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[142.162.113.129]) by smtp.gmail.com with ESMTPSA id s21-20020a05620a16b500b0067b1205878esm3687255qkj.7.2022.03.18.05.40.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Mar 2022 05:40:12 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1nVBts-002PWG-0b; Fri, 18 Mar 2022 09:40:12 -0300 Date: Fri, 18 Mar 2022 09:40:11 -0300 From: Jason Gunthorpe To: John Hubbard Cc: Mika =?utf-8?B?UGVudHRpbMOk?= , linux-kernel@vger.kernel.org, linux-mm@kvack.org, apopple@nvidia.com, rcampbell@nvidia.com, vbabka@suse.cz Subject: Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev Message-ID: <20220318124011.GE64706@ziepe.ca> References: <20220311033050.22724-1-mpenttil@redhat.com> <20220314182439.GB64706@ziepe.ca> <20220315183922.GC64706@ziepe.ca> <8e836d75-97b0-d301-4d6a-92025e91cad5@redhat.com> <0f53c5ff-1711-861d-9a12-0634d4ab9fca@redhat.com> <20220317141539.GD64706@ziepe.ca> <10fb1261-f22f-8e21-4056-166c283e26f2@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: oqqnno6mj3x8bibhs8m67odt4butpbgt Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=ziepe.ca header.s=google header.b=N8mXUAv1; spf=pass (imf16.hostedemail.com: domain of jgg@ziepe.ca designates 209.85.219.46 as permitted sender) smtp.mailfrom=jgg@ziepe.ca; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 93F94180023 X-HE-Tag: 1647607214-935911 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000066, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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