Re: [PATCH 1/1 v3] libv4l: Add plugin support to libv4l

[Hans de Goede <hdegoede@redhat.com>]

Hi,

First of all my apologies for taking so long to get around to
reviewing this.

Over all it looks good, I've put some small remarks inline, if
you fix these I can merge this. I wonder though, given the recent
limbo around Nokia's change of focus, if there are any plans to
actually move forward with a plugin using this... ?

The reason I'm asking is that adding the plugin framework if nothing
is going to use it seems a bit senseless.

Regards,

Hans


On 02/14/2011 12:02 PM, Yordan Kamenov wrote:
> A libv4l2 plugin will sit in between libv4l2 itself and the actual
> /dev/video device node a fd refers to. It will be called each time
> libv4l2 wants to do an operation (read/write/ioctl) on the actual
> /dev/video node in question.
>
> Signed-off-by: Yordan Kamenov<ykamenov@mm-sol.com>
> ---
>   lib/include/libv4l2-plugin.h                   |   36 ++++++
>   lib/include/libv4lconvert.h                    |    5 +-
>   lib/libv4l2/Makefile                           |    4 +-
>   lib/libv4l2/libv4l2-priv.h                     |   10 ++
>   lib/libv4l2/libv4l2.c                          |   90 ++++++++++----
>   lib/libv4l2/v4l2-plugin.c                      |  160 ++++++++++++++++++++++++
>   lib/libv4l2/v4l2convert.c                      |    9 --
>   lib/libv4lconvert/control/libv4lcontrol-priv.h |    4 +
>   lib/libv4lconvert/control/libv4lcontrol.c      |   35 ++++--
>   lib/libv4lconvert/control/libv4lcontrol.h      |    5 +-
>   lib/libv4lconvert/libv4lconvert-priv.h         |    2 +
>   lib/libv4lconvert/libv4lconvert.c              |   34 ++++--
>   12 files changed, 333 insertions(+), 61 deletions(-)
>   create mode 100644 lib/include/libv4l2-plugin.h
>   create mode 100644 lib/libv4l2/v4l2-plugin.c
>
> diff --git a/lib/include/libv4l2-plugin.h b/lib/include/libv4l2-plugin.h
> new file mode 100644
> index 0000000..5cb666a
> --- /dev/null
> +++ b/lib/include/libv4l2-plugin.h
> @@ -0,0 +1,36 @@
> +/*
> +* Copyright (C) 2010 Nokia Corporation<multimedia@maemo.org>
> +
> +* This program is free software; you can redistribute it and/or modify
> +* it under the terms of the GNU Lesser General Public License as published by
> +* the Free Software Foundation; either version 2.1 of the License, or
> +* (at your option) any later version.
> +*
> +* This program is distributed in the hope that it will be useful,
> +* but WITHOUT ANY WARRANTY; without even the implied warranty of
> +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +* Lesser General Public License for more details.
> +*
> +* You should have received a copy of the GNU Lesser General Public License
> +* along with this program; if not, write to the Free Software
> +* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> +*/
> +
> +#ifndef __LIBV4L2_PLUGIN_H
> +#define __LIBV4L2_PLUGIN_H
> +
> +#include<sys/types.h>
> +
> +/* Structure libv4l2_dev_ops holds the calls from libv4ls to video nodes.
> +   They can be normal open/close/ioctl etc. or any of them may be replaced
> +   with a callback by a loaded plugin.
> +*/
> +
> +struct libv4l2_dev_ops {
> +    void * (*init)(int fd);
> +    int (*close)(void *dev_ops_priv);

Since you don't error check the close callback's return value in the
single place you call it, you might just as well make it void

> +    int (*ioctl)(void *dev_ops_priv, int fd, unsigned long int request, void *arg);
> +    ssize_t (*read)(void *dev_ops_priv, int fd, void *buffer, size_t n);
> +};
> +
> +#endif
> diff --git a/lib/include/libv4lconvert.h b/lib/include/libv4lconvert.h
> index 0264290..351142e 100644
> --- a/lib/include/libv4lconvert.h
> +++ b/lib/include/libv4lconvert.h
> @@ -38,6 +38,8 @@
>
>   #include<linux/videodev2.h>
>
> +#include "libv4l2-plugin.h"
> +
>   #ifdef __cplusplus
>   extern "C" {
>   #endif /* __cplusplus */
> @@ -50,7 +52,8 @@ extern "C" {
>
>   struct v4lconvert_data;
>
> -LIBV4L_PUBLIC struct v4lconvert_data *v4lconvert_create(int fd);
> +LIBV4L_PUBLIC struct v4lconvert_data *v4lconvert_create(int fd,
> +		void *dev_ops_priv, struct libv4l2_dev_ops *dev_ops);
>   LIBV4L_PUBLIC void v4lconvert_destroy(struct v4lconvert_data *data);
>
>   /* When doing flipping / rotating / video-processing, only supported
> diff --git a/lib/libv4l2/Makefile b/lib/libv4l2/Makefile
> index d78632f..eb1c019 100644
> --- a/lib/libv4l2/Makefile
> +++ b/lib/libv4l2/Makefile
> @@ -1,8 +1,8 @@
>   override CPPFLAGS += -I../include -fvisibility=hidden
>
> -LIBS_libv4l2  = -lpthread
> +LIBS_libv4l2  = -lpthread -ldl
>
> -V4L2_OBJS     = libv4l2.o log.o
> +V4L2_OBJS     = libv4l2.o v4l2-plugin.o log.o
>   V4L2CONVERT   = v4l2convert.so
>   V4L2CONVERT_O = v4l2convert.o libv4l2.so
>   TARGETS       = $(V4L2_LIB) libv4l2.pc
> diff --git a/lib/libv4l2/libv4l2-priv.h b/lib/libv4l2/libv4l2-priv.h
> index 46d6103..d06a508 100644
> --- a/lib/libv4l2/libv4l2-priv.h
> +++ b/lib/libv4l2/libv4l2-priv.h
> @@ -85,8 +85,18 @@ struct v4l2_dev_info {
>   	/* buffer when doing conversion and using read() for read() */
>   	int readbuf_size;
>   	unsigned char *readbuf;
> +	struct libv4l2_dev_ops *dev_ops;
> +	/* plugin info */
> +	void *plugin_library;
> +	void *dev_ops_priv;
>   };
>
> +void v4l2_plugin_init(int fd, void **plugin_lib_ret, void **plugin_priv_ret,
> +					struct libv4l2_dev_ops **dev_ops_ret);
> +void v4l2_plugin_cleanup(void *plugin_priv, void *plugin_lib,
> +					struct libv4l2_dev_ops *dev_ops);
> +
> +
>   /* From log.c */
>   void v4l2_log_ioctl(unsigned long int request, void *arg, int result);
>
> diff --git a/lib/libv4l2/libv4l2.c b/lib/libv4l2/libv4l2.c
> index ab85ea7..2b717a8 100644
> --- a/lib/libv4l2/libv4l2.c
> +++ b/lib/libv4l2/libv4l2.c
> @@ -67,6 +67,7 @@
>   #include<sys/stat.h>
>   #include "libv4l2.h"
>   #include "libv4l2-priv.h"
> +#include "libv4l2-plugin.h"
>
>   /* Note these flags are stored together with the flags passed to v4l2_fd_open()
>      in v4l2_dev_info's flags member, so care should be taken that the do not
> @@ -102,7 +103,8 @@ static int v4l2_request_read_buffers(int index)
>   		devices[index].nreadbuffers;
>   	req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>   	req.memory = V4L2_MEMORY_MMAP;
> -	result = SYS_IOCTL(devices[index].fd, VIDIOC_REQBUFS,&req);
> +	result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +			devices[index].fd, VIDIOC_REQBUFS,&req);
>   	if (result<  0) {
>   		int saved_err = errno;
>
> @@ -131,7 +133,8 @@ static void v4l2_unrequest_read_buffers(int index)
>   	req.count = 0;
>   	req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>   	req.memory = V4L2_MEMORY_MMAP;
> -	if (SYS_IOCTL(devices[index].fd, VIDIOC_REQBUFS,&req)<  0)
> +	if (devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +			devices[index].fd, VIDIOC_REQBUFS,&req)<  0)
>   		return;
>
>   	devices[index].no_frames = MIN(req.count, V4L2_MAX_NO_FRAMES);
> @@ -152,7 +155,8 @@ static int v4l2_map_buffers(int index)
>   		buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>   		buf.memory = V4L2_MEMORY_MMAP;
>   		buf.index = i;
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_QUERYBUF,&buf);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_QUERYBUF,&buf);
>   		if (result) {
>   			int saved_err = errno;
>
> @@ -202,7 +206,8 @@ static int v4l2_streamon(int index)
>   	enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>
>   	if (!(devices[index].flags&  V4L2_STREAMON)) {
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_STREAMON,&type);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_STREAMON,&type);
>   		if (result) {
>   			int saved_err = errno;
>
> @@ -223,7 +228,8 @@ static int v4l2_streamoff(int index)
>   	enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>
>   	if (devices[index].flags&  V4L2_STREAMON) {
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_STREAMOFF,&type);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_STREAMOFF,&type);
>   		if (result) {
>   			int saved_err = errno;
>
> @@ -252,7 +258,8 @@ static int v4l2_queue_read_buffer(int index, int buffer_index)
>   	buf.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>   	buf.memory = V4L2_MEMORY_MMAP;
>   	buf.index  = buffer_index;
> -	result = SYS_IOCTL(devices[index].fd, VIDIOC_QBUF,&buf);
> +	result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +			devices[index].fd, VIDIOC_QBUF,&buf);
>   	if (result) {
>   		int saved_err = errno;
>
> @@ -277,7 +284,8 @@ static int v4l2_dequeue_and_convert(int index, struct v4l2_buffer *buf,
>   		return result;
>
>   	do {
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_DQBUF, buf);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_DQBUF, buf);
>   		if (result) {
>   			if (errno != EAGAIN) {
>   				int saved_err = errno;
> @@ -356,7 +364,8 @@ static int v4l2_read_and_convert(int index, unsigned char *dest, int dest_size)
>   	}
>
>   	do {
> -		result = SYS_READ(devices[index].fd, devices[index].readbuf, buf_size);
> +		result = devices[index].dev_ops->read(devices[index].dev_ops_priv,
> +				devices[index].fd, devices[index].readbuf, buf_size);
>   		if (result<= 0) {
>   			if (result&&  errno != EAGAIN) {
>   				int saved_err = errno;
> @@ -496,7 +505,8 @@ static int v4l2_buffers_mapped(int index)
>   			buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>   			buf.memory = V4L2_MEMORY_MMAP;
>   			buf.index = i;
> -			if (SYS_IOCTL(devices[index].fd, VIDIOC_QUERYBUF,&buf)) {
> +			if (devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +					devices[index].fd, VIDIOC_QUERYBUF,&buf)) {
>   				int saved_err = errno;
>
>   				V4L2_LOG_ERR("querying buffer %u: %s\n", i, strerror(errno));
> @@ -561,6 +571,11 @@ int v4l2_fd_open(int fd, int v4l2_flags)
>   	struct v4l2_capability cap;
>   	struct v4l2_format fmt;
>   	struct v4lconvert_data *convert;
> +	struct libv4l2_dev_ops *dev_ops;
> +	void *plugin_library;
> +	void *plugin_data;
> +
> +	v4l2_plugin_init(fd,&plugin_library,&plugin_data,&dev_ops);
>
>   	/* If no log file was set by the app, see if one was specified through the
>   	   environment */
> @@ -571,9 +586,10 @@ int v4l2_fd_open(int fd, int v4l2_flags)
>   	}
>
>   	/* check that this is an v4l2 device */
> -	if (SYS_IOCTL(fd, VIDIOC_QUERYCAP,&cap)) {
> +	if (dev_ops->ioctl(plugin_data, fd, VIDIOC_QUERYCAP,&cap)) {
>   		int saved_err = errno;
>
> +		v4l2_plugin_cleanup(plugin_data, plugin_library, dev_ops);
>   		V4L2_LOG_ERR("getting capabilities: %s\n", strerror(errno));
>   		errno = saved_err;
>   		return -1;
> @@ -581,29 +597,38 @@ int v4l2_fd_open(int fd, int v4l2_flags)
>
>   	/* we only add functionality for video capture devices */
>   	if (!(cap.capabilities&  V4L2_CAP_VIDEO_CAPTURE) ||
> -			!(cap.capabilities&  (V4L2_CAP_STREAMING | V4L2_CAP_READWRITE)))
> +			!(cap.capabilities&  (V4L2_CAP_STREAMING | V4L2_CAP_READWRITE))) {
> +		v4l2_plugin_cleanup(plugin_data, plugin_library, dev_ops);
>   		return fd;
> +	}
>
>   	/* Get current cam format */
>   	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> -	if (SYS_IOCTL(fd, VIDIOC_G_FMT,&fmt)) {
> +	if (dev_ops->ioctl(plugin_data, fd, VIDIOC_G_FMT,&fmt)) {
>   		int saved_err = errno;
>
> +		v4l2_plugin_cleanup(plugin_data, plugin_library, dev_ops);
>   		V4L2_LOG_ERR("getting pixformat: %s\n", strerror(errno));
>   		errno = saved_err;
>   		return -1;
>   	}
>
>   	/* init libv4lconvert */
> -	convert = v4lconvert_create(fd);
> -	if (!convert)
> +	convert = v4lconvert_create(fd, plugin_data, dev_ops);
> +	if (!convert) {
> +		v4l2_plugin_cleanup(plugin_data, plugin_library, dev_ops);
>   		return -1;
> +	}
>
>   	/* So we have a v4l2 capture device, register it in our devices array */
>   	pthread_mutex_lock(&v4l2_open_mutex);
>   	for (index = 0; index<  V4L2_MAX_DEVICES; index++)
>   		if (devices[index].fd == -1) {
>   			devices[index].fd = fd;
> +
> +			devices[index].plugin_library = plugin_library;
> +			devices[index].dev_ops_priv = plugin_data;
> +			devices[index].dev_ops = dev_ops;
>   			break;
>   		}
>   	pthread_mutex_unlock(&v4l2_open_mutex);
> @@ -611,6 +636,7 @@ int v4l2_fd_open(int fd, int v4l2_flags)
>   	if (index == V4L2_MAX_DEVICES) {
>   		V4L2_LOG_ERR("attempting to open more then %d video devices\n",
>   				V4L2_MAX_DEVICES);
> +		v4l2_plugin_cleanup(plugin_data, plugin_library, dev_ops);
>   		errno = EBUSY;
>   		return -1;
>   	}
> @@ -690,6 +716,9 @@ int v4l2_close(int fd)
>   	if (index == -1)
>   		return SYS_CLOSE(fd);
>
> +	v4l2_plugin_cleanup(devices[index].dev_ops_priv,
> +			devices[index].plugin_library, devices[index].dev_ops);
> +

This should be moved lower, to were the actual fd gets closed, if the fd
was opened multiple times (through dup) the plugin stuff should not
be cleaned up yet...

>   	/* Abuse stream_lock to stop 2 closes from racing and trying to free the
>   	   resources twice */
>   	pthread_mutex_lock(&devices[index].stream_lock);
> @@ -808,6 +837,7 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   	va_list ap;
>   	int result, index, saved_err;
>   	int is_capture_request = 0, stream_needs_locking = 0;
> +	void *plugin_data;
>
>   	va_start(ap, request);
>   	arg = va_arg(ap, void *);
> @@ -817,6 +847,7 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   	if (index == -1)
>   		return SYS_IOCTL(fd, request, arg);
>
> +	plugin_data = devices[index].dev_ops_priv;
>   	/* Appearantly the kernel and / or glibc ignore the 32 most significant bits
>   	   when long = 64 bits, and some applications pass an int holding the req to
>   	   ioctl, causing it to get sign extended, depending upon this behavior */

You don't seem to use plugin_data consistently in the function, see below.

> @@ -879,7 +910,7 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   	}
>
>   	if (!is_capture_request) {
> -		result = SYS_IOCTL(fd, request, arg);
> +		result = devices[index].dev_ops->ioctl(plugin_data, fd, request, arg);
>   		saved_err = errno;
>   		v4l2_log_ioctl(request, arg, result);
>   		errno = saved_err;

This is the 1 of places where you actually use plugin_data, either use it everywhere,
or drop it.

> @@ -927,7 +958,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   	case VIDIOC_QUERYCAP: {
>   		struct v4l2_capability *cap = arg;
>
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_QUERYCAP, cap);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_QUERYCAP, cap);
>   		if (result == 0)
>   			/* We always support read() as we fake it using mmap mode */
>   			cap->capabilities |= V4L2_CAP_READWRITE;
> @@ -977,8 +1009,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   		}
>
>   		if (devices[index].flags&  V4L2_DISABLE_CONVERSION) {
> -			result = SYS_IOCTL(devices[index].fd, VIDIOC_TRY_FMT,
> -					dest_fmt);
> +			result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +					devices[index].fd, VIDIOC_TRY_FMT, dest_fmt);
>   			src_fmt = *dest_fmt;
>   		} else {
>   			result = v4lconvert_try_format(devices[index].convert, dest_fmt,
> @@ -1018,7 +1050,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   			break;
>
>   		req_pix_fmt = src_fmt.fmt.pix;
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_S_FMT,&src_fmt);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_S_FMT,&src_fmt);
>   		if (result) {
>   			saved_err = errno;
>   			V4L2_LOG_ERR("setting pixformat: %s\n", strerror(errno));
> @@ -1067,7 +1100,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   		if (req->count>  V4L2_MAX_NO_FRAMES)
>   			req->count = V4L2_MAX_NO_FRAMES;
>
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_REQBUFS, req);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_REQBUFS, req);
>   		if (result<  0)
>   			break;
>   		result = 0; /* some drivers return the number of buffers on success */
> @@ -1088,7 +1122,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>
>   		/* Do a real query even when converting to let the driver fill in
>   		   things like buf->field */
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_QUERYBUF, buf);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_QUERYBUF, buf);
>   		if (result || !v4l2_needs_conversion(index))
>   			break;
>
> @@ -1115,7 +1150,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   				break;
>   		}
>
> -		result = SYS_IOCTL(devices[index].fd, VIDIOC_QBUF, arg);
> +		result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +				devices[index].fd, VIDIOC_QBUF, arg);
>   		break;
>
>   	case VIDIOC_DQBUF: {
> @@ -1128,7 +1164,8 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   		}
>
>   		if (!v4l2_needs_conversion(index)) {
> -			result = SYS_IOCTL(devices[index].fd, VIDIOC_DQBUF, buf);
> +			result = devices[index].dev_ops->ioctl(devices[index].dev_ops_priv,
> +					devices[index].fd, VIDIOC_DQBUF, buf);
>   			if (result) {
>   				int saved_err = errno;
>
> @@ -1187,7 +1224,7 @@ int v4l2_ioctl(int fd, unsigned long int request, ...)
>   		break;
>
>   	default:
> -		result = SYS_IOCTL(fd, request, arg);
> +		result = devices[index].dev_ops->ioctl(plugin_data, fd, request, arg);
>   		break;
>   	}
>

This is the only other place you use plugin_data.

> @@ -1206,18 +1243,21 @@ ssize_t v4l2_read(int fd, void *dest, size_t n)
>   {
>   	ssize_t result;
>   	int saved_errno;
> +	void *plugin_data;
>   	int index = v4l2_get_index(fd);
>
>   	if (index == -1)
>   		return SYS_READ(fd, dest, n);
>
> +	plugin_data = devices[index].dev_ops_priv;
> +
>   	pthread_mutex_lock(&devices[index].stream_lock);
>
>   	/* When not converting and the device supports read let the kernel handle
>   	   it */
>   	if ((devices[index].flags&  V4L2_SUPPORTS_READ)&&
>   			!v4l2_needs_conversion(index)) {
> -		result = SYS_READ(fd, dest, n);
> +		result = devices[index].dev_ops->read(plugin_data, fd, dest, n);
>   		goto leave;
>   	}
>

I so no need for the plugin_data variable here, just use
devices[index].dev_ops_priv directly when you call dev_ops->read.

> diff --git a/lib/libv4l2/v4l2-plugin.c b/lib/libv4l2/v4l2-plugin.c
> new file mode 100644
> index 0000000..89bffc5
> --- /dev/null
> +++ b/lib/libv4l2/v4l2-plugin.c
> @@ -0,0 +1,160 @@
> +/*
> +* Copyright (C) 2010 Nokia Corporation<multimedia@maemo.org>
> +
> +* This program is free software; you can redistribute it and/or modify
> +* it under the terms of the GNU Lesser General Public License as published by
> +* the Free Software Foundation; either version 2.1 of the License, or
> +* (at your option) any later version.
> +*
> +* This program is distributed in the hope that it will be useful,
> +* but WITHOUT ANY WARRANTY; without even the implied warranty of
> +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +* Lesser General Public License for more details.
> +*
> +* You should have received a copy of the GNU Lesser General Public License
> +* along with this program; if not, write to the Free Software
> +* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> +*/
> +
> +#include<stdarg.h>
> +#include<dlfcn.h>
> +#include<fcntl.h>
> +#include<glob.h>
> +#include<sys/stat.h>
> +#include<sys/mman.h>
> +#include "libv4l2.h"
> +#include "libv4l2-priv.h"
> +#include "libv4l2-plugin.h"
> +
> +/* libv4l plugin support:
> +   it is provided by functions v4l2_plugin_[open,close,etc].
> +
> +   When open() is called libv4l dlopens files in /usr/lib[64]/libv4l/plugins
> +   1 at a time and call open callback passing through the applications
> +   parameters unmodified.
> +
> +   If a plugin is relevant for the specified device node, it can indicate so
> +   by returning a value other then -1 (the actual file descriptor).
> +   As soon as a plugin returns another value then -1 plugin loading stops and
> +   information about it (fd and corresponding library handle) is stored. For
> +   each function v4l2_[ioctl,read,close,etc] is called corresponding
> +   v4l2_plugin_* function which looks if there is loaded plugin for that file
> +   and call it's callbacks.
> +
> +   v4l2_plugin_* function indicates by it's first argument if plugin was used,
> +   and if it was not then v4l2_* functions proceed with their usual behavior.
> +*/
> +
> +#define PLUGINS_PATTERN "/usr/lib/libv4l/plugins/*.so"
> +
> +static void * dev_init(int fd)
> +{
> +	return NULL;
> +}
> +
> +static int dev_close(void *dev_ops_priv)
> +{
> +	return -1;
> +}
> +

-1 is an error? Why would the default plugin always return error on close?
Anyways as said before just make it void.

> +static int dev_ioctl(void *dev_ops_priv, int fd, unsigned long cmd, void *arg)
> +{
> +	return syscall(SYS_ioctl, (int)(fd), (unsigned long)(cmd),
> +			(void *)(arg));
> +}
> +
> +static ssize_t dev_read(void *dev_ops_priv, int fd, void *buf, size_t len)
> +{
> +	return syscall(SYS_read, (int)(fd), (void *)(buf), (size_t)(len));
> +}

Please use the SYS_IOCTL and SYS_READ macro's here for compat with freebsd.

> +
> +
> +struct libv4l2_dev_ops default_operations = {
> +	.init =&dev_init,
> +	.close =&dev_close,
> +	.ioctl =&dev_ioctl,
> +	.read =&dev_read
> +};
> +
> +void v4l2_plugin_init(int fd, void **plugin_lib_ret, void **plugin_priv_ret,
> +					struct libv4l2_dev_ops **dev_ops_ret)
> +{
> +	char *error;
> +	int glob_ret, plugin_num;
> +	void *plugin_library = NULL;
> +	struct libv4l2_dev_ops *libv4l2_plugin = NULL;
> +	glob_t globbuf;
> +
> +	*dev_ops_ret =&default_operations;
> +
> +	glob_ret = glob(PLUGINS_PATTERN, 0, NULL,&globbuf);
> +
> +	if (glob_ret == GLOB_NOSPACE) {
> +		*plugin_lib_ret = NULL;
> +		*plugin_priv_ret = NULL;
> +		return;
> +	}
> +
> +	if (glob_ret == GLOB_ABORTED || glob_ret == GLOB_NOMATCH) {
> +		*plugin_lib_ret = NULL;
> +		*plugin_priv_ret = NULL;
> +		goto leave;
> +	}
> +
> +	for (plugin_num = 0; plugin_num<  globbuf.gl_pathc; plugin_num++) {
> +
> +		V4L2_LOG("PLUGIN: dlopen(%s);\n", globbuf.gl_pathv[plugin_num]);
> +
> +		plugin_library = dlopen(globbuf.gl_pathv[plugin_num],
> +							RTLD_LAZY);
> +
> +		if (!plugin_library)
> +			continue;
> +
> +		dlerror();    /* Clear any existing error */
> +		libv4l2_plugin = (struct libv4l2_dev_ops *)
> +					dlsym(plugin_library, "libv4l2_plugin");
> +
> +		error = dlerror();
> +		if (error != NULL)  {
> +			V4L2_LOG_ERR("PLUGIN: dlsym failed: %s\n", error);
> +			dlclose(plugin_library);
> +
> +			continue;
> +		}
> +
> +		*plugin_priv_ret = NULL;
> +		if (libv4l2_plugin->init)
> +			*plugin_priv_ret = libv4l2_plugin->init(fd);
> +
> +		if (!*plugin_priv_ret) {
> +			V4L2_LOG("PLUGIN: plugin open() returned NULL\n");
> +			dlclose(plugin_library);
> +			*plugin_lib_ret = NULL;
> +			continue;
> +		}
> +
> +		(*dev_ops_ret)->init = libv4l2_plugin->init;
> +		if (libv4l2_plugin->close != NULL)
> +			(*dev_ops_ret)->close = libv4l2_plugin->close;
> +		if (libv4l2_plugin->ioctl != NULL)
> +			(*dev_ops_ret)->ioctl = libv4l2_plugin->ioctl;
> +		if (libv4l2_plugin->read != NULL)
> +			(*dev_ops_ret)->read = libv4l2_plugin->read;
> +
> +		break;
> +
> +	}
> +
> +leave:
> +	globfree(&globbuf);
> +}
> +
> +void v4l2_plugin_cleanup(void *plugin_priv, void *plugin_lib,
> +					struct libv4l2_dev_ops *dev_ops)
> +{
> +	if (plugin_priv) {
> +		dev_ops->close(plugin_priv);
> +		dlclose(plugin_lib);
> +	}
> +}
> diff --git a/lib/libv4l2/v4l2convert.c b/lib/libv4l2/v4l2convert.c
> index e251085..03f34ad 100644
> --- a/lib/libv4l2/v4l2convert.c
> +++ b/lib/libv4l2/v4l2convert.c
> @@ -46,7 +46,6 @@
>   LIBV4L_PUBLIC int open(const char *file, int oflag, ...)
>   {
>   	int fd;
> -	struct v4l2_capability cap;
>   	int v4l_device = 0;
>
>   	/* check if we're opening a video4linux2 device */
> @@ -76,14 +75,6 @@ LIBV4L_PUBLIC int open(const char *file, int oflag, ...)
>   	if (fd == -1 || !v4l_device)
>   		return fd;
>
> -	/* check that this is an v4l2 device, libv4l2 only supports v4l2 devices */
> -	if (SYS_IOCTL(fd, VIDIOC_QUERYCAP,&cap))
> -		return fd;
> -
> -	/* libv4l2 only adds functionality to capture capable devices */
> -	if (!(cap.capabilities&  V4L2_CAP_VIDEO_CAPTURE))
> -		return fd;
> -
>   	/* Try to Register with libv4l2 (in case of failure pass the fd to the
>   	   application as is) */
>   	v4l2_fd_open(fd, 0);

Hmm, why are you removing this check ?

> diff --git a/lib/libv4lconvert/control/libv4lcontrol-priv.h b/lib/libv4lconvert/control/libv4lcontrol-priv.h
> index 22cdf34..1259e6b 100644
> --- a/lib/libv4lconvert/control/libv4lcontrol-priv.h
> +++ b/lib/libv4lconvert/control/libv4lcontrol-priv.h
> @@ -22,6 +22,8 @@
>   #ifndef __LIBV4LCONTROL_PRIV_H
>   #define __LIBV4LCONTROL_PRIV_H
>
> +#include "libv4l2-plugin.h"
> +
>   #define V4LCONTROL_SHM_SIZE 4096
>
>   #define V4LCONTROL_SUPPORTS_NEXT_CTRL 0x01
> @@ -37,6 +39,8 @@ struct v4lcontrol_data {
>   	unsigned int *shm_values; /* shared memory control value store */
>   	unsigned int old_values[V4LCONTROL_COUNT]; /* for controls_changed() */
>   	const struct v4lcontrol_flags_info *flags_info;
> +	struct libv4l2_dev_ops *dev_ops;
> +	void *dev_ops_priv;
>   };
>
>   struct v4lcontrol_flags_info {
> diff --git a/lib/libv4lconvert/control/libv4lcontrol.c b/lib/libv4lconvert/control/libv4lcontrol.c
> index 6a09d38..2ef642c 100644
> --- a/lib/libv4lconvert/control/libv4lcontrol.c
> +++ b/lib/libv4lconvert/control/libv4lcontrol.c
> @@ -701,7 +701,8 @@ static void v4lcontrol_get_flags_from_db(struct v4lcontrol_data *data,
>   		}
>   }
>
> -struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
> +struct v4lcontrol_data *v4lcontrol_create(int fd, void *dev_ops_priv,
> +		struct libv4l2_dev_ops *dev_ops, int always_needs_conversion)
>   {
>   	int shm_fd;
>   	int i, rc, got_usb_ids, init = 0;
> @@ -721,10 +722,12 @@ struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
>   	}
>
>   	data->fd = fd;
> +	data->dev_ops = dev_ops;
> +	data->dev_ops_priv = dev_ops_priv;
>
>   	/* Check if the driver has indicated some form of flipping is needed */
> -	if ((SYS_IOCTL(data->fd, VIDIOC_G_INPUT,&input.index) == 0)&&
> -			(SYS_IOCTL(data->fd, VIDIOC_ENUMINPUT,&input) == 0)) {
> +	if ((data->dev_ops->ioctl(data->dev_ops_priv, data->fd, VIDIOC_G_INPUT,&input.index) == 0)&&
> +			(data->dev_ops->ioctl(data->dev_ops_priv, data->fd, VIDIOC_ENUMINPUT,&input) == 0)) {
>   		if (input.status&  V4L2_IN_ST_HFLIP)
>   			data->flags |= V4LCONTROL_HFLIPPED;
>   		if (input.status&  V4L2_IN_ST_VFLIP)
> @@ -741,7 +744,8 @@ struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
>   		data->flags = strtol(s, NULL, 0);
>
>   	ctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
> -	if (SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL,&ctrl) == 0)
> +	if (data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +			VIDIOC_QUERYCTRL,&ctrl) == 0)
>   		data->priv_flags |= V4LCONTROL_SUPPORTS_NEXT_CTRL;
>
>   	/* If the device always needs conversion, we can add fake controls at no cost
> @@ -749,7 +753,8 @@ struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
>   	if (always_needs_conversion || v4lcontrol_needs_conversion(data)) {
>   		for (i = 0; i<  V4LCONTROL_AUTO_ENABLE_COUNT; i++) {
>   			ctrl.id = fake_controls[i].id;
> -			rc = SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL,&ctrl);
> +			rc = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +					VIDIOC_QUERYCTRL,&ctrl);
>   			if (rc == -1 || (rc == 0&&  (ctrl.flags&  V4L2_CTRL_FLAG_DISABLED)))
>   				data->controls |= 1<<  i;
>   		}
> @@ -761,17 +766,20 @@ struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
>   	   different sensors with / without autogain or the necessary controls. */
>   	while (data->flags&  V4LCONTROL_WANTS_AUTOGAIN) {
>   		ctrl.id = V4L2_CID_AUTOGAIN;
> -		rc = SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL,&ctrl);
> +		rc = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +				VIDIOC_QUERYCTRL,&ctrl);
>   		if (rc == 0&&  !(ctrl.flags&  V4L2_CTRL_FLAG_DISABLED))
>   			break;
>
>   		ctrl.id = V4L2_CID_EXPOSURE;
> -		rc = SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL,&ctrl);
> +		rc = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +				VIDIOC_QUERYCTRL,&ctrl);
>   		if (rc != 0 || (ctrl.flags&  V4L2_CTRL_FLAG_DISABLED))
>   			break;
>
>   		ctrl.id = V4L2_CID_GAIN;
> -		rc = SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL,&ctrl);
> +		rc = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +				VIDIOC_QUERYCTRL,&ctrl);
>   		if (rc != 0 || (ctrl.flags&  V4L2_CTRL_FLAG_DISABLED))
>   			break;
>
> @@ -788,7 +796,7 @@ struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion)
>   	if (data->controls == 0)
>   		return data; /* No need to create a shared memory segment */
>
> -	if (SYS_IOCTL(fd, VIDIOC_QUERYCAP,&cap)) {
> +	if (data->dev_ops->ioctl(data->dev_ops_priv, fd, VIDIOC_QUERYCAP,&cap)) {
>   		perror("libv4lcontrol: error querying device capabilities");
>   		goto error;
>   	}
> @@ -974,7 +982,8 @@ int v4lcontrol_vidioc_queryctrl(struct v4lcontrol_data *data, void *arg)
>   		}
>
>   	/* find out what the kernel driver would respond. */
> -	retval = SYS_IOCTL(data->fd, VIDIOC_QUERYCTRL, arg);
> +	retval = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +			VIDIOC_QUERYCTRL, arg);
>
>   	if ((data->priv_flags&  V4LCONTROL_SUPPORTS_NEXT_CTRL)&&
>   			(orig_id&  V4L2_CTRL_FLAG_NEXT_CTRL)) {
> @@ -1011,7 +1020,8 @@ int v4lcontrol_vidioc_g_ctrl(struct v4lcontrol_data *data, void *arg)
>   			return 0;
>   		}
>
> -	return SYS_IOCTL(data->fd, VIDIOC_G_CTRL, arg);
> +	return data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +			VIDIOC_G_CTRL, arg);
>   }
>
>   int v4lcontrol_vidioc_s_ctrl(struct v4lcontrol_data *data, void *arg)
> @@ -1032,7 +1042,8 @@ int v4lcontrol_vidioc_s_ctrl(struct v4lcontrol_data *data, void *arg)
>   			return 0;
>   		}
>
> -	return SYS_IOCTL(data->fd, VIDIOC_S_CTRL, arg);
> +	return data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +			VIDIOC_S_CTRL, arg);
>   }
>
>   int v4lcontrol_get_flags(struct v4lcontrol_data *data)
> diff --git a/lib/libv4lconvert/control/libv4lcontrol.h b/lib/libv4lconvert/control/libv4lcontrol.h
> index 974e97a..1c09546 100644
> --- a/lib/libv4lconvert/control/libv4lcontrol.h
> +++ b/lib/libv4lconvert/control/libv4lcontrol.h
> @@ -22,6 +22,8 @@
>   #ifndef __LIBV4LCONTROL_H
>   #define __LIBV4LCONTROL_H
>
> +#include "libv4l2-plugin.h"
> +
>   /* Flags */
>   #define V4LCONTROL_HFLIPPED              0x01
>   #define V4LCONTROL_VFLIPPED              0x02
> @@ -47,7 +49,8 @@ enum {
>
>   struct v4lcontrol_data;
>
> -struct v4lcontrol_data *v4lcontrol_create(int fd, int always_needs_conversion);
> +struct v4lcontrol_data *v4lcontrol_create(int fd, void *dev_ops_priv,
> +		struct libv4l2_dev_ops *dev_ops, int always_needs_conversion);
>   void v4lcontrol_destroy(struct v4lcontrol_data *data);
>
>   /* Functions used by v4lprocessing to get the control state */
> diff --git a/lib/libv4lconvert/libv4lconvert-priv.h b/lib/libv4lconvert/libv4lconvert-priv.h
> index d8fe899..edc118b 100644
> --- a/lib/libv4lconvert/libv4lconvert-priv.h
> +++ b/lib/libv4lconvert/libv4lconvert-priv.h
> @@ -65,6 +65,8 @@ struct v4lconvert_data {
>   	unsigned char *convert_pixfmt_buf;
>   	struct v4lcontrol_data *control;
>   	struct v4lprocessing_data *processing;
> +	struct libv4l2_dev_ops *dev_ops;
> +	void *dev_ops_priv;
>
>   	/* Data for external decompression helpers code */
>   	pid_t decompress_pid;
> diff --git a/lib/libv4lconvert/libv4lconvert.c b/lib/libv4lconvert/libv4lconvert.c
> index 0d8b29f..f6e0327 100644
> --- a/lib/libv4lconvert/libv4lconvert.c
> +++ b/lib/libv4lconvert/libv4lconvert.c
> @@ -91,7 +91,8 @@ static const int v4lconvert_crop_res[][2] = {
>   	{ 176, 144 },
>   };
>
> -struct v4lconvert_data *v4lconvert_create(int fd)
> +struct v4lconvert_data *v4lconvert_create(int fd, void *dev_ops_priv,
> +		struct libv4l2_dev_ops *dev_ops)
>   {
>   	int i, j;
>   	struct v4lconvert_data *data = calloc(1, sizeof(struct v4lconvert_data));
> @@ -107,6 +108,8 @@ struct v4lconvert_data *v4lconvert_create(int fd)
>   	}
>
>   	data->fd = fd;
> +	data->dev_ops = dev_ops;
> +	data->dev_ops_priv = dev_ops_priv;
>   	data->decompress_pid = -1;
>
>   	/* Check supported formats */
> @@ -115,7 +118,7 @@ struct v4lconvert_data *v4lconvert_create(int fd)
>
>   		fmt.index = i;
>
> -		if (SYS_IOCTL(data->fd, VIDIOC_ENUM_FMT,&fmt))
> +		if (data->dev_ops->ioctl(data->dev_ops_priv, data->fd, VIDIOC_ENUM_FMT,&fmt))
>   			break;
>
>   		for (j = 0; j<  ARRAY_SIZE(supported_src_pixfmts); j++)
> @@ -134,7 +137,8 @@ struct v4lconvert_data *v4lconvert_create(int fd)
>   	data->no_formats = i;
>
>   	/* Check if this cam has any special flags */
> -	if (SYS_IOCTL(data->fd, VIDIOC_QUERYCAP,&cap) == 0) {
> +	if (data->dev_ops->ioctl(data->dev_ops_priv,
> +					data->fd, VIDIOC_QUERYCAP,&cap) == 0) {
>   		if (!strcmp((char *)cap.driver, "uvcvideo"))
>   			data->flags |= V4LCONVERT_IS_UVC;
>
> @@ -142,7 +146,8 @@ struct v4lconvert_data *v4lconvert_create(int fd)
>   			always_needs_conversion = 0;
>   	}
>
> -	data->control = v4lcontrol_create(fd, always_needs_conversion);
> +	data->control = v4lcontrol_create(fd, dev_ops_priv, dev_ops,
> +						always_needs_conversion);
>   	if (!data->control) {
>   		free(data);
>   		return NULL;
> @@ -205,7 +210,8 @@ int v4lconvert_enum_fmt(struct v4lconvert_data *data, struct v4l2_fmtdesc *fmt)
>   	if (fmt->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>   			(!v4lconvert_supported_dst_fmt_only(data)&&
>   			fmt->index<  data->no_formats))
> -		return SYS_IOCTL(data->fd, VIDIOC_ENUM_FMT, fmt);
> +		return data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +						VIDIOC_ENUM_FMT, fmt);
>
>   	for (i = 0; i<  ARRAY_SIZE(supported_dst_pixfmts); i++)
>   		if (v4lconvert_supported_dst_fmt_only(data) ||
> @@ -313,7 +319,8 @@ static int v4lconvert_do_try_format(struct v4lconvert_data *data,
>   		try_fmt = *dest_fmt;
>   		try_fmt.fmt.pix.pixelformat = supported_src_pixfmts[i].fmt;
>
> -		if (!SYS_IOCTL(data->fd, VIDIOC_TRY_FMT,&try_fmt)) {
> +		if (!data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +						VIDIOC_TRY_FMT,&try_fmt)) {
>   			if (try_fmt.fmt.pix.pixelformat == supported_src_pixfmts[i].fmt) {
>   				int size_x_diff = abs((int)try_fmt.fmt.pix.width -
>   						(int)dest_fmt->fmt.pix.width);
> @@ -381,7 +388,8 @@ int v4lconvert_try_format(struct v4lconvert_data *data,
>   	if (!v4lconvert_supported_dst_format(dest_fmt->fmt.pix.pixelformat) ||
>   			dest_fmt->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>   			v4lconvert_do_try_format(data,&try_dest,&try_src)) {
> -		result = SYS_IOCTL(data->fd, VIDIOC_TRY_FMT, dest_fmt);
> +		result = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +							VIDIOC_TRY_FMT, dest_fmt);
>   		if (src_fmt)
>   			*src_fmt = *dest_fmt;
>   		return result;
> @@ -1236,7 +1244,8 @@ static void v4lconvert_get_framesizes(struct v4lconvert_data *data,
>
>   	for (i = 0; ; i++) {
>   		frmsize.index = i;
> -		if (SYS_IOCTL(data->fd, VIDIOC_ENUM_FRAMESIZES,&frmsize))
> +		if (data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +					VIDIOC_ENUM_FRAMESIZES,&frmsize))
>   			break;
>
>   		/* We got a framesize, check we don't have the same one already */
> @@ -1296,7 +1305,8 @@ int v4lconvert_enum_framesizes(struct v4lconvert_data *data,
>   			errno = EINVAL;
>   			return -1;
>   		}
> -		return SYS_IOCTL(data->fd, VIDIOC_ENUM_FRAMESIZES, frmsize);
> +		return data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +						VIDIOC_ENUM_FRAMESIZES, frmsize);
>   	}
>
>   	if (frmsize->index>= data->no_framesizes) {
> @@ -1332,7 +1342,8 @@ int v4lconvert_enum_frameintervals(struct v4lconvert_data *data,
>   			errno = EINVAL;
>   			return -1;
>   		}
> -		res = SYS_IOCTL(data->fd, VIDIOC_ENUM_FRAMEINTERVALS, frmival);
> +		res = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +				VIDIOC_ENUM_FRAMEINTERVALS, frmival);
>   		if (res)
>   			V4LCONVERT_ERR("%s\n", strerror(errno));
>   		return res;
> @@ -1377,7 +1388,8 @@ int v4lconvert_enum_frameintervals(struct v4lconvert_data *data,
>   	frmival->pixel_format = src_fmt.fmt.pix.pixelformat;
>   	frmival->width = src_fmt.fmt.pix.width;
>   	frmival->height = src_fmt.fmt.pix.height;
> -	res = SYS_IOCTL(data->fd, VIDIOC_ENUM_FRAMEINTERVALS, frmival);
> +	res = data->dev_ops->ioctl(data->dev_ops_priv, data->fd,
> +			VIDIOC_ENUM_FRAMEINTERVALS, frmival);
>   	if (res) {
>   		int dest_pixfmt = dest_fmt.fmt.pix.pixelformat;
>   		int src_pixfmt  = src_fmt.fmt.pix.pixelformat;