From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A974718BBAE; Thu, 23 Apr 2026 13:37:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776951427; cv=none; b=ae1qqdWJoSDBRnUNzT7hV71KKczsNG5yWRD8rpFqmQep8+eH7K+mkvR1UzVd2TymEZCf+kezLOo62vQNQmx/brzcTqgR/fm6fVRI55kvPBOjx4EVV+40hu5mweon3NFq6Xc+OxJHjGGuxJLuLesp0Kh2SqPSoO/+WgjfoZd3RLQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776951427; c=relaxed/simple; bh=SCMeXc6iNHZVhRhU78udGlaYW9NkW14onQYu/AiF6M4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=T7LdzhQcL3vN43mHa1BoCZis0uXlR8COTZmcAtYZDemq7IDHjdf8EjI7VSMfPXZh56mFhS/nJxIKFA6J2z+Y6VCYKusJ07gy9lWC1WmGPFUCuUyBhrM5J7pYto1AvtQqSe/FMWKojNoTSpcFqXHx7Wpa1oDk7NIwgXic+rLEWfc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=au64Nxy3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="au64Nxy3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEA45C2BCAF; Thu, 23 Apr 2026 13:37:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776951427; bh=SCMeXc6iNHZVhRhU78udGlaYW9NkW14onQYu/AiF6M4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=au64Nxy3WFohQJGnz3FSUq8C7RO3sPhLi5iwbU952kiR0Ope5w7kJ7cYGLG4z5SMC e/VFjhoABO6Y7Anyln2loRbXXujZZXjWCvV/JbnsUf8poq5HkVfBCsog9kgnuwaH8M BBlgRx59Y7oEpJWqqpEH2KOrwWDxjL8NrCi1uVSs= Date: Thu, 23 Apr 2026 15:37:04 +0200 From: Greg Kroah-Hartman To: Vishnu Reddy Cc: Bryan O'Donoghue , Vikash Garodia , Dikshita Agarwal , Abhinav Kumar , Mauro Carvalho Chehab , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Joerg Roedel , Will Deacon , Robin Murphy , Bjorn Andersson , Konrad Dybcio , Stefan Schmidt , Hans Verkuil , "Rafael J. Wysocki" , Danilo Krummrich , Thierry Reding , Mikko Perttunen , David Airlie , Simona Vetter , Jonathan Hunter , linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, driver-core@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, Ekansh Gupta , Dmitry Baryshkov Subject: Re: [PATCH v2 02/13] drivers: base: Add generic dma context bus Message-ID: <2026042346-trustable-register-095a@gregkh> References: <20260423-glymur-v2-0-0296bccb9f4e@oss.qualcomm.com> <20260423-glymur-v2-2-0296bccb9f4e@oss.qualcomm.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20260423-glymur-v2-2-0296bccb9f4e@oss.qualcomm.com> On Thu, Apr 23, 2026 at 06:59:31PM +0530, Vishnu Reddy wrote: > From: Ekansh Gupta > > When a driver needs to create virtual device at runtime and map it to > an IOMMU context for memory isolation, there is no common bus available > for this purpose. Each driver ends up implementing its own bus type, > leading to duplicated logic across multiple drivers. > > host1x driver implemented its own bus type to attach an IOMMU context to > a dynamically created device. The Iris VPU driver now has the same > requirement. Rather than duplicating the same bus logic again, a shared > bus type is introduced under drivers/base that multiple drivers can use > directly. > > The bus takes care of creating a device and attaching the IOMMU context > to it based on the client inputs. > > Suggested-by: Dmitry Baryshkov > Signed-off-by: Ekansh Gupta > Signed-off-by: Vikash Garodia > Signed-off-by: Vishnu Reddy > --- > drivers/base/Kconfig | 3 ++ > drivers/base/Makefile | 1 + > drivers/base/dma_context_bus.c | 77 +++++++++++++++++++++++++++++++++++++++++ > include/linux/dma_context_bus.h | 26 ++++++++++++++ > 4 files changed, 107 insertions(+) as you can not have a device on multiple busses at the same time, this makes no sense to me at all. "dma context" is a bus-specific thing, so please add it to the bus that you are wanting it for. It can't be a generic bus as that just doesn't work. Or what am I missing here? And why is DMA somehow "special" here from any other hardware attribute? thanks, greg k-h