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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 241A6CA9EBC for ; Sat, 26 Oct 2019 11:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EEDA621655 for ; Sat, 26 Oct 2019 11:07:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=fooishbar-org.20150623.gappssmtp.com header.i=@fooishbar-org.20150623.gappssmtp.com header.b="Yc3V8xSK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726283AbfJZLHT (ORCPT ); Sat, 26 Oct 2019 07:07:19 -0400 Received: from mail-lj1-f196.google.com ([209.85.208.196]:40784 "EHLO mail-lj1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726162AbfJZLHS (ORCPT ); Sat, 26 Oct 2019 07:07:18 -0400 Received: by mail-lj1-f196.google.com with SMTP id u22so6038143lji.7 for ; Sat, 26 Oct 2019 04:07:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fooishbar-org.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sbtSEwwWtUl8Tn9jW/5rYOk9dRDro0TFs9+gAIA3ZLY=; b=Yc3V8xSKcErzzkIufZvgIPdiVXiQAZg6sNPGdV25al2GzTWGRHqUnvyA4S7Ih5edyO yHxfaBIpIxrw9D815r6Jr1Bzx/+i/4rR27vBxJd8iBmgE0hOg3q/326eMB62jlWnaPCa Yfw7O3MR+77F1oM2DJA6ebAdq+4/0esKJnP4U0f9d5mnkKyCWC/WmkmOPoa52YXNbJKq 9iwDZyH0M13Cp5qie3yaDgMbd66uiEv835NGad8aBVbcpOyStYf6yYaUuSgWssFQHW35 rkJuaXJL2r5D0eGpRI7HG+5njgdQJ8tCTye+TfIdiM5yTY6T1DthrJ64fE4/jqnbd2TJ f4yQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sbtSEwwWtUl8Tn9jW/5rYOk9dRDro0TFs9+gAIA3ZLY=; b=p6sgH5FHXFAXFjTXFEUM6nT4EppNJ4UtOHN88j5/vfkUnU48+kiKfrle/1yRUFkt4x H1e+uAZU4tBUqgOrOpOtGJi6JfXbiK4UcU31vyTDxRsr/8Sc0sl7lIbsc++3ol2IDety qHLcu14+6W2l0Kh1WG/+2qvUVj2mqvbrsSh7Py9lFCueNAB+nAt0KU6geLcFJahmt43k iG7dNdNnW9mPSrmQgdtNqpT8fPK4EVfCw5qFWyaKvd0eorbieLueSYu+vmHOLMN5vchx ACuR66Aehcnuw5fSmG0SzJgJ/VdkC4MFgUEHqSe0VkBOk8UUeBUIcBRS90pmZNjEayEJ b6dQ== X-Gm-Message-State: APjAAAUnyrE2os5hcoSY8fERiQnSO+DvGZh81veGM2x9x2EHVEUWEFFM gEbE65m3JYKW02hdCJqr4CFEoX4K2AlAQVZPFEcyCw== X-Google-Smtp-Source: APXvYqwXkiAvXf3Phu3iW0PDFeh83+cl9RW5ZrJMlkjn2TQBbmww5P/ERTPtEJdBkEaAkIJlw1hVNf54K6j0BkUc+Qg= X-Received: by 2002:a2e:8856:: with SMTP id z22mr5727263ljj.78.1572088034673; Sat, 26 Oct 2019 04:07:14 -0700 (PDT) MIME-Version: 1.0 References: <20191023001206.15741-1-rajatja@google.com> <20191024112040.GE2825247@ulmo> <20191025113609.GB928835@ulmo> In-Reply-To: <20191025113609.GB928835@ulmo> From: Daniel Stone Date: Sat, 26 Oct 2019 12:07:00 +0100 Message-ID: Subject: Re: [Intel-gfx] [PATCH] drm: Add support for integrated privacy screens To: Thierry Reding Cc: Rajat Jain , Daniel Vetter , Sean Paul , David Airlie , dri-devel , Rajat Jain , Daniel Thompson , Jonathan Corbet , jsbarnes@google.com, intel-gfx , mathewk@google.com, Maxime Ripard , Duncan Laurie , Greg KH , Linux Kernel Mailing List , Pavel Machek Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thierry, On Fri, 25 Oct 2019 at 12:36, Thierry Reding wrote: > On Thu, Oct 24, 2019 at 01:45:16PM -0700, Rajat Jain wrote: > > I did think about having a state variable in software to get and set > > this. However, I think it is not very far fetched that some platforms > > may have "hardware kill" switches that allow hardware to switch > > privacy-screen on and off directly, in addition to the software > > control that we are implementing. Privacy is a touchy subject in > > enterprise, and anything that reduces the possibility of having any > > inconsistency between software state and hardware state is desirable. > > So in this case, I chose to not have a state in software about this - > > we just report the hardware state everytime we are asked for it. > > So this doesn't really work with atomic KMS, then. The main idea behind > atomic KMS is that you apply a configuration either completely or not at > all. So at least for setting this property you'd have to go through the > state object. > > Now, for reading out the property you might be able to get away with the > above. I'm not sure if that's enough to keep the state up-to-date, > though. Is there some way for a kill switch to trigger an interrupt or > other event of some sort so that the state could be kept up-to-date? > > Daniel (or anyone else), do you know of any precedent for state that > might get modified behind the atomic helpers' back? Seems to me like we > need to find some point where we can actually read back the current > "hardware value" of this privacy screen property and store that back > into the state. Well, apart from connector state, though that isn't really a property as such, there's the link_state property, which is explicitly designed to do just that. That has been quite carefully designed for the back-and-forth though. Cheers, Daniel