From 96eb602808db2c09e4fea2d36a5360f9fbf71c42 Mon Sep 17 00:00:00 2001
From: josh <josh@bd8a9e45-a331-0410-811e-c64571078777>
Date: Fri, 7 Aug 2009 23:06:58 +0000
Subject: [PATCH] requesting and memory-mapping a buffer

git-svn-id: svn://anubis/misc/WebcamTracker@121 bd8a9e45-a331-0410-811e-c64571078777
---
 WebcamTracker.cc | 94 +++++++++++++++++++++++++++++++++++++-----------
 WebcamTracker.h  |  2 ++
 2 files changed, 76 insertions(+), 20 deletions(-)

diff --git a/WebcamTracker.cc b/WebcamTracker.cc
index 3ba7ada..3bf1b7b 100644
--- a/WebcamTracker.cc
+++ b/WebcamTracker.cc
@@ -5,6 +5,9 @@
 #include <stdlib.h>                 /* exit() */
 #include <sys/ioctl.h>              /* ioctl() */
 #include <libv4lconvert.h>
+#include <unistd.h>
+#include <sys/mman.h>               /* mmap() */
+#include <errno.h>
 #include <iostream>
 #include "WebcamTracker.h"
 using namespace std;
@@ -23,26 +26,61 @@ WebcamTracker::WebcamTracker(const char * device)
         m_open = true;
 
         struct v4l2_capability cap;
-        ioctl(m_fd, VIDIOC_QUERYCAP, &cap);
-#define check_cap(x) do { \
-    if (cap.capabilities & (x)) \
-        cout << " cap: " << #x << endl; \
-    } while (0)
-        check_cap(V4L2_CAP_VIDEO_CAPTURE);
-        check_cap(V4L2_CAP_VIDEO_OUTPUT);
-        check_cap(V4L2_CAP_VIDEO_OVERLAY);
-        check_cap(V4L2_CAP_VBI_CAPTURE);
-        check_cap(V4L2_CAP_VBI_OUTPUT);
-        check_cap(V4L2_CAP_SLICED_VBI_CAPTURE);
-        check_cap(V4L2_CAP_SLICED_VBI_OUTPUT);
-        check_cap(V4L2_CAP_RDS_CAPTURE);
-        check_cap(V4L2_CAP_VIDEO_OUTPUT_OVERLAY);
-        check_cap(V4L2_CAP_TUNER);
-        check_cap(V4L2_CAP_AUDIO);
-        check_cap(V4L2_CAP_RADIO);
-        check_cap(V4L2_CAP_READWRITE);
-        check_cap(V4L2_CAP_ASYNCIO);
-        check_cap(V4L2_CAP_STREAMING);
+        int ret = ioctl(m_fd, VIDIOC_QUERYCAP, &cap);
+        if (ret != 0)
+        {
+            cerr << "VIDIOC_QUERYCAP ioctl failed: " << ret << endl;
+        }
+        if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
+        {
+            cerr << "Warning: V4L2_CAP_VIDEO_CAPTURE not supported!" << endl;
+        }
+
+        v4l2_requestbuffers reqbuf;
+        reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        reqbuf.count = 1;
+        reqbuf.memory = V4L2_MEMORY_MMAP;
+        ret = ioctl(m_fd, VIDIOC_REQBUFS, &reqbuf);
+        if (ret != 0)
+        {
+            cerr << "VIDIOC_REQBUFS ioctl failed: returned " << ret
+                 << ", errno " << errno;
+            if (errno == EBUSY)
+                cerr << " (EBUSY)";
+            if (errno == EINVAL)
+                cerr << " (EINVAL)";
+            cerr << endl;
+        }
+
+        struct v4l2_buffer buf;
+        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        buf.index = 0;
+        ret = ioctl(m_fd, VIDIOC_QUERYBUF, &buf);
+        if (ret != 0)
+        {
+            cerr << "VIDIOC_QUERYBUF ioctl failed: returned " << ret
+                 << ", errno: " << errno;
+            if (errno == EINVAL)
+                cerr << " (EINVAL)";
+            cerr << endl;
+        }
+
+        m_vidbuflen = buf.length;
+        m_vidbuf = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED,
+                        m_fd, buf.m.offset);
+        if (m_vidbuf == MAP_FAILED)
+        {
+            cerr << "mmap() failed: errno " << errno;
+            if (errno == EBADF)
+                cerr << " (EBADF)";
+            if (errno == EACCES)
+                cerr << " (EACCES)";
+            if (errno == EINVAL)
+                cerr << " (EINVAL)";
+            if (errno == ENOMEM)
+                cerr << " (ENOMEM)";
+            cerr << endl;
+        }
     }
     else
     {
@@ -54,6 +92,22 @@ WebcamTracker::~WebcamTracker()
 {
     if (m_open)
     {
+        munmap(m_vidbuf, m_vidbuflen);
+
+        v4l2_requestbuffers reqbuf;
+        reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+        reqbuf.count = 0;
+        reqbuf.memory = V4L2_MEMORY_MMAP;
+        int ret = ioctl(m_fd, VIDIOC_REQBUFS, &reqbuf);
+        if (ret != 0)
+        {
+            cerr << "~WebcamTracker(): VIDIOC_REQBUFS ioctl failed: "
+                 << ret << endl;
+            if (errno == EBUSY)
+                cerr << "EBUSY" << endl;
+            if (errno == EINVAL)
+                cerr << "EINVAL" << endl;
+        }
         close(m_fd);
     }
 }
diff --git a/WebcamTracker.h b/WebcamTracker.h
index 3f04398..d7c5ad3 100644
--- a/WebcamTracker.h
+++ b/WebcamTracker.h
@@ -14,6 +14,8 @@ class WebcamTracker
         ~WebcamTracker();
 
     protected:
+        void *  m_vidbuf;
+        int     m_vidbuflen;
         bool    m_open;
         int     m_fd;
 };