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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 6A5E0C2D0DB for ; Mon, 20 Jan 2020 18:48:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47E9022314 for ; Mon, 20 Jan 2020 18:48:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727071AbgATSsK (ORCPT ); Mon, 20 Jan 2020 13:48:10 -0500 Received: from asavdk3.altibox.net ([109.247.116.14]:40784 "EHLO asavdk3.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726282AbgATSsK (ORCPT ); Mon, 20 Jan 2020 13:48:10 -0500 Received: from ravnborg.org (unknown [158.248.194.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by asavdk3.altibox.net (Postfix) with ESMTPS id 726E220023; Mon, 20 Jan 2020 19:48:06 +0100 (CET) Date: Mon, 20 Jan 2020 19:48:04 +0100 From: Sam Ravnborg To: Geert Uytterhoeven , Paul Cercueil Cc: Noralf T , Greg Kroah-Hartman , Linux Kernel Mailing List , DRI Development Subject: Re: [PATCH v1 2/5] pardata: new bus for parallel data access Message-ID: <20200120184804.GA7630@ravnborg.org> References: <20180802193909.GA11443@ravnborg.org> <20180802194536.10820-2-sam@ravnborg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CMAE-Score: 0 X-CMAE-Analysis: v=2.3 cv=eMA9ckh1 c=1 sm=1 tr=0 a=UWs3HLbX/2nnQ3s7vZ42gw==:117 a=UWs3HLbX/2nnQ3s7vZ42gw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=7gkXJVJtAAAA:8 a=WVoohQUBmtK7-yx5X7kA:9 a=CjuIK1q_8ugA:10 a=E9Po1WZjFZOl8hwRPBS3:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Geert. On Mon, Jan 20, 2020 at 11:10:37AM +0100, Geert Uytterhoeven wrote: > Hi Sam, > > (stumbled on this accidentally) > > On Thu, Aug 2, 2018 at 9:46 PM Sam Ravnborg wrote: > > The pardata supports implement a simple bus for devices > > that are connected using a parallel bus driven by GPIOs. > > The is often used in combination with simple displays > > that is often seen in older embedded designs. > > There is a demand for this support also in the linux > > kernel for HW designs that uses these kind of displays. > > > > The pardata bus uses a platfrom_driver that when probed > > creates devices for all child nodes in the DT, > > which are then supposed to be handled by pardata_drivers. > > > > Signed-off-by: Sam Ravnborg > > > --- /dev/null > > +++ b/Documentation/driver-api/pardata.rst > > @@ -0,0 +1,60 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > + > > +========================= > > +Parallel Data Bus/Drivers > > +========================= > > + > > +Displays may be connected using a simple parallel bus. > > +This is often seen in embedded systems with a simple MCU, but is also > > +used in Linux based systems to a small extent. > > + > > +The bus looks like this: > > + > > +.. code-block:: none > > + > > + ----+ > > + | DB0-DB7 or DB4-DB7 +---- > > + ===/======================== > > + | E - enable | D > > + ---------------------------- I > > + C | Reset | S > > + P ---------------------------- P > > + U | Read/Write (one or two) | L > > + ---------------------------- A > > + | RS - instruction/data | Y > > + ---------------------------- > > + | +---- > > + ----+ > > Oh, cool! Looks like this can be used by the hd44780 driver. > > Documentation/devicetree/bindings/auxdisplay/hit,hd44780.txt > drivers/auxdisplay/hd44780.c This patchset was from a time when I knew next to nothing about DRM. Now I am just confused on a different level :-) It is on my TODO list to make a mipi-dbi driver that in the future replaces the auxdisplay driver for hd44780. But that TODO list have a growing tendency. It seems that pretending to be co-maintainer on panel/ stuff alone can take up most of my DRM time. I hope Paul will contribute the i8080 support to drm_mipi_dbi, at least he mentioned he planned to work on this. Sam