Hi Laurent, Laurent Pinchart wrote: > Hi Oleksiy, > > Thank you for the patch. > > [CC'ing linux-media] > > On Sunday 03 June 2012 19:17:06 Oleksij Rempel wrote: >> Hi Laurent, >> >> in attachment is a suggestion patch for media framework and a test >> program which use this patch. >> >> Suddenly we still didn't solved the problem with finding of XU. You >> know, the proper way to find them is guid (i do not need to explain this >> :)). Since uvc devices starting to have more and complicated XUs, media >> api is probably proper way to go - how you suggested. >> >> On the wiki of TexasInstruments i found some code examples, how they use >> this api. And it looks like there is some desing differences between >> OMPA drivers and UVC. It is easy to find proper entity name for omap >> devices just by: "(!strcmp(entity[index].name, "OMAP3 ISP CCDC"))". >> We can't do the same for UVC, current names are just "Extension %u". We >> can put guid instead, but it will looks ugly and not really informative. >> This is why i added new struct uvc_ext. >> >> If you do not agree with this patch, it will be good if you proved other >> solution. This problem need to be solved. > > The patch goes in the right direction, in that I think the media controller > API is the proper way to solve this problem. However, extending the > media_entity_desc structure with information about all possible kinds of > entities will not scale, especially given that an entity may need to expose > information related to multiple types (for instance an XU need to expose its > GUID, but also subdev-related information if it has a device node). > > I've been thinking about adding a new ioctl to the media controller API for > some time now, to report advanced static information about entities. > > The idea is that each entity would be allowed to report an arbitrary number > of > static items. Items would have a type (for which we would likely need some > kind of central registry, possible with driver-specific types), a length and > data. The items would be static (registered an initialization time) and > aggregated in a single buffer that would be read in one go through a new > ioctl. > > One important benefit of such an API would be to be able to report more than > one entity type per subdev using entity type items. Many entities serve > several purpose, for instance a sensor can integrate a flash controller. This > can't be reported with the current API, as subdevs have a single type. By > having several entity type items we could fix this issue.
I welcome this idea! Another example of information that's missing currently is the lack of bus information for the entities: it's next to impossible for the user space to learn which i2c device a subdev is related to. At the same time we could deprecate the media_entity_desc.type field. Providing entity bus information as part of entity enumeration would resolve this issue. Btw. do you think a new IOCTL is really required? Why not to just add a pointer for additional data the user may provide to the driver to fill up? There's plenty of room in the struct for a pointer and perhaps a size field. Cheers, -- Sakari Ailus sakari.ai...@iki.fi -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
