linux-kernel - Re: [PATCH v6 1/8] usb: Add MA-USB Host kernel module

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Date:   Fri, 15 May 2020 15:01:27 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Vladimir Stankovic <vladimir.stankovic@...playlink.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        mausb-host-devel@...playlink.com
Subject: Re: [PATCH v6 1/8] usb: Add MA-USB Host kernel module

On Fri, May 15, 2020 at 02:34:55PM +0200, Vladimir Stankovic wrote:
> --- /dev/null
> +++ b/drivers/usb/host/mausb/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Kernel configuration file for MA-USB Host driver.
> +#
> +# Copyright (c) 2019 - 2020 DisplayLink (UK) Ltd.
> +#
> +
> +config USB_HOST_MAUSB
> +	tristate "Media Agnostic (MA) USB Host Driver"
> +	depends on USB=y

Why =y?  That should not be a requirement for any usb host driver.

> +	help
> +	  This is a Media Agnostic (MA) USB Host driver which enables host
> +	  communication via MA USB protocol stack.
> +
> +	  If this driver is compiled as a module, it will be named mausb_host.

Provide links to the userspace and spec here so that people have a
chance to be able to use this driver?



> diff --git a/drivers/usb/host/mausb/Makefile b/drivers/usb/host/mausb/Makefile
> new file mode 100644
> index 000000000000..cafccac0edba
> --- /dev/null
> +++ b/drivers/usb/host/mausb/Makefile
> @@ -0,0 +1,10 @@
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Makefile for DisplayLink MA-USB Host driver.
> +#
> +# Copyright (c) 2019 - 2020 DisplayLink (UK) Ltd.
> +#
> +
> +obj-$(CONFIG_USB_HOST_MAUSB) += mausb_host.o
> +mausb_host-y := mausb_core.o
> +mausb_host-y += utils.o
> diff --git a/drivers/usb/host/mausb/mausb_core.c b/drivers/usb/host/mausb/mausb_core.c
> new file mode 100644
> index 000000000000..44f76a1b74de
> --- /dev/null
> +++ b/drivers/usb/host/mausb/mausb_core.c
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019 - 2020 DisplayLink (UK) Ltd.
> + */
> +#include <linux/module.h>
> +
> +#include "utils.h"
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("DisplayLink (UK) Ltd.");
> +
> +static int mausb_host_init(void)
> +{
> +	return mausb_host_dev_register();
> +}
> +
> +static void mausb_host_exit(void)
> +{
> +	dev_info(mausb_host_dev.this_device, "Module unloading started...");
> +	mausb_host_dev_deregister();
> +}
> +
> +module_init(mausb_host_init);
> +module_exit(mausb_host_exit);
> diff --git a/drivers/usb/host/mausb/utils.c b/drivers/usb/host/mausb/utils.c
> new file mode 100644
> index 000000000000..1cfa2140311e
> --- /dev/null
> +++ b/drivers/usb/host/mausb/utils.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2019 - 2020 DisplayLink (UK) Ltd.
> + */
> +#include "utils.h"
> +
> +#include <linux/fs.h>
> +#include <linux/slab.h>
> +
> +#define MAUSB_KERNEL_DEV_NAME "mausb_host"
> +#define MAUSB_READ_DEVICE_TIMEOUT_MS 500
> +
> +struct miscdevice mausb_host_dev;
> +
> +static int mausb_host_dev_open(struct inode *inode, struct file *filp)
> +{
> +	filp->private_data = NULL;
> +
> +	return 0;
> +}
> +
> +static int mausb_host_dev_release(struct inode *inode, struct file *filp)
> +{
> +	kfree(filp->private_data);
> +	filp->private_data = NULL;
> +
> +	return 0;
> +}
> +
> +static const struct file_operations mausb_host_dev_fops = {
> +	.open	 = mausb_host_dev_open,
> +	.release = mausb_host_dev_release,
> +};
> +
> +int mausb_host_dev_register(void)
> +{
> +	mausb_host_dev.minor = MISC_DYNAMIC_MINOR;
> +	mausb_host_dev.name = MAUSB_KERNEL_DEV_NAME;
> +	mausb_host_dev.fops = &mausb_host_dev_fops;
> +	mausb_host_dev.mode = 0;

You only have 1 device in the system at a time?  With a global
structure?  And no locking at all?

That feels _very_ wrong, why?

And mode of 0?  You don't want any userspace code to use this device
node?

confused,

greg k-h