From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp.nokia.com ([147.243.1.48]:20993 "EHLO mgw-sa02.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753295Ab2BRCVG (ORCPT ); Fri, 17 Feb 2012 21:21:06 -0500 Message-ID: <4F3F0AFE.8050705@iki.fi> Date: Sat, 18 Feb 2012 04:20:46 +0200 From: Sakari Ailus MIME-Version: 1.0 To: Laurent Pinchart CC: Sylwester Nawrocki , Sylwester Nawrocki , linux-media@vger.kernel.org, g.liakhovetski@gmx.de, m.szyprowski@samsung.com, riverful.kim@samsung.com, sw0312.kim@samsung.com, Kyungmin Park Subject: Re: [RFC/PATCH 3/6] V4L: Add g_embedded_data subdev callback References: <1329416639-19454-1-git-send-email-s.nawrocki@samsung.com> <6366737.ZEMB1VQOcD@avalon> <4F3EE3C3.6070605@gmail.com> <4603092.UUnjJ05PXI@avalon> In-Reply-To: <4603092.UUnjJ05PXI@avalon> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi Laurent, Laurent Pinchart wrote: > On Saturday 18 February 2012 00:33:23 Sylwester Nawrocki wrote: >> On 02/18/2012 12:23 AM, Laurent Pinchart wrote: >>>> struct v4l2_subdev_video_ops { >>>> >>>> int (*s_routing)(struct v4l2_subdev *sd, u32 input, u32 output, u32 >>>> >>>> config); @@ -321,6 +329,8 @@ struct v4l2_subdev_video_ops { >>>> >>>> struct v4l2_mbus_config *cfg); >>>> >>>> int (*s_mbus_config)(struct v4l2_subdev *sd, >>>> >>>> const struct v4l2_mbus_config *cfg); >>>> >>>> + int (*g_embedded_data)(struct v4l2_subdev *sd, unsigned int *size, >>>> + void **buf); >>>> >>>> }; >>> >>> How is the embedded data transferred from the sensor to the host in your >>> case ? Over I2C ? >> >> It's transferred over MIPI-CSI2 bus and is intercepted by the MIPI-CSI2 >> receiver, before the image data DMA. The MIPI-CSI2 doesn't have its own >> DMA engine. More details can be found in patch 6/6. > > As the data is transmitted by the device without any polling from the host, > shouldn't it just go to a metadata plane in the V4L2 buffer ? I'd say that if it can be given to the user space separately, a way should be provided to do that. It's all about timing: software controlled digital camera depend on that. Some receivers are also able to put such metadata into a separate memory area using DMA, such as the OMAP 3 ISP CCP-2 receiver. Cheers, -- Sakari Ailus sakari.ailus@iki.fi