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 for "class" and "object" used in this set 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. The code compiles but no testing has been done yet. Todo list: - Testing! (And fixing the bugs.) - Request support in a few drivers as well as the control framework. - Request support for V4L2 formats? In the future, support for changing e.g. Media controller link state or V4L2 sub-device formats will need to be added. Those should receive more attention when the core is in a good shape and the more simple use cases are already functional. Comments and questions are welcome. since v1: - Provide an iterator helper for request objects in a request. - Remove the request lists in the media device (they were not used) - Move request queing to request fd and add reinit (Alexandre's patchset); this roughly corresponds to Request API RFC v2 from Hans. (MEDIA_IOC_REQUEST_ALLOC argument is a struct pointer instead of an __s32 pointer.) - Provide a way to unbind request objects from an unqueued request (reinit, closing request fd). - v4l2-mem2mem + vivid implementation without control support. - More states for requests. In order to take a spinlock (or a mutex) for an extended period of time, add a "QUEUEING" and "REINIT" states. - Move non-IOCTL code to media-request.c, remove extra filp argument that was added in v1. - SPDX license header, other small changes. 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 IOCTL to ask for completion 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 (7): media: Support variable size IOCTL arguments staging: media: atomisp: Remove v4l2_buffer.reserved2 field hack vb2: Add support for requests v4l: m2m: Simplify exiting the function in v4l2_m2m_try_schedule v4l: m2m: Support requests with video buffers vim2m: Register V4L2 video device after V4L2 mem2mem init vim2m: Request support drivers/media/Makefile | 3 +- drivers/media/common/videobuf2/videobuf2-core.c | 43 +- drivers/media/common/videobuf2/videobuf2-v4l2.c | 40 +- drivers/media/media-device.c | 80 ++- drivers/media/media-request.c | 650 +++++++++++++++++++++ drivers/media/platform/vim2m.c | 76 ++- 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 +- drivers/media/v4l2-core/v4l2-mem2mem.c | 131 ++++- .../media/atomisp/pci/atomisp2/atomisp_ioctl.c | 17 +- include/media/media-device.h | 19 +- include/media/media-request.h | 301 ++++++++++ include/media/v4l2-mem2mem.h | 28 + include/media/videobuf2-core.h | 19 + include/media/videobuf2-v4l2.h | 28 + include/uapi/linux/media.h | 8 + include/uapi/linux/videodev2.h | 6 +- 18 files changed, 1408 insertions(+), 65 deletions(-) create mode 100644 drivers/media/media-request.c create mode 100644 include/media/media-request.h -- 2.7.4
