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Date:   Wed, 20 Jan 2021 19:46:09 +0000
From:   Christoph Hellwig <hch@infradead.org>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     gregkh@linuxfoundation.org, logang@deltatee.com,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Alexandre Belloni <alexandre.belloni@free-electrons.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org
Subject: Re: [PATCH 1/3] cdev: Finish the cdev api with queued mode support
Message-ID: <20210120194609.GA3843758@infradead.org>
References: <161117153248.2853729.2452425259045172318.stgit@dwillia2-desk3.amr.corp.intel.com>
 <161117153776.2853729.6944617921517514510.stgit@dwillia2-desk3.amr.corp.intel.com>
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The subject doesn't make any sense to me.

But thn again queued sound really weird.  You just have a managed
API with a refcount and synchronization, right?

procfs and debugfs already support these kind of managed ops, kinda sad
to duplicate this concept yet another time.

> +static long cdev_queued_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

Overly long line.

> +__must_check int __cdev_register_queued(struct cdev *cdev, struct module *owner,
> +					dev_t dev, unsigned count,
> +					const struct cdev_operations *qops)
> +{
> +	int rc;
> +
> +	if (!qops->ioctl || !owner)
> +		return -EINVAL;

Why is the ioctl method mandatory?