Hi Wentong, On Tue, Feb 28, 2023 at 06:35:41AM +0000, Wu, Wentong wrote: > Hi Sakari, > > few questions as switching to v4l2 sub-dev framework. > > > -----Original Message----- > > From: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > > Sent: Wednesday, February 15, 2023 12:06 AM > > > > Hi Wentong, > > > > Thanks for the patchset. > > > > On Mon, Feb 13, 2023 at 10:23:47AM +0800, Wentong Wu wrote: > > > IVSC directly connects to camera sensor on source side, and on output > > > side it not only connects ISH via I2C, but also exposes MIPI CSI-2 > > > interface to output camera sensor data. IVSC can use the camera sensor > > > data to do AI algorithm, and send the results to ISH. On the other > > > end, IVSC can share camera sensor to host by routing the raw camera > > > sensor data to the exposed MIPI CSI-2 interface. But they can not work > > > at the same time, so software APIs are defined to sync the ownership. > > > > > > This commit defines the interfaces between IVSC and camera sensor > > > driver in include/linux/ivsc.h. The camera driver controls ownership > > > of the CSI-2 link and sensor with the acquire/release APIs. When > > > acquiring camera, lane number and link freq are also required by IVSC > > > frame router. > > > > The more I learn about this system, the more I'm inclined to think this > > functionality should be exposed as a V4L2 sub-device. IVSC doesn't really do > > anything to the data (as long as it directs it towards the CSI-2 receiver in the > > SoC), but it is definitely part of the image pipeline. > > > > I suppose the intended use cases assume a single instance of IVSC (as well as > > MEI) but there can, and often are, be multiple camera sensors in the system. The > > decision whether to request pass-through from IVCS can't be done in the camera > > sensor driver, and should not be visible to the camera sensor driver. Exposing > > IVSC as a V4L2 sub-device makes this trivial to address, as the IVSC driver's V4L2 > > sub-device video s_stream() operation gets called before streaming is started. > > > > The information whether IVSC is found between the camera sensor and the > > host's CSI-2 receiver (IPU in this case) should come from system firmware and > > accessed most probably by what is called cio2-bridge at the moment. > > > > The privacy status can be a V4L2 control. > > This should be a control or event? If control, how user-space handle > privacy stuff? Changing control events generates events for the user space. <URL:https://hverkuil.home.xs4all.nl/spec/userspace-api/v4l/dev-event.html> > > For the required link freq and lane number, is v4l2 control the correct > way to configure them? If yes, seems there is no CID value for them so > that we should custom some CID value(link freqm, lane number, and > privacy) for ivsc in linux/v4l2-controls.h, is this acceptable? You should obtain these using the V4L2 fwnode interface. Please see e.g. drivers/media/platform/renesas/rzg2l-cru/rzg2l-csi2.c how that driver registers a V4L2 async sub-device and a V4L2 async notifier. -- Kind regards, Sakari Ailus
