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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E7E17CA5FA2 for ; Mon, 28 Sep 2026 16:40:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:In-Reply-To:References:Cc:To:Subject: From:MIME-Version:Date:Message-ID:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=FZUYNBRcOcwahT/HwUn9HlQGjcQyMs/osOqncN2KOUo=; b=GvM2i+URcs3PMzWI322oBRB4+s SQrhf6CC8ZAmJkvSvV8t3yLLDIfc0GZ9Kj2R0mlhyF9kuRJctdwKp0RHDWu5+3gvibfRvxskVGmx5 qyHAYJUZNQRxwe0PguhjeuFPP5GfbIdXwQ+FZNeg4V3Tg0JKe76WsK9pgqEMFrJupeNnmkyJVWNvF zHBbzcKBN4/yfguu0/wT48OMgjv4xARMCXVl2aOGGmD5M2NgfDu/EmBHmDrbrNeH+a0WXBNjTB/5N kGWtWcDMamYYjubeIsRf+SCc4Bz2HNG5cnXjPM8dOIdAoDVzgjIMrrBkXZIXG5UK9QfEyAfUzu1fF 8ae0/X+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBEOi-000000013Yx-29xk; Mon, 28 Sep 2026 16:40:12 +0000 Received: from mail-wm2-x10.google.com ([2a00:1450:4864:31::10]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBEOe-000000013Xo-3wOo for linux-arm-kernel@lists.infradead.org; Mon, 28 Sep 2026 16:40:10 +0000 Received: by mail-wm2-x10.google.com with SMTP id 5b1f17b1804b1-49b912e4b11so18737925e9.3 for ; Mon, 28 Sep 2026 09:40:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1790613606; x=1791218406; darn=lists.infradead.org; h=content-transfer-encoding:content-type:in-reply-to:organization :autocrypt:content-language:references:cc:to:subject:reply-to:from :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to:content-type; bh=FZUYNBRcOcwahT/HwUn9HlQGjcQyMs/osOqncN2KOUo=; b=ELwrn2tTFuycPtIFgvSvM9QkUeTj3dHitfblnHpfqDDqed3NE9jAJPd1L/ujcx4uao a/cCfLcKNyZBavZrOS6rJ/+OsKQ1EuNsv8VTXNFpecHQILOIkqB+iICVw4z5zhqJBLQq tPBByYRk3SeGpofsMWu+1IPFQjzjt+xG3ICoRTLki1SgW+fBPyDneTHuU6ucz0mztpqe IVczxyJ9jRMSXeEGodgzIxolicSqg9CC27Jd1eEgmarsIq8r/WxmO+qWLETYBLZQTL9B dTPsOCWxxPxT/5Z8Vyovlo+kU5oEkeOQg8LK2YZsdQ7By7kNK5afxE3ryOvAxk80FK2w qMAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790613606; x=1791218406; h=content-transfer-encoding:content-type:in-reply-to:organization :autocrypt:content-language:references:cc:to:subject:reply-to:from :user-agent:mime-version:date:message-id:x-gm-gg:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to:content-type; bh=FZUYNBRcOcwahT/HwUn9HlQGjcQyMs/osOqncN2KOUo=; b=ktNKHQBAOyKRpZ0juSk6U/c+skMgW+nVsYOV8Xf9Au+H1ODgPTwS4Rq+mnz/LxH3ja XK+jiBshfTGGBDw6/MXMvGDlGopdXzJcgA8OkN5yiibBLG5HnVqwRLLELt7B0VHpckt/ Np6kGMUMvly++XDO+JKPyPBizCS4w2uehfZ3Rl4hCayVAttPIhotV5QGCTeUt3LxAjiw Pi56CniBNsloeLy2QNzGlBykkhfjO+Fbakk4YUlIAkobGhxJNUpGWHsjO6eI5QJOG+2g vXe5bBrJ9mM6tSajBlXRaeF20X0nwzprYqkyIKngIl7DTaeO6GMut+Us/CgmUvdOFisg M0mw== X-Forwarded-Encrypted: i=1; AKwUvBwAQC8KQtGWsnTGSoanK0xQSYk/3ZvKFeXS2rn2yNphgGuVF8enyi4xSGSj1fY32f5fyouAxiXMpNMhgakMDgn7@lists.infradead.org X-Gm-Message-State: AFuF++kHfax5CcxH72njFSF1s1jwUFOBtNqP4Afwuukao7XwSK0Fm7hp 3QmDnuZpxNtEKcjqskxdoSqVUOsmylIWaB8dnn1Bx77caP7cEufEIc4a8uylCKTOG/E= X-Gm-Gg: AYBFou32zcpADx+rGw9XhWG1kTY4czjMJwZ5c/E9OMuur/bGla9hxZN9hwV5kr3ZbPV jTNAGlFisjrcLBbyoU6zMHnYPiPzBn+rr5JLHFmArSUI63/oHinSD10XgA5ZAkQ979DxInt7Njp 6l5dxX230xCGxI6CXCy5sP8c5hcWynqYeDCZP05kaRswI8dS9GlMa5K/OvakHV4rWp26nB4QOw4 8hZYjfh7ykkttRWV/e0Pjk+Xk/sjfa2b9wbQWrf/GniNJGu/zZ3CDc5ukTeU9jR9PqKYaZdAM0P Ixiq0SZulOEUK04VREg1juWCbK84uyPlFIdgGtC4O5fXyzjZ2IxJLErri/OfCHfeSWDWSFnoTxq mgz6W7cOP20DXoQ2Si7oDvGOCmelCp+LWJ4i8x3fVYUqulxvXKKGFWzPIi3w/EuMkXwnSwrFvWM 3H6Eb04l9+c72mIT4kKNyZXo5OcrcuJ7v8hyHOutQErHK7xv77wmURgUwscCHL41WRBwQAwebUp cMK9UNKLQ16UVgR1qimjOXgU/JenrlQ5m8JtJSMNHWHIE4= X-Received: by 2002:a05:600c:4e12:b0:49c:fc6e:a3df with SMTP id 5b1f17b1804b1-49fe66f82d8mr225035645e9.30.1790613606106; Mon, 28 Sep 2026 09:40:06 -0700 (PDT) Received: from [192.168.27.65] (82-64-67-166.subs.proxad.net. [82.64.67.166]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a00d0ea071sm3637265e9.9.2026.09.28.09.40.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Sep 2026 09:40:05 -0700 (PDT) Message-ID: <6b80cb97-6706-412a-b013-9423f6f75153@linaro.org> Date: Mon, 28 Sep 2026 18:39:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Subject: Re: [PATCH 0/6] drm/bridge: Add a BPF-based MIPI-DSI panel driver To: Maxime Ripard , Jessica Zhang , David Airlie , Simona Vetter , Maarten Lankhorst , Thomas Zimmermann , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Florian Fainelli , Broadcom internal kernel review list Cc: Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Albert Esteve , Dave Stevenson , Javier Martinez Canillas , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Benjamin Tissoires References: <20260928-drm-mipi-dsi-panel-ebpf-v1-0-5244926aace4@kernel.org> Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: <20260928-drm-mipi-dsi-panel-ebpf-v1-0-5244926aace4@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260928_094009_035264_4E232E00 X-CRM114-Status: GOOD ( 38.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Neil Armstrong Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 9/28/26 18:22, Maxime Ripard wrote: > Hi, > > Panels in general, and MIPI-DSI panels in particular, are pretty > difficult to support and require pretty much a panel driver for each > panel produced. Most of them are pretty simple, and require an opaque > initialization sequence that is usually poorly documented. > > This creates a tension between OEMs and distros because OEMs will > typically get a new panel to react to a sourcing issue during > production, and thus need some swift turnaround between getting their > new panel and it being operational in the OS. Distributions on the other > hand can take years to ship a kernel with that new panel driver. > > To solve this, I followed the example of HID-BPF and wrote a panel > driver that will rely on BPF programs to perform the panel > initialization. That way, we can ship the programs separately from the > kernel, and with a different lifecycle. If this driver is accepted, the > plan is to have a userspace component started by udev to identify and > load the right BPF program for the panels found on the device. This is kind of late for serious applications except if we manage to solve the bootloader to Linux display engine transition. > > This driver is fully functional and works with both 5" and 7" Touch > Display 2 panels for the RaspberryPi. However, it breaks away from the > typical panel driver in multiple ways: > > - BPF programs can only be loaded by userspace. This leaves us with two > choices: > > * We prevent the driver from loading until the script itself is > loaded. This has the side effect of preventing any other output to > be used until the initramfs is ran at the earliest, and possibly > ever if the loader isn't installed for example. This adds a dependency on user-space behavior and if somehow the initramfs doesn't load for a reason we won't have a way to display an error. > > * Or we probe the driver all the time, but only report it as connected > once a program has been registered. This is somewhat unconventional, > but allows the other outputs to be functional, *and* allows the user > to force the output if their panel doesn't require any > initialization or during debugging. I chose this solution. Both options are not really great... > > - It's not a panel driver, but a bridge one, which is also pretty > unconventional. This is required because panel drivers don't have > access to a detect callback that is required for the above, but I also > think that the recent work from Luca blurs the line from panels and > bridges and we'll end up going that road anyway. On this point, DDIC _are_ bridges, but in the current panel API we blur the line between the panel and the DDIC. So being a bridge is fine, but in a general way we lack a proper way to describe the display/panel/monitor independently of the DDIC. At first glance it's a nice driver, but moving the timings into a blob moves something into possible proprietary binaries with possible closed licence and distribution restriction so it's a downgrade for the same of bringing up a panel faster. I'll review further and comment. > > Let me know what you think, > Maxime > > Signed-off-by: Maxime Ripard > --- > Maxime Ripard (6): > dt-bindings: display: Add panel-mipi-dsi-bpf generic panel binding > drm/panel: Add generic MIPI-DSI panel driver with BPF init sequences > drm/panel: dsi-bpf: Add BPF program build infrastructure and helper header > drm/panel: dsi-bpf: Add Raspberry Pi 7-inch panel BPF program > drm/panel: dsi-bpf: Add Raspberry Pi 5-inch panel BPF program > [DO NOT MERGE] arm64: dts: broadcom: Add Raspberry Pi ILI9881C DSI panel overlays > > .../bindings/display/panel/panel-mipi-dsi-bpf.yaml | 184 +++++++++ > arch/arm64/boot/dts/broadcom/Makefile | 8 + > .../bcm2711-rpi-4-b-dsi-ili9881-5inch.dtso | 22 + > .../bcm2711-rpi-4-b-dsi-ili9881-7inch.dtso | 22 + > .../dts/broadcom/bcm2711-rpi-4-b-dsi-ili9881.dtsi | 65 +++ > drivers/gpu/drm/panel/Kconfig | 3 + > drivers/gpu/drm/panel/Makefile | 1 + > drivers/gpu/drm/panel/bpf/Kconfig | 28 ++ > drivers/gpu/drm/panel/bpf/Makefile | 10 + > .../gpu/drm/panel/bpf/panel-bpf-mipi-dsi-core.c | 452 +++++++++++++++++++++ > .../gpu/drm/panel/bpf/panel-bpf-mipi-dsi-kfuncs.c | 278 +++++++++++++ > drivers/gpu/drm/panel/bpf/panel-bpf-mipi-dsi-ops.c | 242 +++++++++++ > .../gpu/drm/panel/bpf/panel-bpf-mipi-dsi-trace.c | 4 + > .../gpu/drm/panel/bpf/panel-bpf-mipi-dsi-trace.h | 246 +++++++++++ > drivers/gpu/drm/panel/bpf/panel-bpf-mipi-dsi.h | 264 ++++++++++++ > drivers/gpu/drm/panel/bpf/progs/Makefile | 93 +++++ > .../panel/bpf/progs/Raspberrypi__dsi-5inch.bpf.c | 266 ++++++++++++ > .../panel/bpf/progs/Raspberrypi__dsi-7inch.bpf.c | 271 ++++++++++++ > .../gpu/drm/panel/bpf/progs/panel-bpf-mipi-dsi.h | 95 +++++ > 19 files changed, 2554 insertions(+) > --- > base-commit: 6e375de99d0c420169481fcd36064177ab55b09d > change-id: 20260928-drm-mipi-dsi-panel-ebpf-d78b72a9c47f > > Best regards,