> -----Original Message----- > From: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > Sent: Tuesday, February 28, 2023 4:24 PM > > 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> Ok, V4L2_EVENT_CTRL event which reports 'struct v4l2_event_ctrl' data to user space > > > > > 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. Ok, something like v4l2_ctrl_find(source->ctrl_handler, V4L2_CID_LINK_FREQ); is to get sensor's link frequency, and the code like 'v4l2_subdev_call(source, pad, get_mbus_config, source, &mbus_config); num_of_lanes = mbus_config.bus.mipi_csi2.num_data_lanes;' is to get sensor's lane number. BR, Wentong > > -- > Kind regards, > > Sakari Ailus
