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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C13AC021BB for ; Mon, 24 Feb 2025 14:57:46 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 843E08930B; Mon, 24 Feb 2025 14:57:45 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="Mh7TFlCr"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.11]) by gabe.freedesktop.org (Postfix) with ESMTPS id 031FF8930B for ; Mon, 24 Feb 2025 14:57:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1740409065; x=1771945065; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=ApbmW1BVLLWh9Y/yw3zWhdEJQrg5lHizqsSsqNz41bs=; b=Mh7TFlCraqWktYWmeqI9Svia61tunJ0vKV7ckH8pmf85GAecOgN3T9lP RfIMJXmv78nyxNYNMb6LcWilzRan4J3O/p3nVKRr0zYR3mnP1pnJlv6tG wNwA/60HX9GKO0fLgQpwGnM/alJNSjTcYeT9y1li4Ya9Lm0C6As3LlFLt G5sSyOd/N1yqOCo9tMPJas+1OsWubcQ6ZcUtgurkyDq8+L9kIEmFhQdAm TyD01NXmtEnxOOqB0As37GoKJzCq0RGqF14GC97kd3G2F1izGMPCIzW3e 85bK8BhCOgYMMO2q64rkbrx6dk0fAuvGOCwS5+uFdpmC4CF2vq8wEcOq8 w==; X-CSE-ConnectionGUID: giz6chAzQ72zK0KhX3kWTQ== X-CSE-MsgGUID: OSFK6nwuQ5S1x/vB94V/0g== X-IronPort-AV: E=McAfee;i="6700,10204,11355"; a="51380521" X-IronPort-AV: E=Sophos;i="6.13,309,1732608000"; d="scan'208";a="51380521" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Feb 2025 06:57:45 -0800 X-CSE-ConnectionGUID: fj4upMoLRuGZSzt6VUfMXA== X-CSE-MsgGUID: GM9+VcLkSF+/Kc2LOMAWLA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,309,1732608000"; d="scan'208";a="115814785" Received: from smile.fi.intel.com ([10.237.72.58]) by orviesa009.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Feb 2025 06:57:42 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.98) (envelope-from ) id 1tmZtq-0000000Ej0X-2boH; Mon, 24 Feb 2025 16:57:38 +0200 Date: Mon, 24 Feb 2025 16:57:38 +0200 From: "andriy.shevchenko@linux.intel.com" To: Aditya Garg Cc: "maarten.lankhorst@linux.intel.com" , "mripard@kernel.org" , "tzimmermann@suse.de" , "airlied@gmail.com" , "simona@ffwll.ch" , Kerem Karabay , Atharva Tiwari , Aun-Ali Zaidi , Linux Kernel Mailing List , "dri-devel@lists.freedesktop.org" Subject: Re: [PATCH v4 2/2] drm/tiny: add driver for Apple Touch Bars in x86 Macs Message-ID: References: <844C1D39-4891-4DC2-8458-F46FA1B59FA0@live.com> <5BC3A795-99C2-4F00-ADD0-7ECD0285CDD0@live.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5BC3A795-99C2-4F00-ADD0-7ECD0285CDD0@live.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Feb 24, 2025 at 02:32:37PM +0000, Aditya Garg wrote: > > On 24 Feb 2025, at 7:30 PM, andriy.shevchenko@linux.intel.com wrote: > > On Mon, Feb 24, 2025 at 01:40:20PM +0000, Aditya Garg wrote: ... > >> +#define __APPLETBDRM_MSG_STR4(str4) ((__le32 __force)((str4[0] << 24) | (str4[1] << 16) | (str4[2] << 8) | str4[3])) > > > > As commented previously this is quite strange what's going on with endianess in > > this driver. Especially the above weirdness when get_unaligned_be32() is being > > open coded and force-cast to __le32. > > I would assume it was also mimicked from the Windows driver, though I haven't > really tried exploring this there. > > I’d rather be happy if you give me code change suggestions and let me review > and test them For the starter I would do the following for all related constants and drop that weird and ugly macros at the top (it also has an issue with the str4 length as it is 5 bytes long, not 4, btw): #define APPLETBDRM_MSG_CLEAR_DISPLAY cpu_to_le32(0x434c5244) /* CLRD */ ... (assuming we stick with __leXX for now). This will be much less confusing. ... > >> +struct appletbdrm_msg_information { > >> + struct appletbdrm_msg_response_header header; > >> + u8 unk_14[12]; > >> + __le32 width; > >> + __le32 height; > >> + u8 bits_per_pixel; > >> + __le32 bytes_per_row; > >> + __le32 orientation; > >> + __le32 bitmap_info; > >> + __le32 pixel_format; > >> + __le32 width_inches; /* floating point */ > >> + __le32 height_inches; /* floating point */ > >> +} __packed; > > > > Haven't looked deeply into the protocol, but still makes me think that > > the above (since it's the only __packed data type required) might be simply > > depicted wrongly w.r.t. endianess / data types in use. It might be that > > the data types have something combined and / or different types. > > > > Do I understand correctly that the protocol was basically reverse-engineered? > > Yes. Although it was reverse engineered by the person who wrote the Windows > driver. The author has just made a Linux port. > So, as far as how is was reverse engineered, it not really possible for me to > explain. I don't even have any contact with the person who wrote the Windows > driver. The only point here would be to myself RE the hardware again, which > tbh isn't very motivating, considering that we have a working driver. Right. I agree that is better to have something working than something good looking, but wrong. Can you add a summary to the commit message that since the driver was reverse-engineered the actual data types of the protocol might be different (including, but not limited to, endianess)? ... > >> + /* > >> + * The coordinate system used by the device is different from the > >> + * coordinate system of the framebuffer in that the x and y axes are > >> + * swapped, and that the y axis is inverted; so what the device reports > >> + * as the height is actually the width of the framebuffer and vice > >> + * versa > > > > Missing period. > > Alright. For some reason (a mistake on my part), some dev_err_probe were also > still left in this version. But those are seems to me in the correct locations, no? How do we even know the DRM device before its creation? So, dev_err_probe() calls in ->probe() seem logical to me. Somebody from DRM should clarify this. > >> + */ ... > I’ll send a v5. Please, wait a bit. it's too fast to send one version quicker than 24h... -- With Best Regards, Andy Shevchenko