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 89C7F175A6D; Sun, 5 Apr 2026 20:15:52 +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=1775420152; cv=none; b=RutOlaYDxw4VhP+hHy4nMG7fTka4cpOCV2B47oxfnRCM7IFS9BMveyy0Zj8peHw6VmZzO7OBN/Jcz5X8blXPIV6cJG7I/2GW1fb1RyDjspIQOJ/wo+KiddeuYQELWV9H0BjJmObf0z6ZLRKx6XKcZo9NL2/Za3c4PC4YTR9VrdI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775420152; c=relaxed/simple; bh=WPnZeRoYPMD7LQArMyMpA3mzTez1znm9JptH71Egp1A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JiyFTxc1mKgClO0riVJpVc9At/5c/wdgL68W8ffBnpMgjX8QpT9qUNc2vFbN0LJ4V/+mGb5ubTxSeCYO2xVUS6vriTHPf0rYnhorxKuBR60YzzugPkUBNiH0RI/q3mslm8b1tlBPqgPmg2lv9DsauIlLCAw9V486h+MDnXy4tQ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MCsZmn74; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MCsZmn74" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62F46C116C6; Sun, 5 Apr 2026 20:15:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775420152; bh=WPnZeRoYPMD7LQArMyMpA3mzTez1znm9JptH71Egp1A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MCsZmn74CksgapuNoLZ4UnANnnD87QpD9QEfo2k4aGjnrDVtwhWrHxqk5sUWCM3Ej uTnc5Ck1HEAChPIepf1mgKaD1Cr8d2DWhNePuIpJPcgO/PgnB6ZxjN8Yz7/QTs3mt6 nnyMNOrXZacS2Wfi7RYRbtnVZvm/RWq+QoSL4OdEzhV+VJdy4dQ1W0VZh0BAJ3gZn+ 12TjizJQiZaRSyBc2i9f4j4BWgFW4+lENxVlROyYRHlLYumdj4zHudMsdbWZsnvqkG VtH5Qb1fVS+F+lZofv7XAIPW53ebQ8KPK+rlYCUDn0t7iP6yVbRkbaEJnrWVQG6Uit P3kI7/0EXK2Ag== Message-ID: <3bcd8500-ff6c-4a1f-8b7e-3e7c474f6345@kernel.org> Date: Sun, 5 Apr 2026 21:15:47 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/3] media: qcom: camss: Add CAMSS Offline Processing Engine driver To: Laurent Pinchart Cc: Loic Poulain , vladimir.zapolskiy@linaro.org, kieran.bingham@ideasonboard.com, robh@kernel.org, krzk+dt@kernel.org, andersson@kernel.org, konradybcio@kernel.org, linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, johannes.goede@oss.qualcomm.com, mchehab@kernel.org References: <20260323125824.211615-1-loic.poulain@oss.qualcomm.com> <20260323125824.211615-3-loic.poulain@oss.qualcomm.com> <1ba54ec0-be51-4694-a79b-f272e76303d2@kernel.org> <12194cc0-0960-486c-be7e-1a22d95de340@kernel.org> <20260405201129.GB1213462@killaraus.ideasonboard.com> Content-Language: en-US From: Bryan O'Donoghue In-Reply-To: <20260405201129.GB1213462@killaraus.ideasonboard.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 05/04/2026 21:11, Laurent Pinchart wrote: > The mali-c55 driver does this, it translates the ISP parameters buffers > to a list of register values in userspace context, when the buffer is > queued. In the IRQ handler, it then either copies those values to > registers with MMIO writes, or use a DMA engine, depending on the > platform. The rppx1 driver does something similar, with a different > format for the buffer containing the register values. > > I think this architecture could be replicated here. This translation in > userspace context ensures that work at IRQ time is limited. The driver > can use whatever DMA engine is available depending on the platform, and > we can also force usage of MMIO for debugging or development purpose. > That way, development of ISP features is decoupled from development of > CDM support, enabling parallel development if desired, and faster > plaform enablement that allows starting the userspace side of the work > quicker. I think that's a reasonable plan. We make the buffer in user-space which could be used by CDM but stage the implementation. That way if CDM proves too hard, we can do MMIO for a while, and then transition to CDM if/when. For me though I really think translating between formats is storing up pain. --- bod