linux-kernel - Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev

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Message-ID: <20220318124011.GE64706@ziepe.ca>
Date:   Fri, 18 Mar 2022 09:40:11 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Mika Penttilä <mpenttil@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        apopple@...dia.com, rcampbell@...dia.com, vbabka@...e.cz
Subject: Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice
 instead of char dev

On Thu, Mar 17, 2022 at 07:58:25PM -0700, John Hubbard wrote:
> In other words, given that the usage here is correct, is there some
> reason that miscdevice is still a poor design fit? Is cdev_device_add()
> a better choice here, for design reasons?

cdev's have become so easy to use I don't see the few loc reduction to
add miscdev that valuable. IMHO

> Also, is there any change that could or should be made to miscdevice,
> that you have in mind?

No, it is just a legacy interface that was simplifies drivers that
create a single char dev in static data that is widely misused.

IOW I wouldn't add new miscdevs.

Jason