From patchwork Mon Feb 3 14:25:17 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: 13957595 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 BDAA420A5DE; Mon, 3 Feb 2025 14:25:36 +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=1738592736; cv=none; b=Ud52NpYU5OmljIhp5druQALc8Hi/UocfFkdOb3y0BdORwxyNTmCWOYa4uw/3YrDn7iRi2zXTZ2EhXX282d+By3DcLV71IyUUb9jIaDnPwUj/oF1WoQi+Lz3xMpSTPDukByVnRkowXSCvPVOFPcsdmSRNBxBNMJ2DTSyxNeSvGVo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738592736; c=relaxed/simple; bh=+nmWW1bZ6UVBEYR5zkaQ0IEV8ri+eM8vDjtD4wRg5i4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=g/RKLAsv+ADvHSJxQa5w1cqXaE2dlysGdajOb838NO6Nnx6AKKtnPJQiJ4FiM4ZFZ6T60KSM4/P2q2YK9WXij3Jtyxf2piMz8c+8e840KD+14EAJKwKt9YrCeE0rHig018lbQ+6zM/LDrSCk+7adZBLPrAOmUSBTf7cR+SHXsCk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Fc2BwV3I; 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="Fc2BwV3I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8401EC4CEE3; Mon, 3 Feb 2025 14:25:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1738592736; bh=+nmWW1bZ6UVBEYR5zkaQ0IEV8ri+eM8vDjtD4wRg5i4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Fc2BwV3ItPgbMwUt1lzN5YfUPbXowxuV59LxB110WhX01ofrPGo+P71Rp2ubbz98C Ul4m6tYtyFTTi1ps5Q6AOTIrUfFQUN684Tr7hJM0mTr0z5H22xPCcyOb7hsI43ko4a 8auXMwRYv2tITXtNpFAFuHZBGFMMPfBlnCeZ7OKc= From: Greg Kroah-Hartman To: "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-kernel@vger.kernel.org, linux-usb@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH 1/3] driver core: add a faux bus for use when a simple device/bus is needed Date: Mon, 3 Feb 2025 15:25:17 +0100 Message-ID: <2025020326-backer-vendetta-7094@gregkh> X-Mailer: git-send-email 2.48.1 In-Reply-To: <2025020324-thermal-quilt-1bae@gregkh> References: <2025020324-thermal-quilt-1bae@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=8853; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=+nmWW1bZ6UVBEYR5zkaQ0IEV8ri+eM8vDjtD4wRg5i4=; b=owGbwMvMwCRo6H6F97bub03G02pJDOkLLl5L2ymdfGXanmuzamZeEA1RPLn/1teph96vzOEM7 N2XuMEztyOWhUGQiUFWTJHlyzaeo/srDil6GdqehpnDygQyhIGLUwAmopzCMFeq8m/2vQUe6upu mj9K65YE/bY+IMswP0epWaOuSKxspWDzJbcHsk+zGzYlAgA= 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 --- drivers/base/Makefile | 2 +- drivers/base/base.h | 1 + drivers/base/faux.c | 189 ++++++++++++++++++++++++++++++++++++ drivers/base/init.c | 1 + include/linux/device/faux.h | 33 +++++++ 5 files changed, 225 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..0eba89a5cd57 --- /dev/null +++ b/drivers/base/faux.c @@ -0,0 +1,189 @@ +// 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. Whenever you need a device that is not "real", + * use this interface instead of even thinking of using a platform device. + * + */ +#include +#include +#include +#include +#include +#include "base.h" + +/* + * 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; + struct device_driver driver; + const struct faux_driver_ops *faux_ops; + char name[]; +}; +#define to_faux_object(x) container_of_const(dev, struct faux_object, faux_dev.dev); + +static struct device faux_bus_root = { + .init_name = "faux_bus", +}; + +static int faux_match(struct device *dev, const struct device_driver *drv) +{ + struct faux_object *faux_obj = to_faux_object(dev); + + /* Match is simple, strcmp()! */ + return (strcmp(faux_obj->name, drv->name) == 0); +} + +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_bus", + .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, + struct module *owner) +{ + 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; + drv->bus = &faux_bus_type; + drv->probe_type = PROBE_PREFER_ASYNCHRONOUS; + + ret = driver_register(drv); + if (ret) { + pr_err("%s: driver_register for %s faux driver failed with %d\n", + __func__, name, ret); + kfree(faux_obj); + return NULL; + } + + /* 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. + */ +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 error; + + error = device_register(&faux_bus_root); + if (error) { + put_device(&faux_bus_root); + return error; + } + + error = bus_register(&faux_bus_type); + if (error) + device_unregister(&faux_bus_root); + + return error; +} 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..b1a51fbb6f39 --- /dev/null +++ b/include/linux/device/faux.h @@ -0,0 +1,33 @@ +/* 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. Whenever you need a device that is not "real", + * use this interface instead of even thinking of using a platform device. + * + */ +#ifndef _FAUX_DEVICE_H_ +#define _FAUX_DEVICE_H_ + +#include +#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); +}; + +#define faux_device_create(name, faux_ops) __faux_device_create(name, faux_ops, THIS_MODULE) +struct faux_device *__faux_device_create(const char *name, + struct faux_driver_ops *faux_ops, + struct module *module); +void faux_device_destroy(struct faux_device *faux_dev); + +#endif /* _FAUX_DEVICE_H_ */