Hi Wentong, On Mon, Feb 20, 2023 at 03:50:55AM +0000, Wu, Wentong wrote: > > > > -----Original Message----- > > From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > > Sent: Friday, February 17, 2023 7:19 PM > > > > Hi Wentong, > > > > On Fri, Feb 17, 2023 at 06:10:22AM +0000, Wu, Wentong wrote: > > > On Sent: Wednesday, February 15, 2023 5:46 PM, Laurent Pinchart wrote: > > > > On Wed, Feb 15, 2023 at 10:03:29AM +0100, Hans de Goede wrote: > > > > > On 2/14/23 17:06, Sakari Ailus wrote: > > > > > > 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. > > > > > > > > > > Yes I happened to discuss this exact same thing with Laurent at > > > > > FOSDEM and we also came to the conclusion that the IVSC chip > > > > > should be modeled as a V4L2 sub-device. > > > > > > > > Agreed. > > > > > > Thanks for your quick review and conclusion, I'm fresh to media > > > sub-system, is there any convention that I should follow to upstream > > > this kind of v4l2 sub-device driver so that not too much back and > > > forth? > > > > This is a tentative proposal, as I'm not very familiar with the hardware > > architecture: > > > > - The subdev should have two pads, a sink pad connected to the camera > > sensor, and a source pad connected to the CSI-2 receiver in the IPU. > > > > - As for any new driver, the subdev driver should use the active state > > managed by the v4l2-subdev core. This requires calling > > v4l2_subdev_init_finalize() at probe time. See > > https://git.linuxtv.org/media_tree.git/commit/?id=a2514b9a634a for an > > example of a subdev driver converted to this mechanism. > > > > - As we're talking about CSI-2, the subdev driver should use the streams > > API that was recently merged, and in particular support the > > .get_frame_desc(), .set_routing(), .enable_streams() and > > .disable_streams() operations. > > > > - I don't see a need to support V4L2 controls in the subdev driver, but > > I may be missing something. > > > > - The driver should be validated with v4l2-compliance, part of > > v4l-utils. > > > > Thanks for the detail, but I have one more question, during probe of > sensor(v4l2-sudev) driver, it will configure camera sensor connected to > IVSC via I2C, but before that it should acquire camera sensor's ownership > from IVSC, how v4l2 framework guarantee this? Please wrap the lines at 74 characters or so when replying. Do you mean accessing the sensor via I²C also requires acquiring the sensor from IVSC? -- Regards, Sakari Ailus
