From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0167A377018; Thu, 1 Oct 2026 06:50:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790837445; cv=none; b=pJ0MewdUdWTDLgl0qtPSSF2021vFYp18aWM+vbZMVsha7XPHNR7ppJUl9Ce1babzdROArW1VITadA5C+u2eHyWe70mIJd7+igpu0SQYAGGFdCeT170swzjvFjhcpesRdiwWtioM+j/P/pEuavwS2Da1aiktjDRhYQTP686SFv3Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790837445; c=relaxed/simple; bh=WrUdE2khAdlf1/MsWrHbA7qdAiwyidVJ+i8uJKDW1Wk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tKmo09oZwkBjr0t0N2EXRtJzS4MxL9t0hl51h1MGdsIpfMnByqIx+XV5vEEOGsrr0U5iUujTCcpJUI46xW4xtCJIHL6vw+cNHcfKXZ5x7aVN7SLECrdpFkGRhej7uBOm1lnBhgOKVZjx/jabac/YhDn4s6lL9FOYe2PZyur8MAs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q/e1gTPS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q/e1gTPS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 020551F000FF; Thu, 1 Oct 2026 06:50:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790837443; bh=WrUdE2khAdlf1/MsWrHbA7qdAiwyidVJ+i8uJKDW1Wk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Q/e1gTPSrCSD68j7AaM7kzhCj2ouy4/v4QCOpa4HPL95utDNjJDwaZcZ5yGt5FqHT dD9PdDvoB5wopVPaRUq1UAeYloJJeguRywdsCqjCiiKB5cxWI4vPLwYkY7+3LZtATD KmVg3PbwmG1y5oDsWEQPpIJPN2OQb+UI+VrOfR3kxc8KHogXvmB8fJraf4V0sqQ2Oz vAgJ6b627+BtkKxmUT/wjiJH6AUNYmTPfdyuQSm0oPlybPjUoP725ioqJLOgWUMbq7 tEA/EsJoAied51k1DcbyvxC6A3+5Qr44rstP7rVsk6lSHACIUtf8vJgXinZravVGlZ cvLpKC2jfGAfg== Date: Thu, 1 Oct 2026 08:50:40 +0200 From: Maxime Ripard To: Neil Armstrong Cc: Javier Martinez Canillas , Benjamin Tissoires , 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 , Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Albert Esteve , Dave Stevenson , 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 Subject: Re: [PATCH 0/6] drm/bridge: Add a BPF-based MIPI-DSI panel driver Message-ID: References: <20260928-drm-mipi-dsi-panel-ebpf-v1-0-5244926aace4@kernel.org> <6b80cb97-6706-412a-b013-9423f6f75153@linaro.org> <0259fe4b-3118-4ab0-9b62-55101bfd7f33@linaro.org> <674314b4-6b80-4b3a-ac15-eefd31cea607@linaro.org> <828c9108-2db1-45a6-9301-19159a094301@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha384; protocol="application/pgp-signature"; boundary="kw273bz54geum3wd" Content-Disposition: inline In-Reply-To: <828c9108-2db1-45a6-9301-19159a094301@linaro.org> --kw273bz54geum3wd Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 0/6] drm/bridge: Add a BPF-based MIPI-DSI panel driver MIME-Version: 1.0 On Wed, Sep 30, 2026 at 03:37:58PM +0200, Neil Armstrong wrote: > On 9/29/26 09:55, Javier Martinez Canillas wrote: > > Maxime Ripard writes: > >=20 > > > On Mon, Sep 28, 2026 at 10:36:18PM +0200, Neil Armstrong wrote: > > > > On 9/28/26 21:48, Benjamin Tissoires wrote: > > > > > On Sep 28 2026, Neil Armstrong wrote: > > > > > > On 9/28/26 19:24, Benjamin Tissoires wrote: > > > > > > > On Sep 28 2026, Neil Armstrong wrote: > > > > > > > > Hi, > > > > > > > >=20 > > > > > > > > On 9/28/26 18:22, Maxime Ripard wrote: > > > > > > > > > Hi, > > > > > > > > >=20 > > > > > > > > > Panels in general, and MIPI-DSI panels in particular, are= pretty > > > > > > > > > difficult to support and require pretty much a panel driv= er for each > > > > > > > > > panel produced. Most of them are pretty simple, and requi= re an opaque > > > > > > > > > initialization sequence that is usually poorly documented. > > > > > > > > >=20 > > > > > > > > > This creates a tension between OEMs and distros because O= EMs will > > > > > > > > > typically get a new panel to react to a sourcing issue du= ring > > > > > > > > > production, and thus need some swift turnaround between g= etting their > > > > > > > > > new panel and it being operational in the OS. Distributio= ns on the other > > > > > > > > > hand can take years to ship a kernel with that new panel = driver. > > > > > > > > >=20 > > > > > > > > > To solve this, I followed the example of HID-BPF and wrot= e a panel > > > > > > > > > driver that will rely on BPF programs to perform the panel > > > > > > > > > initialization. That way, we can ship the programs separa= tely 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 de= vice. > > > > > > > >=20 > > > > > > > > This is kind of late for serious applications except if we = manage to > > > > > > > > solve the bootloader to Linux display engine transition. > > > > > > > >=20 > >=20 > > Besides what Maxime already mentioned (that most general purpose Linux = distributions > > built the drivers as modules anyways), it doesn't have to be mutually e= xclusive. > >=20 > > A simple panel could be supported using this BPF-based driver and then = a panel driver > > added to the kernel, if is found that some applications need to have it= built-in and > > earlier in the boot path. > >=20 > > I don't see why this would be any different than HDI-BPF or other BPF-b= ased infra, > > such as sched_ext. > > I don't want to add a supplementary maintenance burden for the sake of us= ing a cool > technology which has serious drawbacks and dependencies on user-space eve= n if looks > really cool. Spoiler alert: v2 won't. I've got the in-kernel loader to work and thus you can have a built-in panel driver that works without user-space intervention. So this is not a topic of discussion anymore. Maxime will work --kw273bz54geum3wd Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJUEABMJAB0WIQTkHFbLp4ejekA/qfgnX84Zoj2+dgUCar4CvwAKCRAnX84Zoj2+ dvcSAX49Wfvd2Nx91Qlv77RICWSMxTGFolQVADy53gvu7ebfWo/lEDg2wmMLUV5U MkA52hMBgIONoBjDpHdMNV7byAvh44CSyrq8DcktEoCEF8a0dOoxQJ5lKBLZgdH2 o+5/ElvokQ== =5iv0 -----END PGP SIGNATURE----- --kw273bz54geum3wd--