Re: [V4l2-library] Messed up syscall return value

[Gregor Jasny <jasny@vidsoft.de>]

On Tue, Jul 29, 2008 at 12:00:34PM +0200, Hans de Goede wrote:
> Indeed, so iow I'm happy to conclude that thie is not a libv4l bug :)

Will you add a work around like the above in libv4l?

Thanks,
Gregor

Index: libv4l2/libv4l2.c
===================================================================
RCS file: /var/cvs/vidsoft/extern/libv4l/libv4l2/libv4l2.c,v
retrieving revision 1.5
diff -u -r1.5 libv4l2.c
--- libv4l2/libv4l2.c	14 Jul 2008 14:00:28 -0000	1.5
+++ libv4l2/libv4l2.c	29 Jul 2008 11:51:20 -0000
@@ -97,7 +97,7 @@
   req.count = devices[index].nreadbuffers;
   req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
   req.memory = V4L2_MEMORY_MMAP;
-  if ((result = syscall(SYS_ioctl, devices[index].fd, VIDIOC_REQBUFS, &req))){
+  if ((result = syscall(SYS_ioctl, devices[index].fd, VIDIOC_REQBUFS, &req)) < 0){
     int saved_err = errno;
     V4L2_LOG_ERR("requesting buffers: %s\n", strerror(errno));
     errno = saved_err;
@@ -121,7 +121,7 @@
   req.count = 0;
   req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
   req.memory = V4L2_MEMORY_MMAP;
-  if ((result = syscall(SYS_ioctl, devices[index].fd, VIDIOC_REQBUFS, &req))) {
+  if ((result = syscall(SYS_ioctl, devices[index].fd, VIDIOC_REQBUFS, &req)) < 0) {
     int saved_err = errno;
     V4L2_LOG_ERR("unrequesting buffers: %s\n", strerror(errno));
     errno = saved_err;
@@ -723,8 +723,9 @@
 	v4l2_unmap_buffers(index);
 
 	result = syscall(SYS_ioctl, devices[index].fd, VIDIOC_REQBUFS, req);
-	if (result)
+	if (result < 0)
 	  break;
+	result = 0; // some drivers return the number of buffers on success
 
 	/* If we got more frames then we can handle lie to the app */
 	if (req->count > V4L2_MAX_NO_FRAMES)

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