)]}'
{
  "log": [
    {
      "commit": "b25b086d23eb852bf3cfdeb60409b4967ebb3c0c",
      "tree": "b7c40775fe47606e319f1d2dab3842ad3460c316",
      "parents": [
        "12c4727e1d5370270a7df781d2ba0a76e05c1137"
      ],
      "author": {
        "name": "Dave Airlie",
        "email": "airlied@redhat.com",
        "time": "Tue May 22 13:34:38 2012 +0100"
      },
      "committer": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Fri May 25 12:51:11 2012 +0530"
      },
      "message": "dma-buf: add initial vmap documentation\n\nSigned-off-by: Dave Airlie \u003cairlied@redhat.com\u003e\nSigned-off-by: Sumit Semwal \u003csumit.semwal@linaro.org\u003e\n"
    },
    {
      "commit": "4c78513e457f72d5554a0f6e2eabfad7b98e4f19",
      "tree": "2cdb5c552580f159ff66632aef781e8739c85c42",
      "parents": [
        "76e10d158efb6d4516018846f60c2ab5501900bc"
      ],
      "author": {
        "name": "Daniel Vetter",
        "email": "daniel.vetter@ffwll.ch",
        "time": "Tue Apr 24 14:38:52 2012 +0530"
      },
      "committer": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Fri May 25 12:35:24 2012 +0530"
      },
      "message": "dma-buf: mmap support\n\nCompared to Rob Clark\u0027s RFC I\u0027ve ditched the prepare/finish hooks\nand corresponding ioctls on the dma_buf file. The major reason for\nthat is that many people seem to be under the impression that this is\nalso for synchronization with outstanding asynchronous processsing.\nI\u0027m pretty massively opposed to this because:\n\n- It boils down reinventing a new rather general-purpose userspace\n  synchronization interface. If we look at things like futexes, this\n  is hard to get right.\n- Furthermore a lot of kernel code has to interact with this\n  synchronization primitive. This smells a look like the dri1 hw_lock,\n  a horror show I prefer not to reinvent.\n- Even more fun is that multiple different subsystems would interact\n  here, so we have plenty of opportunities to create funny deadlock\n  scenarios.\n\nI think synchronization is a wholesale different problem from data\nsharing and should be tackled as an orthogonal problem.\n\nNow we could demand that prepare/finish may only ensure cache\ncoherency (as Rob intended), but that runs up into the next problem:\nWe not only need mmap support to facilitate sw-only processing nodes\nin a pipeline (without jumping through hoops by importing the dma_buf\ninto some sw-access only importer), which allows for a nicer\nION-\u003edma-buf upgrade path for existing Android userspace. We also need\nmmap support for existing importing subsystems to support existing\nuserspace libraries. And a loot of these subsystems are expected to\nexport coherent userspace mappings.\n\nSo prepare/finish can only ever be optional and the exporter /needs/\nto support coherent mappings. Given that mmap access is always\nsomewhat fallback-y in nature I\u0027ve decided to drop this optimization,\ninstead of just making it optional. If we demonstrate a clear need for\nthis, supported by benchmark results, we can always add it in again\nlater as an optional extension.\n\nOther differences compared to Rob\u0027s RFC is the above mentioned support\nfor mapping a dma-buf through facilities provided by the importer.\nWhich results in mmap support no longer being optional.\n\nNote that this dma-buf mmap patch does _not_ support every possible\ninsanity an existing subsystem could pull of with mmap: Because it\ndoes not allow to intercept pagefaults and shoot down ptes importing\nsubsystems can\u0027t add some magic of their own at these points (e.g. to\nautomatically synchronize with outstanding rendering or set up some\nspecial resources). I\u0027ve done a cursory read through a few mmap\nimplementions of various subsytems and I\u0027m hopeful that we can avoid\nthis (and the complexity it\u0027d bring with it).\n\nAdditonally I\u0027ve extended the documentation a bit to explain the hows\nand whys of this mmap extension.\n\nIn case we ever want to add support for explicitly cache maneged\nuserspace mmap with a prepare/finish ioctl pair, we could specify that\nuserspace needs to mmap a different part of the dma_buf, e.g. the\nrange starting at dma_buf-\u003esize up to dma_buf-\u003esize*2. This works\nbecause the size of a dma_buf is invariant over it\u0027s lifetime. The\nexporter would obviously need to fall back to coherent mappings for\nboth ranges if a legacy clients maps the coherent range and the\narchitecture cannot suppor conflicting caching policies. Also, this\nwould obviously be optional and userspace needs to be able to fall\nback to coherent mappings.\n\nv2:\n- Spelling fixes from Rob Clark.\n- Compile fix for !DMA_BUF from Rob Clark.\n- Extend commit message to explain how explicitly cache managed mmap\n  support could be added later.\n- Extend the documentation with implementations notes for exporters\n  that need to manually fake coherency.\n\nv3:\n- dma_buf pointer initialization goof-up noticed by Rebecca Schultz\n  Zavin.\n\nCc: Rob Clark \u003crob.clark@linaro.org\u003e\nCc: Rebecca Schultz Zavin \u003crebecca@android.com\u003e\nAcked-by: Rob Clark \u003crob.clark@linaro.org\u003e\nSigned-Off-by: Daniel Vetter \u003cdaniel.vetter@ffwll.ch\u003e\nSigned-off-by: Sumit Semwal \u003csumit.semwal@linaro.org\u003e\n"
    },
    {
      "commit": "fbb231e1a98cb0360b681b6a6195a619e98d7077",
      "tree": "c7a3bd8975fc2d6a7e2ab25df02402a489b350ac",
      "parents": [
        "b0b40f24848440aa65418532fe97d8d46acceb3d"
      ],
      "author": {
        "name": "Rob Clark",
        "email": "rob@ti.com",
        "time": "Mon Mar 19 16:42:49 2012 -0500"
      },
      "committer": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Mon Mar 26 11:33:22 2012 +0530"
      },
      "message": "dma-buf: document fd flags and O_CLOEXEC requirement\n\nOtherwise subsystems will get this wrong and end up with a second\nexport ioctl with the flag and O_CLOEXEC support added.\n\nSigned-off-by: Rob Clark \u003crob@ti.com\u003e\nReviewed-by: Daniel Vetter \u003cdaniel.vetter@ffwll.ch\u003e\nSigned-off-by: Sumit Semwal \u003csumit.semwal@linaro.org\u003e\n"
    },
    {
      "commit": "b0b40f24848440aa65418532fe97d8d46acceb3d",
      "tree": "905a24a4164741ebae7ed41a85c63474c1bdedd6",
      "parents": [
        "fc13020e086bfedf2afb95c91c026d5af1f80107"
      ],
      "author": {
        "name": "Daniel Vetter",
        "email": "daniel.vetter@ffwll.ch",
        "time": "Mon Mar 19 00:34:27 2012 +0100"
      },
      "committer": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Mon Mar 26 11:33:13 2012 +0530"
      },
      "message": "dma_buf: Add documentation for the new cpu access support\n\nv2: Fix spelling issues noticed by Rob Clark.\n\nSigned-off-by: Daniel Vetter \u003cdaniel.vetter@ffwll.ch\u003e\nSigned-off-by: Rob Clark \u003crob@ti.com\u003e\nSigned-off-by: Sumit Semwal \u003csumit.semwal@linaro.org\u003e\n"
    },
    {
      "commit": "081794564e3000e602de290d1121792c33b475a4",
      "tree": "60a29b4a679036bec42ec8a6ff3b5e611c655348",
      "parents": [
        "d099230cc355c485e556121c034b1fca5a5fd18b"
      ],
      "author": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Fri Jan 13 15:15:05 2012 +0530"
      },
      "committer": {
        "name": "Dave Airlie",
        "email": "airlied@redhat.com",
        "time": "Fri Jan 13 10:27:33 2012 +0000"
      },
      "message": "dma-buf: Documentation update for Kconfig select\n\nAs per Linus\u0027 comment, dma-buf Kconfig entry shouldn\u0027t have an option\ntext, but should be selected by the subsystems that use it.\n\nAdd this information in the documentation as well.\n\nSigned-off-by: Sumit Semwal \u003csumit.semwal@ti.com\u003e\nSigned-off-by: Dave Airlie \u003cairlied@redhat.com\u003e\n"
    },
    {
      "commit": "a7df4719a3ca1c839bf703c5eca3a9c430466696",
      "tree": "1026f377b2f9051f3a382cdcff901a2ab7434a71",
      "parents": [
        "d15bd7ee445d0702ad801fdaece348fdb79e6581"
      ],
      "author": {
        "name": "Sumit Semwal",
        "email": "sumit.semwal@ti.com",
        "time": "Mon Dec 26 14:53:16 2011 +0530"
      },
      "committer": {
        "name": "Dave Airlie",
        "email": "airlied@redhat.com",
        "time": "Fri Jan 06 10:20:24 2012 +0000"
      },
      "message": "dma-buf: Documentation for buffer sharing framework\n\nAdd documentation for dma buffer sharing framework, explaining the\nvarious operations, members and API of the dma buffer sharing\nframework.\n\nSigned-off-by: Sumit Semwal \u003csumit.semwal@linaro.org\u003e\nSigned-off-by: Sumit Semwal \u003csumit.semwal@ti.com\u003e\nReviewed-by: Daniel Vetter \u003cdaniel.vetter@ffwll.ch\u003e\nSigned-off-by: Dave Airlie \u003cairlied@redhat.com\u003e\n"
    }
  ]
}