From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay3-d.mail.gandi.net (relay3-d.mail.gandi.net [217.70.183.195]) (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 9EDC4293B7A; Mon, 14 Apr 2025 11:52:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744631561; cv=none; b=YPCOxKmRADKZeN3XPkRpRhBSsa77me8udoUT16M5OUo25EQ0khg5PykS1qbiN8gNwfjwG/rQM0L0RcAN3PDyXmY2aPWO3AS+4Cs39macttB9v4+B+3GCzC8aRwXlS6JGj6PBKp6mnhMQ/KCOu5tMa+jS0DdWsGad0Vg0Adm18aE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744631561; c=relaxed/simple; bh=O7fwWD1mrXhcYE+62v3u8tACzz3xgehepQ421SFC7Y4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=uav0O1drH2tkzKf7uin8BL80c3FJ+FHegdqWb7c0Kuz7DT1lu7w3hduq3B4jz6Qo1fAvTBavNOEB/OYJH9zkVCs/z+4D7KdM+wUurwZUPvnQTjhhwpprXWvxAeDfhYYIIbiZEgpywnZGVi6xAzDW94eruQ31wOnS99LVsQAnrUE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=IhGYi+h7; arc=none smtp.client-ip=217.70.183.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="IhGYi+h7" Received: by mail.gandi.net (Postfix) with ESMTPSA id 8FFE91FCE8; Mon, 14 Apr 2025 11:52:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1744631551; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=O7fwWD1mrXhcYE+62v3u8tACzz3xgehepQ421SFC7Y4=; b=IhGYi+h78AvbQGLD5cEOJulxIDP+2+4l3nLgXrIGuxmV9DsjjL+7P340iwkXJSV2LUV7s4 THBdzmeFxAxisAiks8R2gwmyUqgB0BhN/Q2+9xb1u/UIC4a6sVgDua9OjJPr7PEVRRrPzE EOw7dha9QqISuFU89I981uZaI8/YnLtAScOsAzcPDenHsWofgNSyRcERL9EwI8icCeVx4A oU9/uF4aKTrzuvOWxiah8ItsZLI4AjH26n/gm4N10FqxvhiW9COuZ9TpL9Q6JG//LVuPkh zJFRriURbRjyzsUfjkkRQ/VFT3bZtAZtTrhjQ/QN9Z4/FGZoIuL2HsfKUNBoTQ== Date: Mon, 14 Apr 2025 13:52:28 +0200 From: Thomas Petazzoni To: Christian =?UTF-8?B?S8O2bmln?= Cc: Christoph Hellwig , Bastien Curutchet , Sumit Semwal , Greg Kroah-Hartman , linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] uio/dma-buf: Give UIO users access to DMA addresses. Message-ID: <20250414135228.600c13e6@windsurf> In-Reply-To: <29eb3698-7dc2-4c32-b636-8ef0ee6d1f47@amd.com> References: <20250410-uio-dma-v1-0-6468ace2c786@bootlin.com> <20250414102455.03331c0f@windsurf> <29eb3698-7dc2-4c32-b636-8ef0ee6d1f47@amd.com> Organization: Bootlin X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-GND-State: clean X-GND-Score: -100 X-GND-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddvvddtgeekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuifetpfffkfdpucggtfgfnhhsuhgsshgtrhhisggvnecuuegrihhlohhuthemuceftddunecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvvefukfgjfhhoofggtgfgsehtqhertdertdejnecuhfhrohhmpefvhhhomhgrshcurfgvthgriiiiohhnihcuoehthhhomhgrshdrphgvthgriiiiohhnihessghoohhtlhhinhdrtghomheqnecuggftrfgrthhtvghrnhepheduteeufeekieevieegueegiefgvdevhefggfdutdeiuedvtdfgledvgeevleeinecuffhomhgrihhnpegsohhothhlihhnrdgtohhmnecukfhppedvrgdtvdemkeegfeegmeelfhdtleemvdektddumeefsgelmeejsggtfhemheehleehmegvfhefvgenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpedvrgdtvdemkeegfeegmeelfhdtleemvdektddumeefsgelmeejsggtfhemheehleehmegvfhefvgdphhgvlhhopeifihhnughsuhhrfhdpmhgrihhlfhhrohhmpehthhhomhgrshdrphgvthgriiiiohhnihessghoohhtlhhinhdrtghomhdpnhgspghrtghpthhtohepledprhgtphhtthhopegthhhrihhsthhirghnrdhkohgvnhhighesrghmugdrtghomhdprhgtphhtthhopehhtghhsehinhhfrhgruggvrggurdhorhhgpdhrtghpthhtohepsggrshhtihgvn hdrtghurhhuthgthhgvthessghoohhtlhhinhdrtghomhdprhgtphhtthhopehsuhhmihhtrdhsvghmfigrlheslhhinhgrrhhordhorhhgpdhrtghpthhtohepghhrvghgkhhhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhgpdhrtghpthhtoheplhhinhhugidqmhgvughirgesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtthhopegurhhiqdguvghvvghlsehlihhsthhsrdhfrhgvvgguvghskhhtohhprdhorhhgpdhrtghpthhtoheplhhinhgrrhhoqdhmmhdqshhigheslhhishhtshdrlhhinhgrrhhordhorhhg X-GND-Sasl: thomas.petazzoni@bootlin.com Hello Christian, On Mon, 14 Apr 2025 11:11:48 +0200 Christian K=C3=B6nig wrote: > Maybe I should try to better explain the concern here. The question > is "Where is the source code of your FPGA driver?". >=20 > I mean that you are trying to replace the out-of-tree solution is > rather welcomed, but the out-of-tree solutions are out-of-tree > because they don't fit with requirements to be added to the core > Linux tree. >=20 > And one of those requirements is that you need to provide the source > code of the userspace user of this interface, in this case here that > is your FPGA driver. An MIT/X11 license is usually sufficient, GPL is > of course seen as better and it must not be a toy application, but > rather the real thing. Where is this requirement for UIO? The UIO subsystem does not have such a requirement, unlike indeed some other kernel subsystems such as DRM. But the practical situation is different: for DRM it makes a lot of sense to enforce having open-source code in user-space, as we want to force GPU vendors to open their OpenGL/Vulkan implementations. However, for UIO it makes little sense, because UIO is typically used to control some super-specific FPGA IP blocks that are totally irrelevant outside of the very specific product they are included in. Most likely if those drivers were open-sourced and tried to be upstream they would be rejected because their usefulness in the upstream kernel is basically zero (but they would have an on-going maintenance effort for the whole community). > And that is what people usually don't want and that's why no in-tree > solution exists for this. And that doesn't make sense because UIO already exists, and allows to achieve 95% of what people already need, to the exception of this DMA issue. Thomas --=20 Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com