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[91.145.109.188]) by smtp.gmail.com with ESMTPSA id d33-20020a0565123d2100b0044a0c8e0625sm71857lfv.290.2022.03.17.19.34.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Mar 2022 19:34:21 -0700 (PDT) Message-ID: <10fb1261-f22f-8e21-4056-166c283e26f2@redhat.com> Date: Fri, 18 Mar 2022 04:34:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v2] mm/hmm/test: simplify hmm test code: use miscdevice instead of char dev To: Jason Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, apopple@nvidia.com, jhubbard@nvidia.com, rcampbell@nvidia.com, vbabka@suse.cz 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> From: =?UTF-8?Q?Mika_Penttil=c3=a4?= In-Reply-To: <20220317141539.GD64706@ziepe.ca> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: CB0BAC0030 X-Stat-Signature: rmobiaricwj8foffhrff3xsmx8im5sfy Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Rpt6DhFH; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf28.hostedemail.com: domain of mpenttil@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=mpenttil@redhat.com X-Rspam-User: X-HE-Tag: 1647570865-358996 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 17.3.2022 16.15, Jason Gunthorpe wrote: > On Thu, Mar 17, 2022 at 08:58:52AM +0200, Mika Penttil=C3=A4 wrote: >> @@ -1225,7 +1232,11 @@ static int dmirror_device_init(struct dmirror_d= evice >> *mdevice, int id) >> >> cdev_init(&mdevice->cdevice, &dmirror_fops); >> mdevice->cdevice.owner =3D THIS_MODULE; >> - ret =3D cdev_add(&mdevice->cdevice, dev, 1); >> + device_initialize(&mdevice->device); >> + dev_set_name(&mdevice->device, "%s", dmirror_device_names[id])= ; >> + mdevice->device.devt =3D dev; >> + >> + ret =3D cdev_device_add(&mdevice->cdevice, &mdevice->device); >> if (ret) >> return ret; >=20 > Right, miscdev isn't that helpful in the end.. >=20 > Jason >=20 To wrap up, I could send a v3 formal patch with either this cdev way or=20 the miscdev way.. Both eliminate the user space /proc/devices parsing=20 and mknod'ing. Jason brought up concerns using miscdevice like this,=20 although for this case it works correctly. miscdevice also provides a=20 little more cleanup and simpler code, but the difference is not huge. So=20 what do people prefer? Thanks, Mika