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Thanks for you quick reply. > > On Wed, Jun 17, 2026 at 03:50:12PM -0400, Frank.Li@oss.nxp.com wrote: > > From: Frank Li > > > > Many V4L2 subdev drivers implement the same registration and media pad > > setup logic for simple pipelines consisting of a single sink pad and a > > single source pad. As a result, the same boilerplate code is duplicated > > across multiple drivers. > > > > Introduce a common helper library for 1-to-1 subdevs to encapsulate the > > registration, media entity initialization, and cleanup paths. Drivers > > can embed a struct v4l2_subdev_1to1 instance and use the provided helper > > APIs instead of open-coding the setup sequence. > > I appreciate your efforts in trying to reduce the amount of code drivers > need simply to get things done but I think there are a few issues with the > approach taken in this patch: > > - The new helpers aren't generic enough, but require two pads; one sink, > one source. It can cover many case already, there are many bridge type subdev. after glace of all code, many CSI2RX is type device. It should one kind important type/case, like sensors. And I plan do 1 TO N replicator driver, which duplicate 1 sink pad to N source pad (with/without register config), plus exist video-mux driver, It think It can cover more than 80% cases. > You could provide special helpers for just this case, but > right now it looks like that if there's something you need that the > helper assumes you don't, you can't use the helper at all. In other > words, more modularity would be nice. We can add it later if need, which easy to replace 1to1 API, like I did for sensor one. > > - The new helper should work with the existing types and not add new types > (struct v4l2_subdev_1to1). May be save vep data into v4l2_subdev to avoid parse it every time. and enhence media_entity_pads_init() to avoid refer caller data. > > - There should be a way to provide default V4L2 fwnode endpoint > configuration as well as to validate the obtained configuration. Do you means remote_bustype_cap_mask information get from a callback? > > I don't have a good proposal to address the above but at least one way I > can think of making error handling easier would be to use devm_() for > teardown in more places we to today. That certainly does have its own > issues though. I tried it before, media and v4l2's clean up is not revised order of init. Sorry, I can't find original thread. I remember laurnet pinchart said there are order problem. 1 v4l2_subdev_init() 2. v4l2_async_subdev_nf_init() 3. v4l2_async_nf_register() 4. media_entity_pads_init() 5 v4l2_async_register_subdev() v4l2_async_unregister_subdev(sd); v4l2_subdev_cleanup(sd); // Not sure if it save to move to last step media_entity_cleanup(&sd->entity); v4l2_async_nf_unregister(&csi2->notifier); v4l2_async_nf_cleanup(&csi2->notifier); Frank > > -- > Kind regards, > > Sakari Ailus