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[23.128.96.18]) by mx.google.com with ESMTP id y12si8803367jai.84.2021.08.15.05.32.48; Sun, 15 Aug 2021 05:33:00 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@denx.de header.s=phobos-20191101 header.b=RU1j9tOF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235540AbhHOMcM (ORCPT + 99 others); Sun, 15 Aug 2021 08:32:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231809AbhHOMcM (ORCPT ); Sun, 15 Aug 2021 08:32:12 -0400 Received: from phobos.denx.de (phobos.denx.de [IPv6:2a01:238:438b:c500:173d:9f52:ddab:ee01]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9A3BC061764 for ; Sun, 15 Aug 2021 05:31:41 -0700 (PDT) Received: from [127.0.0.1] (p578adb1c.dip0.t-ipconnect.de [87.138.219.28]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: marex@denx.de) by phobos.denx.de (Postfix) with ESMTPSA id B95F980661; Sun, 15 Aug 2021 14:31:37 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=denx.de; s=phobos-20191101; t=1629030698; bh=nQY6qqdT6huVToGeMTGVRdsLDdRQvPBapmnRWJDxrts=; h=Subject:To:References:From:Date:In-Reply-To:From; b=RU1j9tOFbT4v0es7JJsrpsjGP24guhL+lFpp0jXf884nwY2A+ZWA6x1jU7ImskAyS T08wcKxuXfivJpQlZ5Icx8dUte2j09TATb7ZxVUgKsAQr7ioCPUMsvEx5MXZIXIE1m UhJCG2xTDao5iSPGV8e/B22Lz5oNXRF0WktNGgFnMJL/CNFmojJ/yp8uiG/31+lWi+ 8LcMUN17oP9pLeDQHD7pUXa57dmfF+luSsXxpSR+/fFpea8FiAtwyOBDT4vfsLMBvj 0rDqMVhsDmNdlPqwtNyNI2exqt+DAk5RXxneenQRZAGYtVKBYViNXGYEuUPZZlE9NJ Lrw/jgB+UG8PA== Subject: Re: Revert "video: fbdev: mxsfb: Remove driver" To: Alistair Francis , Fabio Estevam , Shawn Guo , Sascha Hauer , dl-linux-imx , b.zolnierkie@samsung.com, Linux Kernel Mailing List , Alistair Francis , Sam Ravnborg References: From: Marek Vasut Message-ID: Date: Sun, 15 Aug 2021 14:31:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Virus-Scanned: clamav-milter 0.103.2 at phobos.denx.de X-Virus-Status: Clean Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/15/21 2:16 PM, Alistair Francis wrote: > Hello, > > Commit f225f1393f034 "video: fbdev: mxsfb: Remove driver" removed the > mxsfb fbdev driver. > > I am now working on getting mainline Linux running on the reMarkable 2 > eInk reader [1]. Unfortunately the rM2 doesn't use the standard EPD > controller on the i.MX SoC, but instead uses the LCD controller. > > eInk panels are complex to control and require writing temperature > dependent waveforms. As these waveforms are proprietary [2] the rM > team runs closed source software called SWTCON in userspace to control > the panel [3]. > > This closed source software expects the fbdev mxsfb driver and it > doesn't work with the DRM mxsfb driver (at least not that I can get it > to). > > The NXP fork of Linux also re-adds the fbdev driver [4], so they also > see some uses for it. > > I was wondering if the community would be open to re-adding the fbdev > mxsfb driver to mainline? It could be re-added with a different > dt-binding so that it is not used by default and only enabled for > boards when required (like for the rM2). > > 1: https://remarkable.com/store/remarkable-2 > 2: https://goodereader.com/blog/e-paper/e-ink-waveforms-are-a-closely-guarded-secret > 3: https://remarkablewiki.com/tech/rm2_framebuffer > 4: https://source.codeaurora.org/external/imx/linux-imx/log/drivers/video/fbdev/mxsfb.c?h=lf-5.10.35-2.0.0 +CC Sam. What sort of special thing does your proprietary userspace do that cannot be added to the DRM driver or the fbdev emulation (if needed) ?