From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5739BC433FE for ; Fri, 18 Mar 2022 12:40:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236350AbiCRMlf (ORCPT ); Fri, 18 Mar 2022 08:41:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230008AbiCRMld (ORCPT ); Fri, 18 Mar 2022 08:41:33 -0400 Received: from mail-qv1-xf2e.google.com (mail-qv1-xf2e.google.com [IPv6:2607:f8b0:4864:20::f2e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AAAA318FAD8 for ; Fri, 18 Mar 2022 05:40:14 -0700 (PDT) Received: by mail-qv1-xf2e.google.com with SMTP id kj11so2481594qvb.11 for ; Fri, 18 Mar 2022 05:40:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=LmXFCGzUKyPQi78MWhxrBmfo7hI3p1k1nGlp0osF6aE=; b=N8mXUAv1YJYYXpNEDsy6vW/WLv9Vz81haAY4pqjnXzeeSVmCtQCzHqfHXmv5cIM2xM rAvax9y02XCxJsRtzNdXXerS+FAZvFY/QwUHYliHtOK+PqFozR/5QqTof2faIsUyoOBC dg9L4PF4Y+16G/ezIbymndqaF+X6NdRG4Oyqq/x0TYK34hMr+bV0QnSruVcIX64h4ViU qTvNW5CDzRdn9NQohU4HXVLCUlCMfGJYlSv0c5oUrltNEFYHXwWOk1opkQFmvaAzi2mf /legt+wKJmBn1rN3IkGMvuYcvuc353y2NaJPES5jXrh/42mWCcyZI29dv7TswLIHO0JD 95eg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=LmXFCGzUKyPQi78MWhxrBmfo7hI3p1k1nGlp0osF6aE=; b=ps+/NcS/vydyeN3fdgoadndSq9ZKplKhHb2LewFAIPohikVG8fKfpMoXy3J2W7mcom Ff2MeF7LjJksER3G95pwMguxX7OM3D49rzM4Eq2IGpxAOQ1x4w+vmn4oNWF82CIjzzTy yNlrF/VmTFEwXAbjtnzTS2gDFSlIU0dLle92FZVqnz+SJuh5YwbeT5p80OaiQS+AT5qX sPNo4Wroabn5wuXwX1LFctQh89S8+m2Fd8kbOGB3fxU4BfedFNNy0vu2SRuHoyFhO0ro HH5fRbOoIe2moAkTujBxtwPO+WvbN3BCeIH+kzK//iMex3vDMe4oZj10NnTplhhXIvgk 3cdQ== X-Gm-Message-State: AOAM531/O6vljiXUWEArDi42B2W95jVecLqVxJiOenHq1nyhg64HXO2w 8owrhq/xf7SLo4LTtt5BrVOBHA== X-Google-Smtp-Source: ABdhPJzmR2mz++JSeS3jA3a1AzaNng4Z1ET3mUDT9Wsi+KzkjLdBsOxJfgKV5E03f9dBkHx7OhnM4A== X-Received: by 2002:a05:6214:3016:b0:439:365c:56b6 with SMTP id ke22-20020a056214301600b00439365c56b6mr6819937qvb.47.1647607213824; Fri, 18 Mar 2022 05:40:13 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [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: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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