Hi folks, This preliminary RFC patchset prepares for the request API. What's new here is support for binding arbitrary configuration or resources to requests. There are a few new concepts here: Class --- a type of configuration or resource a driver (or e.g. the V4L2 framework) can attach to a resource. E.g. a video buffer queue would be a class. Object --- an instance of the class. This may be either configuration (in which case the setting will stay until changed, e.g. V4L2 format on a video node) or a resource (such as a video buffer). Reference --- a reference to an object. If a configuration is not changed in a request, instead of allocating a new object, a reference to an existing object is used. This saves time and memory. I expect Laurent to comment on aligning the concept names between the request API and DRM. As far as I understand, the respective DRM names would be "object" and "state". The drivers will need to interact with the requests in three ways: - Allocate new configurations or resources. Drivers are free to store their own data into request objects as well. These callbacks are specific to classes. - Validate and queue callbacks. These callbacks are used to try requests (validate only) as well as queue them (validate and queue). These callbacks are media device wide, at least for now. The lifetime of the objects related to requests is based on refcounting both requests and request objects. This fits well for existing use cases whether or not based on refcounting; what still needs most of the attention is likely that the number of gets and puts matches once the object is no longer needed. Configuration can be bound to the request the usual way (V4L2 IOCTLs with the request_fd field set to the request). Once queued, request completion is signalled through polling the request file handle (POLLPRI). I'm posting this as an RFC because it's not complete yet; I'll continue working on it next week. Todo list: - Better separation of request support between media-device.c and media-request.c. The intent is that mostly IOCTL handling would be in media-device.c. - Request support in a few drivers as well as the control framework. - Request support for V4L2 formats. - Provide means to iterate over references in a request. This would be useful for drivers. The exact needs will be clearer once support for a few drivers has been added. - Reinit support. In the future, support for changing e.g. Media controller link state or V4L2 sub-device formats will need to be added. Those are not in my immediate plans though. Comments and questions are welcome. Open questions: - How to tell at complete time whether a request failed? Return error code on release? What's the behaviour with reinit then --- fail on error? Add another request command to ask for status? Alexandre Courbot (1): videodev2.h: add request_fd field to v4l2_ext_controls Hans Verkuil (1): videodev2.h: Add request_fd field to v4l2_buffer Laurent Pinchart (1): media: Add request API Sakari Ailus (5): media: Support variable size IOCTL arguments media: Support polling for completed requests media: Add support for request classes and objects staging: media: atomisp: Remove v4l2_buffer.reserved2 field hack vb2: Add support for requests drivers/media/Makefile | 3 +- drivers/media/common/videobuf2/videobuf2-core.c | 43 +- drivers/media/common/videobuf2/videobuf2-v4l2.c | 24 +- drivers/media/media-device.c | 483 ++++++++++++++++++++- drivers/media/media-request.c | 287 ++++++++++++ drivers/media/usb/cpia2/cpia2_v4l.c | 2 +- drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 16 +- drivers/media/v4l2-core/v4l2-ioctl.c | 6 +- .../media/atomisp/pci/atomisp2/atomisp_ioctl.c | 17 +- include/media/media-device.h | 80 +++- include/media/media-request.h | 229 ++++++++++ include/media/videobuf2-core.h | 19 + include/media/videobuf2-v4l2.h | 2 + include/uapi/linux/media.h | 10 + include/uapi/linux/videodev2.h | 6 +- 15 files changed, 1186 insertions(+), 41 deletions(-) create mode 100644 drivers/media/media-request.c create mode 100644 include/media/media-request.h -- 2.7.4
