note that this is just a pointer assignment, which is fine to do here as the lifespan of faux_obj->name outlived the driver structure's lifespan. thanks for the review, much appreciated! greg k-h