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{
    "id": 3939,
    "url": "https://patchwork.libcamera.org/api/patches/3939/?format=api",
    "web_url": "https://patchwork.libcamera.org/patch/3939/",
    "project": {
        "id": 1,
        "url": "https://patchwork.libcamera.org/api/projects/1/?format=api",
        "name": "libcamera",
        "link_name": "libcamera",
        "list_id": "libcamera_core",
        "list_email": "libcamera-devel@lists.libcamera.org",
        "web_url": "",
        "scm_url": "",
        "webscm_url": ""
    },
    "msgid": "<20200605090106.15424-5-paul.elder@ideasonboard.com>",
    "date": "2020-06-05T09:01:03",
    "name": "[libcamera-devel,v2,4/7] v4l2: v4l2_camera_proxy: Acquire only one buffer semaphore on VIDIOC_DQBUF",
    "commit_ref": null,
    "pull_url": null,
    "state": "accepted",
    "archived": false,
    "hash": "78b0f8725dc4d15d7e2b13465d287af842022f4d",
    "submitter": {
        "id": 17,
        "url": "https://patchwork.libcamera.org/api/people/17/?format=api",
        "name": "Paul Elder",
        "email": "paul.elder@ideasonboard.com"
    },
    "delegate": null,
    "mbox": "https://patchwork.libcamera.org/patch/3939/mbox/",
    "series": [
        {
            "id": 956,
            "url": "https://patchwork.libcamera.org/api/series/956/?format=api",
            "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=956",
            "date": "2020-06-05T09:00:59",
            "name": "Support qv4l2 with v4l2-compat",
            "version": 2,
            "mbox": "https://patchwork.libcamera.org/series/956/mbox/"
        }
    ],
    "comments": "https://patchwork.libcamera.org/api/patches/3939/comments/",
    "check": "pending",
    "checks": "https://patchwork.libcamera.org/api/patches/3939/checks/",
    "tags": {},
    "headers": {
        "Return-Path": "<paul.elder@ideasonboard.com>",
        "Received": [
            "from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 8591E61027\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tFri,  5 Jun 2020 11:01:22 +0200 (CEST)",
            "from emerald.amanokami.net (fs76eef344.knge213.ap.nuro.jp\n\t[118.238.243.68])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 57D6B27C;\n\tFri,  5 Jun 2020 11:01:21 +0200 (CEST)"
        ],
        "Authentication-Results": "lancelot.ideasonboard.com; dkim=pass (1024-bit key; \n\tunprotected) header.d=ideasonboard.com\n\theader.i=@ideasonboard.com\n\theader.b=\"XZ7280gF\"; dkim-atps=neutral",
        "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1591347682;\n\tbh=QB20CXQv4BOODnqeSakNDMIm1j3itxDVfiqH16KTQ/Q=;\n\th=From:To:Cc:Subject:Date:In-Reply-To:References:From;\n\tb=XZ7280gFjPQF05Rh1AnVS28JHClLRD5mYIAFZB53Y6xfhLkH9mqjG12GfoId/ttCZ\n\tmwpxgN4AnW0FSbUhByLZt3BrHD+OrZ1QsjvsAfD1HNdR/q1jrYoZsPcax5AvLkZRMz\n\tY0iu31m51U8zVExOxLMLsxuZI0tZ7rvifD5aS/AY=",
        "From": "Paul Elder <paul.elder@ideasonboard.com>",
        "To": "libcamera-devel@lists.libcamera.org",
        "Date": "Fri,  5 Jun 2020 18:01:03 +0900",
        "Message-Id": "<20200605090106.15424-5-paul.elder@ideasonboard.com>",
        "X-Mailer": "git-send-email 2.20.1",
        "In-Reply-To": "<20200605090106.15424-1-paul.elder@ideasonboard.com>",
        "References": "<20200605090106.15424-1-paul.elder@ideasonboard.com>",
        "MIME-Version": "1.0",
        "Content-Transfer-Encoding": "8bit",
        "Subject": "[libcamera-devel] [PATCH v2 4/7] v4l2: v4l2_camera_proxy: Acquire\n\tonly one buffer semaphore on VIDIOC_DQBUF",
        "X-BeenThere": "libcamera-devel@lists.libcamera.org",
        "X-Mailman-Version": "2.1.29",
        "Precedence": "list",
        "List-Id": "<libcamera-devel.lists.libcamera.org>",
        "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>",
        "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>",
        "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>",
        "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>",
        "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>",
        "X-List-Received-Date": "Fri, 05 Jun 2020 09:01:22 -0000"
    },
    "content": "We use a semaphore to atomically keep track of how many buffers are\navailable for dequeueing. The check for how to acquire the semaphore was\nincorrect, leading to a double acquire upon a successful nonblocking\nacquire. Fix this.\n\nSigned-off-by: Paul Elder <paul.elder@ideasonboard.com>\n\n---\nChanges in v2: restructured the if block so it's easier to read\n---\n src/v4l2/v4l2_camera_proxy.cpp | 6 +++---\n 1 file changed, 3 insertions(+), 3 deletions(-)",
    "diff": "diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp\nindex ec6d265d..a0c6deea 100644\n--- a/src/v4l2/v4l2_camera_proxy.cpp\n+++ b/src/v4l2/v4l2_camera_proxy.cpp\n@@ -426,10 +426,10 @@ int V4L2CameraProxy::vidioc_dqbuf(struct v4l2_buffer *arg)\n \t    !validateMemoryType(arg->memory))\n \t\treturn -EINVAL;\n \n-\tif (nonBlocking_ && !vcam_->bufferSema_.tryAcquire())\n-\t\treturn -EAGAIN;\n-\telse\n+\tif (!nonBlocking_)\n \t\tvcam_->bufferSema_.acquire();\n+\telse if (!vcam_->bufferSema_.tryAcquire())\n+\t\treturn -EAGAIN;\n \n \tupdateBuffers();\n \n",
    "prefixes": [
        "libcamera-devel",
        "v2",
        "4/7"
    ]
}