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Message-ID: <5e7aff1e-82de-2ec4-4d30-2b1f37ed2eed@gmx.net>
Date: Wed, 13 Sep 2023 22:58:12 +0200
From: Stefan Wahren <wahrenst@....net>
To: Umang Jain <umang.jain@...asonboard.com>,
linux-staging@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org,
linux-rpi-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Stefan Wahren <stefan.wahren@...e.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Florian Fainelli <f.fainelli@...il.com>,
Adrien Thierry <athierry@...hat.com>,
Dan Carpenter <error27@...il.com>,
Dave Stevenson <dave.stevenson@...pberrypi.com>,
Kieran Bingham <kieran.bingham@...asonboard.com>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH v11 1/5] staging: vc04_services: vchiq_arm: Add new bus
type and device type
Hi Umang,
Am 13.09.23 um 21:53 schrieb Umang Jain:
> The devices that the vchiq interface registers (bcm2835-audio,
> bcm2835-camera) are implemented and exposed by the VC04 firmware.
> The device tree describes the VC04 itself with the resources required
> to communicate with it through a mailbox interface. However, the
> vchiq interface registers these devices as platform devices. This
> also means the specific drivers for these devices are getting
> registered as platform drivers. This is not correct and a blatant
> abuse of platform device/driver.
>
> Add a new bus type, vchiq_bus_type and device type (struct vchiq_device)
> which will be used to migrate child devices that the vchiq interfaces
> creates/registers from the platform device/driver.
>
> Signed-off-by: Umang Jain <umang.jain@...asonboard.com>
> ---
> drivers/staging/vc04_services/Makefile | 1 +
> .../interface/vchiq_arm/vchiq_device.c | 111 ++++++++++++++++++
> .../interface/vchiq_arm/vchiq_device.h | 54 +++++++++
> 3 files changed, 166 insertions(+)
> create mode 100644 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> create mode 100644 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
>
> diff --git a/drivers/staging/vc04_services/Makefile b/drivers/staging/vc04_services/Makefile
> index 44794bdf6173..2d071e55e175 100644
> --- a/drivers/staging/vc04_services/Makefile
> +++ b/drivers/staging/vc04_services/Makefile
> @@ -5,6 +5,7 @@ vchiq-objs := \
> interface/vchiq_arm/vchiq_core.o \
> interface/vchiq_arm/vchiq_arm.o \
> interface/vchiq_arm/vchiq_debugfs.o \
> + interface/vchiq_arm/vchiq_device.o \
> interface/vchiq_arm/vchiq_connected.o \
>
> ifdef CONFIG_VCHIQ_CDEV
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> new file mode 100644
> index 000000000000..aad55c461905
> --- /dev/null
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * vchiq_device.c - VCHIQ generic device and bus-type
> + *
> + * Copyright (c) 2023 Ideas On Board Oy
> + */
> +
> +#include <linux/device/bus.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/of_device.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +
> +#include "vchiq_device.h"
> +
> +static int vchiq_bus_type_match(struct device *dev, struct device_driver *drv)
> +{
> + if (dev->bus == &vchiq_bus_type &&
> + strcmp(dev_name(dev), drv->name) == 0)
> + return 1;
> +
> + return 0;
> +}
> +
> +static int vchiq_bus_uevent(const struct device *dev, struct kobj_uevent_env *env)
> +{
> + const struct vchiq_device *device = container_of_const(dev, struct vchiq_device, dev);
> +
> + return add_uevent_var(env, "MODALIAS=%s", dev_name(&device->dev));
> +}
> +
> +static int vchiq_bus_probe(struct device *dev)
> +{
> + struct vchiq_device *device = to_vchiq_device(dev);
> + struct vchiq_driver *driver = to_vchiq_driver(dev->driver);
> + int ret;
> +
> + ret = driver->probe(device);
> + if (ret == 0)
> + return 0;
> +
> + return ret;
> +}
> +
> +struct bus_type vchiq_bus_type = {
> + .name = "vchiq-bus",
> + .match = vchiq_bus_type_match,
> + .uevent = vchiq_bus_uevent,
> + .probe = vchiq_bus_probe,
> +};
> +
> +static void vchiq_device_release(struct device *dev)
> +{
> + struct vchiq_device *device = to_vchiq_device(dev);
> +
> + kfree(device);
> +}
> +
> +struct vchiq_device *
> +vchiq_device_register(struct device *parent, const char *name)
> +{
> + struct vchiq_device *device;
> + int ret;
> +
> + device = kzalloc(sizeof(*device), GFP_KERNEL);
> + if (!device) {
> + dev_err(parent, "Cannot register %s: Insufficient memory\n",
> + name);
AFAIK kzalloc already logs an error in case of insufficient memory, so
there is no need for this.
> + return NULL;
> + }
> +
> + device->dev.init_name = name;
> + device->dev.parent = parent;
> + device->dev.bus = &vchiq_bus_type;
> + device->dev.release = vchiq_device_release;
> +
> + of_dma_configure(&device->dev, parent->of_node, true);
> + ret = dma_set_mask_and_coherent(&device->dev, DMA_BIT_MASK(32));
From my understand Robin suggested to drop dma_set_mask_and_coherent()
here, too. In case this cause a regression until patch 3 & 4 are
applied. The DMA mask parts should be applied separately before this patch.
> + if (ret) {
> + dev_err(&device->dev, "32-bit DMA enable failed\n");
> + return NULL;
> + }
> +
> + ret = device_register(&device->dev);
> + if (ret) {
> + dev_err(parent, "Cannot register %s: %d\n", name, ret);
> + put_device(&device->dev);
Also Robin pointed out that there is a memory leak in the error path,
because the "device" get lost.
Thanks Stefan
> + return NULL;
> + }
> +
> + return device;
> +}
> +
> +void vchiq_device_unregister(struct vchiq_device *vchiq_dev)
> +{
> + device_unregister(&vchiq_dev->dev);
> +}
> +
> +int vchiq_driver_register(struct vchiq_driver *vchiq_drv)
> +{
> + vchiq_drv->driver.bus = &vchiq_bus_type;
> +
> + return driver_register(&vchiq_drv->driver);
> +}
> +EXPORT_SYMBOL_GPL(vchiq_driver_register);
> +
> +void vchiq_driver_unregister(struct vchiq_driver *vchiq_drv)
> +{
> + driver_unregister(&vchiq_drv->driver);
> +}
> +EXPORT_SYMBOL_GPL(vchiq_driver_unregister);
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> new file mode 100644
> index 000000000000..7eaaf9a91cda
> --- /dev/null
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_device.h
> @@ -0,0 +1,54 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2023 Ideas On Board Oy
> + */
> +
> +#ifndef _VCHIQ_DEVICE_H
> +#define _VCHIQ_DEVICE_H
> +
> +#include <linux/device.h>
> +
> +struct vchiq_device {
> + struct device dev;
> +};
> +
> +struct vchiq_driver {
> + int (*probe)(struct vchiq_device *device);
> + void (*remove)(struct vchiq_device *device);
> + int (*resume)(struct vchiq_device *device);
> + int (*suspend)(struct vchiq_device *device,
> + pm_message_t state);
> + struct device_driver driver;
> +};
> +
> +static inline struct vchiq_device *to_vchiq_device(struct device *d)
> +{
> + return container_of(d, struct vchiq_device, dev);
> +}
> +
> +static inline struct vchiq_driver *to_vchiq_driver(struct device_driver *d)
> +{
> + return container_of(d, struct vchiq_driver, driver);
> +}
> +
> +extern struct bus_type vchiq_bus_type;
> +
> +struct vchiq_device *
> +vchiq_device_register(struct device *parent, const char *name);
> +void vchiq_device_unregister(struct vchiq_device *dev);
> +
> +int vchiq_driver_register(struct vchiq_driver *vchiq_drv);
> +void vchiq_driver_unregister(struct vchiq_driver *vchiq_drv);
> +
> +/**
> + * module_vchiq_driver() - Helper macro for registering a vchiq driver
> + * @__vchiq_driver: vchiq driver struct
> + *
> + * Helper macro for vchiq drivers which do not do anything special in
> + * module init/exit. This eliminates a lot of boilerplate. Each module may only
> + * use this macro once, and calling it replaces module_init() and module_exit()
> + */
> +#define module_vchiq_driver(__vchiq_driver) \
> + module_driver(__vchiq_driver, vchiq_driver_register, vchiq_driver_unregister)
> +
> +#endif /* _VCHIQ_DEVICE_H */
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