From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 8D7AD7D2EE for ; Thu, 16 Aug 2018 22:00:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725892AbeHQBBc (ORCPT ); Thu, 16 Aug 2018 21:01:32 -0400 Received: from mail-pl0-f66.google.com ([209.85.160.66]:43743 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725903AbeHQBB1 (ORCPT ); Thu, 16 Aug 2018 21:01:27 -0400 Received: by mail-pl0-f66.google.com with SMTP id x6-v6so2718306plv.10 for ; Thu, 16 Aug 2018 15:00:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=w9AkNs0FkR1w/3GFu1Vzzpy+TZydMmyeI+LasrmjPfc=; b=Z6LhTtixqb87OHbshcX9JZKVQnZgm2yJ4tiP0wNeGTXW2sDlWMmoDzc8FsP2wpuiqJ btoRUiun1K0olMWH6NhC+5K8+VfjFeF1ejEewA0ZRhifLy8JsojLgVObdsOkoz8NIXOH 5Ssz7YbLQOysz3AEsEyak1sa9cZsbzOnPKX6+rV7vBO4BYt+L06bSMAPFapcIM3w+48n gm2h9a/LsgfpwYI3lo7iSeOU67puF7Xh0CuPFbT2ATgovg1aqdYQzAR1MZfSPBBOUqpy ALUOv0Pm8nPEXK7u4oF1Rmbu7+IVJgD55u0dvq5x1YHtV3mUkC4oUnur2Wimnh9CjVnU 9sKQ== X-Gm-Message-State: AOUpUlEBsj23Cu4WisGHWMmSJRVAQywJWvv4GqV+KhJ6NkP0YOclX1jM xVj7muXOl5rbv7pQBtttUr4rDQ== X-Google-Smtp-Source: AA+uWPyM2x8smU9jQhf9OiEfn6L5xXsAcMYK7UVzKCsT8H7kcaAf4qdBD1YQQOBH4S15pd0QzzzNRQ== X-Received: by 2002:a17:902:2ac3:: with SMTP id j61-v6mr30294114plb.172.1534456837215; Thu, 16 Aug 2018 15:00:37 -0700 (PDT) Received: from localhost ([207.114.172.147]) by smtp.gmail.com with ESMTPSA id 64-v6sm358841pfi.89.2018.08.16.15.00.36 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 16 Aug 2018 15:00:36 -0700 (PDT) Date: Thu, 16 Aug 2018 15:00:34 -0700 From: Moritz Fischer To: Federico Vaga Cc: Alan Tull , Moritz Fischer , Jonathan Corbet , Randy Dunlap , Dinh Nguyen , Appana Durga Kedareswara Rao , linux-kernel , linux-fpga@vger.kernel.org, Linux Doc Mailing List , Alan Tull , Matthew Gerlach Subject: Re: [PATCH 2/2] fpga: add FPGA manager debugfs Message-ID: <20180816220034.GA4431@archbook> References: <20180815220958.3606-1-atull@kernel.org> <20180816185952.GA3932@archbook> <1841468.1pWPcT6Du7@harkonnen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1841468.1pWPcT6Du7@harkonnen> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Federico, On Thu, Aug 16, 2018 at 11:21:32PM +0200, Federico Vaga wrote: > Hi, > > On Thursday, August 16, 2018 10:04:51 PM CEST Alan Tull wrote: > > On Thu, Aug 16, 2018 at 1:59 PM, Moritz Fischer wrote: > > > Hi Alan, > > > > Hi Moritz, > > > > > comments inline. While I see how this is useful, I have the > > > suspicion that from the moment this gets merged vendor kernels > > > will just default to use this ... > > > > Yeah, I have that suspicion as well. That's probably why I sat on > > this and didn't upstream it for 2 years. But on the other hand, I > > keep hearing of lots of cases of people implementing this > > independently anyway. At least if it is debugfs, it makes it clear > > that it's not intended for production use. > > I'm one of those guys who implemented this independently. We all have in one way or another ;) Most people on ARM run an out of tree patch using devicetree overlays these days I hope rather than /dev/mem and UIO ... or other vender solutions... > > @Mortiz > I do not see how this can be a bad thing (from what you wrote I guess you > prefer another interface). Which interface to use depends on the use case. > If you have this suspicion it's, I guess, because such interface it is > extremely easy to use. What happens to a kernel driver doing MMIO with devices while you reload the entire FPGA from userland? > > @Alan > DebugFS can be a first step, but I would go for a normal device in /dev at > some point. I do not see why this should not be used in production I'm not against having a userland interface to reprogram the FPGA, the Intel DFL code is a good example of a sensible one, doing so in a safe manner. Ideally we'll get around to have a more generic interface, as we get time to work on it. - Moritz