From patchwork Tue Feb 4 11:09:13 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 13958911 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 6597A20969D; Tue, 4 Feb 2025 11:09:36 +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=1738667377; cv=none; b=oswkgzjmKoNCuPI6gReF8m0glgK+yWESXI4hR6r4/qWTrtvUVWJbAWOUG/nQV/UuTveWJD0shZyfj2nfr0kVeAXdt7jpvbGrzZ4+Rv+EFFvSgHE26qvBds7TTeOImhT8VBEL4sVlYh7iU8MGXLtKTryO28mu2MKGxOoedpnFEBM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738667377; c=relaxed/simple; bh=M9fF2yZwbhd2NgZD12wwwug3mQYv6nfiLMXhmY+0PZM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ohc2GhBXcv9WRd0QUb4aenYQH3tsapn0AVwJdm+OLTLPWynhLdoTK4ZCXsdwQr/9LYFGtXsk8BHzdaJfh7hUKKwORWnw9XUDoYnyP4HBBLXi9X9OQPnp7XvwItZDU3RI5nzVYY+XAm8nC+JcuXXnfRCEsnRoSGUlnm1CEW75Vjo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=jQGewVxX; 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="jQGewVxX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CA3EC4CEDF; Tue, 4 Feb 2025 11:09:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1738667376; bh=M9fF2yZwbhd2NgZD12wwwug3mQYv6nfiLMXhmY+0PZM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jQGewVxXP5zGIq9J4mWul5stjA+03hkSDPUfXtSbFQhhTob7G0YvSfAOk7gHkdgWO vZ5TIYJSBnMUh8W78n7TaBXfGXxvNEPpKJ4jHTDNkyUfbWj5Kvwc1Y/GfOeRd1rTxV 871Nraww1cItAEf86WF6WzYfscfnf4diz8nD5k/o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Danilo Krummrich , Lyude Paul Cc: Greg Kroah-Hartman , 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 , Zijun Hu , linux-usb@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH v2 1/5] driver core: add a faux bus for use when a simple device/bus is needed Date: Tue, 4 Feb 2025 12:09:13 +0100 Message-ID: <2025020424-retrain-recharger-407c@gregkh> X-Mailer: git-send-email 2.48.1 In-Reply-To: <2025020421-poster-moisture-534b@gregkh> References: <2025020421-poster-moisture-534b@gregkh> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=9456; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=M9fF2yZwbhd2NgZD12wwwug3mQYv6nfiLMXhmY+0PZM=; b=owGbwMvMwCRo6H6F97bub03G02pJDOkLv6ZEOAp9z+1lPl69Y3lznNPtvMlbP36wm1xlYlWTH s6ol7ewI5aFQZCJQVZMkeXLNp6j+ysOKXoZ2p6GmcPKBDKEgYtTACYixc6woKOtImWf2sqlzRYH G69X7a9SXRobwbBg2X+2F4n7v7AumTF5bbV9hi/bJ6VoAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 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. Signed-off-by: Greg Kroah-Hartman Reviewed-by: Danilo Krummrich Reviewed-by: Jonathan Cameron Reviewed-by: Lyude Paul --- 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 hanks to Andy - coding style fix thanks to Jonathan - tested that the destroy path actually works drivers/base/Makefile | 2 +- drivers/base/base.h | 1 + drivers/base/faux.c | 196 ++++++++++++++++++++++++++++++++++++ drivers/base/init.c | 1 + include/linux/device/faux.h | 31 ++++++ 5 files changed, 230 insertions(+), 1 deletion(-) create mode 100644 drivers/base/faux.c create mode 100644 include/linux/device/faux.h 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..9b28643afc45 --- /dev/null +++ b/drivers/base/faux.c @@ -0,0 +1,196 @@ +// 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" + +#define MAX_NAME_SIZE 256 /* Max size of a faux_device name */ + +/* + * Internal wrapper structure so we can hold the memory + * for the driver and the name string of the faux device. + */ +struct faux_object { + struct faux_device faux_dev; + const struct faux_driver_ops *faux_ops; + char name[]; +}; +#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_driver_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_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", + .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_PREFER_ASYNCHRONOUS, +}; + +static void faux_device_release(struct device *dev) +{ + struct faux_object *faux_obj = to_faux_object(dev); + + 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 + * + * 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. + * + * Note, when this function is called, the functions specified in struct + * faux_ops will 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 faux_driver_ops *faux_ops) +{ + struct device *dev; + struct faux_object *faux_obj; + struct faux_device *faux_dev; + int name_size; + int ret; + + name_size = strlen(name); + if (name_size > MAX_NAME_SIZE) + return NULL; + + faux_obj = kzalloc(sizeof(*faux_obj) + name_size + 1, GFP_KERNEL); + if (!faux_obj) + return NULL; + + /* Save off the name of the object into local memory */ + memcpy(faux_obj->name, name, name_size); + + /* 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; + dev->parent = &faux_bus_root; + dev->bus = &faux_bus_type; + dev_set_name(dev, "%s", name); + + ret = device_add(dev); + if (ret) { + pr_err("%s: device_add for %s faux device failed with %d\n", + __func__, name, ret); + put_device(dev); + return NULL; + } + + return faux_dev; +} +EXPORT_SYMBOL_GPL(faux_device_create); + +/** + * faux_device_destroy - destroy a faux device + * @faux_dev: faux device to destroy + * + * Unregister and free all memory associated with a faux device that was + * previously created with a call to faux_device_create(). + */ +void faux_device_destroy(struct faux_device *faux_dev) +{ + struct device *dev = &faux_dev->dev; + + if (IS_ERR_OR_NULL(faux_dev)) + return; + + device_del(dev); + + /* The final put_device() will clean up the driver we created 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..2c8ae5bd7ae8 --- /dev/null +++ b/include/linux/device/faux.h @@ -0,0 +1,31 @@ +/* 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 + +struct faux_device { + struct device dev; +}; +#define to_faux_device(x) container_of_const((x), struct faux_device, dev) + +struct faux_driver_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 faux_driver_ops *faux_ops); +void faux_device_destroy(struct faux_device *faux_dev); + +#endif /* _FAUX_DEVICE_H_ */