From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) (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 B0B8B26BD95; Tue, 11 Feb 2025 02:49:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.168.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739242192; cv=none; b=GI5joJkfI1Ddvup9bMI/yvZHU3BaxSum9V7qHvlpJA8t5xKOOBNNRJEY1SPB+hfyJuAhnOJa75oNu3Ee+pVsXRu6+RxaCpR3mIH/32kzyD4PgjpWScmTWznAZt5xA4rpSOkE3g8H3wotSx7arcxpYDQZvmPWR3g3gcK1TWZMSPc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739242192; c=relaxed/simple; bh=kjJ8O4tjXQdhjj4nFQFkKD2H0A1/8yzdtEHORG1EByA=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=akThEQSN6kABMtL76udaSj0nR1+0BddXGZP4zrSC7E3HQAwDJrLGUi/svfC1agt3Ch1MnH100TYEZoZdss6WPG2WnzHVzT727j5x26/bnjtnlBMlmkeFuKWBZw61s32ozVWechvT4M63j6bGV+2EgcyWt83WbewnKK5/0xEkXfA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com; spf=pass smtp.mailfrom=quicinc.com; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b=Xwp3MVVJ; arc=none smtp.client-ip=205.220.168.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=quicinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b="Xwp3MVVJ" Received: from pps.filterd (m0279865.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 51B0gRmH031929; Tue, 11 Feb 2025 02:49:12 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= VXNbroVvY4hK2pw57Tv9WyrWjbClpwK8hwkZLx6r5PA=; b=Xwp3MVVJzIlbPmZP JtTLeaQ/IjQ8RMeQKp+Ev3IVPORTRjmOJVagD+lKcJzJPmM+1hI+qwsL0dpJx6dy YXOGecsWvh4W09/eHKbn6uEPy4a1h0XkSiwZX5sw3/Nn97O5C23XNyF5ptWOpIB4 kqAouaumFiTSWpdLNE0UMemwvOCiHveS1+dRh3GvVipVGQzVV12sHjkD4UCCgJh1 SFxhUc91pl+Pkhd6yTL5hBMwcTalUQfk9ZMXHU10YLH1e3RLN9SXBeyEvvj7Let/ k1JVIo7xej1CFgB6vFdfMfmhzqgVTytz5tcE4dgDiDOxKl+e5pePBj8D2JRWVA8G 5y+Ykw== Received: from nasanppmta04.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 44qgtk23ud-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Feb 2025 02:49:11 +0000 (GMT) Received: from nasanex01a.na.qualcomm.com (nasanex01a.na.qualcomm.com [10.52.223.231]) by NASANPPMTA04.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 51B2nBLZ023148 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Feb 2025 02:49:11 GMT Received: from [10.133.33.10] (10.80.80.8) by nasanex01a.na.qualcomm.com (10.52.223.231) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 10 Feb 2025 18:49:07 -0800 Message-ID: Date: Tue, 11 Feb 2025 10:49:05 +0800 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/9] driver core: add a faux bus for use when a simple device/bus is needed To: Greg Kroah-Hartman , , Lyude Paul , "Rafael J. Wysocki" , Danilo Krummrich CC: Alexander Lobakin , Andy Shevchenko , Bjorn Helgaas , Jonathan Cameron , Liam Girdwood , Lukas Wunner , Mark Brown , =?UTF-8?Q?Ma=C3=ADra_Canal?= , Robin Murphy , Simona Vetter , , , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= References: <2025021023-sandstorm-precise-9f5d@gregkh> <2025021026-atlantic-gibberish-3f0c@gregkh> Content-Language: en-US From: Zijun Hu In-Reply-To: <2025021026-atlantic-gibberish-3f0c@gregkh> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nasanex01a.na.qualcomm.com (10.52.223.231) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: GadvhTCLW0IX4yzSVhGl7SMrbX8eMBKY X-Proofpoint-ORIG-GUID: GadvhTCLW0IX4yzSVhGl7SMrbX8eMBKY X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-11_01,2025-02-10_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 suspectscore=0 phishscore=0 impostorscore=0 adultscore=0 clxscore=1011 mlxscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2501170000 definitions=main-2502110014 On 2/10/2025 8:30 PM, Greg Kroah-Hartman wrote: > Many drivers abuse the platform driver/bus system as it provides a > simple way to create and bind a device to a driver-specific set of > probe/release functions. Instead of doing that, and wasting all of the > memory associated with a platform device, here is a "faux" bus that > can be used instead. > > Reviewed-by: Jonathan Cameron > Reviewed-by: Danilo Krummrich > Reviewed-by: Lyude Paul > Reviewed-by: Thomas Weißschuh > Signed-off-by: Greg Kroah-Hartman > --- > v4: - really removed the name logic > - added #include to faux.h > - added parent pointer to api call > - minor documentation updates > - made probe synchronous > v3: - loads of documentation updates and rewrites > - added to the documentation build > - removed name[] array as it's no longer needed > - added faux_device_create_with_groups() > - added functions to get/set devdata > - renamed faux_driver_ops -> faux_device_ops > - made faux_device_ops a const * > - minor cleanups > - tested it, again. > > v2: - renamed bus and root device to just "faux" thanks to Thomas > - removed the one-driver-per-device and now just have one driver > entirely thanks to Danilo > - kerneldoc fixups and additions and string handling bounds checks > thanks to Andy > - coding style fix thanks to Jonathan > - tested that the destroy path actually works > Documentation/driver-api/infrastructure.rst | 6 + > drivers/base/Makefile | 2 +- > drivers/base/base.h | 1 + > drivers/base/faux.c | 232 ++++++++++++++++++++ > drivers/base/init.c | 1 + > include/linux/device/faux.h | 69 ++++++ > 6 files changed, 310 insertions(+), 1 deletion(-) > create mode 100644 drivers/base/faux.c > create mode 100644 include/linux/device/faux.h > > diff --git a/Documentation/driver-api/infrastructure.rst b/Documentation/driver-api/infrastructure.rst > index 3d52dfdfa9fd..35e36fee4238 100644 > --- a/Documentation/driver-api/infrastructure.rst > +++ b/Documentation/driver-api/infrastructure.rst > @@ -41,6 +41,12 @@ Device Drivers Base > .. kernel-doc:: drivers/base/class.c > :export: > > +.. kernel-doc:: include/linux/device/faux.h > + :internal: > + > +.. kernel-doc:: drivers/base/faux.c > + :export: > + > .. kernel-doc:: drivers/base/node.c > :internal: > > diff --git a/drivers/base/Makefile b/drivers/base/Makefile > index 7fb21768ca36..8074a10183dc 100644 > --- a/drivers/base/Makefile > +++ b/drivers/base/Makefile > @@ -6,7 +6,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \ > cpu.o firmware.o init.o map.o devres.o \ > attribute_container.o transport_class.o \ > topology.o container.o property.o cacheinfo.o \ > - swnode.o > + swnode.o faux.o > obj-$(CONFIG_AUXILIARY_BUS) += auxiliary.o > obj-$(CONFIG_DEVTMPFS) += devtmpfs.o > obj-y += power/ > diff --git a/drivers/base/base.h b/drivers/base/base.h > index 8cf04a557bdb..0042e4774b0c 100644 > --- a/drivers/base/base.h > +++ b/drivers/base/base.h > @@ -137,6 +137,7 @@ int hypervisor_init(void); > static inline int hypervisor_init(void) { return 0; } > #endif > int platform_bus_init(void); > +int faux_bus_init(void); > void cpu_dev_init(void); > void container_dev_init(void); > #ifdef CONFIG_AUXILIARY_BUS > diff --git a/drivers/base/faux.c b/drivers/base/faux.c > new file mode 100644 > index 000000000000..531e9d789ee0 > --- /dev/null > +++ b/drivers/base/faux.c > @@ -0,0 +1,232 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (c) 2025 Greg Kroah-Hartman > + * Copyright (c) 2025 The Linux Foundation > + * > + * A "simple" faux bus that allows devices to be created and added > + * automatically to it. This is to be used whenever you need to create a > + * device that is not associated with any "real" system resources, and do > + * not want to have to deal with a bus/driver binding logic. It is > + * intended to be very simple, with only a create and a destroy function > + * available. > + */ > +#include > +#include > +#include > +#include > +#include > +#include > +#include "base.h" > + > +/* > + * Internal wrapper structure so we can hold a pointer to the > + * faux_device_ops for this device. > + */ > +struct faux_object { > + struct faux_device faux_dev; > + const struct faux_device_ops *faux_ops; > +}; > +#define to_faux_object(dev) container_of_const(dev, struct faux_object, faux_dev.dev) > + > +static struct device faux_bus_root = { > + .init_name = "faux", > +}; > + > +static int faux_match(struct device *dev, const struct device_driver *drv) > +{ > + /* Match always succeeds, we only have one driver */ > + return 1; > +} > + > +static int faux_probe(struct device *dev) > +{ > + struct faux_object *faux_obj = to_faux_object(dev); > + struct faux_device *faux_dev = &faux_obj->faux_dev; > + const struct faux_device_ops *faux_ops = faux_obj->faux_ops; > + int ret = 0; > + > + if (faux_ops && faux_ops->probe) > + ret = faux_ops->probe(faux_dev); > + > + return ret; > +} > + > +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_device_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", > + .match = faux_match, > + .probe = faux_probe, > + .remove = faux_remove, > +}; > + > +static struct device_driver faux_driver = { > + .name = "faux_driver", > + .bus = &faux_bus_type, > + .probe_type = PROBE_FORCE_SYNCHRONOUS, > +}; > + > +static void faux_device_release(struct device *dev) > +{ > + struct faux_object *faux_obj = to_faux_object(dev); > + > + kfree(faux_obj); > +} > + > +/** > + * faux_device_create_with_groups - Create and register with the driver > + * core a faux device and populate the device with an initial > + * set of sysfs attributes. > + * @name: The name of the device we are adding, must be unique for > + * all faux devices. > + * @parent: Pointer to a potential parent struct device. If set to > + * NULL, the device will be created in the "root" of the faux > + * device tree in sysfs. > + * @faux_ops: struct faux_device_ops that the new device will call back > + * into, can be NULL. > + * @groups: The set of sysfs attributes that will be created for this > + * device when it is registered with the driver core. > + * > + * Create a new faux device and register it in the driver core properly. > + * If present, callbacks in @faux_ops will be called with the device that > + * for the caller to do something with at the proper time given the > + * device's lifecycle. > + * > + * Note, when this function is called, the functions specified in struct > + * faux_ops can be called before the function returns, so be prepared for > + * everything to be properly initialized before that point in time. > + * > + * Return: > + * * NULL if an error happened with creating the device > + * * pointer to a valid struct faux_device that is registered with sysfs > + */ > +struct faux_device *faux_device_create_with_groups(const char *name, > + struct device *parent, > + const struct faux_device_ops *faux_ops, > + const struct attribute_group **groups) > +{ > + struct faux_object *faux_obj; > + struct faux_device *faux_dev; > + struct device *dev; > + int ret; > + > + faux_obj = kzalloc(sizeof(*faux_obj), GFP_KERNEL); > + if (!faux_obj) > + return NULL; > + > + /* Save off the callbacks so we can use them in the future */ > + faux_obj->faux_ops = faux_ops; > + > + /* Initialize the device portion and register it with the driver core */ > + faux_dev = &faux_obj->faux_dev; > + dev = &faux_dev->dev; > + > + device_initialize(dev); > + dev->release = faux_device_release; > + if (parent) > + dev->parent = parent; > + else > + dev->parent = &faux_bus_root; > + dev->bus = &faux_bus_type; > + dev->groups = groups; > + dev_set_name(dev, "%s", name); > + > + ret = device_add(dev); > + if (ret) { > + pr_err("%s: device_add for faux device '%s' failed with %d\n", > + __func__, name, ret); > + put_device(dev); > + return NULL; > + } > + > + return faux_dev; > +} > +EXPORT_SYMBOL_GPL(faux_device_create_with_groups); > + > +/** > + * faux_device_create - create and register with the driver core a faux device > + * @name: The name of the device we are adding, must be unique for all > + * faux devices. > + * @parent: Pointer to a potential parent struct device. If set to > + * NULL, the device will be created in the "root" of the faux > + * device tree in sysfs. > + * @faux_ops: struct faux_device_ops that the new device will call back > + * into, can be NULL. > + * > + * Create a new faux device and register it in the driver core properly. > + * If present, callbacks in @faux_ops will be called with the device that > + * for the caller to do something with at the proper time given the > + * device's lifecycle. > + * > + * Note, when this function is called, the functions specified in struct > + * faux_ops can be called before the function returns, so be prepared for > + * everything to be properly initialized before that point in time. > + * > + * Return: > + * * NULL if an error happened with creating the device > + * * pointer to a valid struct faux_device that is registered with sysfs > + */ > +struct faux_device *faux_device_create(const char *name, > + struct device *parent, > + const struct faux_device_ops *faux_ops) > +{ > + return faux_device_create_with_groups(name, parent, faux_ops, NULL); > +} > +EXPORT_SYMBOL_GPL(faux_device_create); > + > +/** > + * faux_device_destroy - destroy a faux device > + * @faux_dev: faux device to destroy > + * > + * Unregisters and cleans up a device that was created with a call to > + * faux_device_create() > + */ > +void faux_device_destroy(struct faux_device *faux_dev) > +{ > + struct device *dev = &faux_dev->dev; > + > + if (!faux_dev) > + return; > + > + device_del(dev); > + > + /* The final put_device() will clean up the memory we allocated for this device. */ > + put_device(dev); > +} > +EXPORT_SYMBOL_GPL(faux_device_destroy); > + > +int __init faux_bus_init(void) > +{ > + int ret; > + > + ret = device_register(&faux_bus_root); > + if (ret) { > + put_device(&faux_bus_root); > + return ret; > + } > + > + ret = bus_register(&faux_bus_type); > + if (ret) > + goto error_bus; > + > + ret = driver_register(&faux_driver); > + if (ret) > + goto error_driver; > + > + return ret; > + > +error_driver: > + bus_unregister(&faux_bus_type); > + > +error_bus: > + device_unregister(&faux_bus_root); > + return ret; > +} > diff --git a/drivers/base/init.c b/drivers/base/init.c > index c4954835128c..9d2b06d65dfc 100644 > --- a/drivers/base/init.c > +++ b/drivers/base/init.c > @@ -32,6 +32,7 @@ void __init driver_init(void) > /* These are also core pieces, but must come after the > * core core pieces. > */ > + faux_bus_init(); > of_core_init(); > platform_bus_init(); > auxiliary_bus_init(); > diff --git a/include/linux/device/faux.h b/include/linux/device/faux.h > new file mode 100644 > index 000000000000..9f43c0e46aa4 > --- /dev/null > +++ b/include/linux/device/faux.h > @@ -0,0 +1,69 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (c) 2025 Greg Kroah-Hartman > + * Copyright (c) 2025 The Linux Foundation > + * > + * A "simple" faux bus that allows devices to be created and added > + * automatically to it. This is to be used whenever you need to create a > + * device that is not associated with any "real" system resources, and do > + * not want to have to deal with a bus/driver binding logic. It is > + * intended to be very simple, with only a create and a destroy function > + * available. > + */ > +#ifndef _FAUX_DEVICE_H_ > +#define _FAUX_DEVICE_H_ > + > +#include > +#include > + > +/** > + * struct faux_device - a "faux" device > + * @dev: internal struct device of the object > + * > + * A simple faux device that can be created/destroyed. To be used when a > + * driver only needs to have a device to "hang" something off. This can be > + * used for downloading firmware or other basic tasks. Use this instead of > + * a struct platform_device if the device has no resources assigned to > + * it at all. > + */ > +struct faux_device { > + struct device dev; > +}; > +#define to_faux_device(x) container_of_const((x), struct faux_device, dev) > + > +/** > + * struct faux_device_ops - a set of callbacks for a struct faux_device > + * @probe: called when a faux device is probed by the driver core > + * before the device is fully bound to the internal faux bus > + * code. If probe succeeds, return 0, otherwise return a > + * negative error number to stop the probe sequence from > + * succeeding. > + * @remove: called when a faux device is removed from the system > + * > + * Both @probe and @remove are optional, if not needed, set to NULL. > + */ > +struct faux_device_ops { > + int (*probe)(struct faux_device *faux_dev); > + void (*remove)(struct faux_device *faux_dev); > +}; > + > +struct faux_device *faux_device_create(const char *name, > + struct device *parent, > + const struct faux_device_ops *faux_ops); > +struct faux_device *faux_device_create_with_groups(const char *name, > + struct device *parent, > + const struct faux_device_ops *faux_ops, > + const struct attribute_group **groups); > +void faux_device_destroy(struct faux_device *faux_dev); > + > +static inline void *faux_device_get_drvdata(const struct faux_device *faux_dev) > +{ > + return dev_get_drvdata(&faux_dev->dev); > +} > + > +static inline void faux_device_set_drvdata(struct faux_device *faux_dev, void *data) > +{ > + dev_set_drvdata(&faux_dev->dev, data); > +} > + > +#endif /* _FAUX_DEVICE_H_ */ Reviewed-by: Zijun Hu