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Subject[patch] videodev fixups / generic usercopy helper
  Hi,

I've just noticed that a hole left in the recent changes which should
allow the usb v4l drivers to unregister with open file handles. The
drivers itself handle it just fine, but video_generic_ioctl() will barf
when called on unregistered devices. Oops.

One way to fix this is to expect drivers call the helper function and
pass a pointer for the function doing the actual work, i.e. handle it
this way:

driver_ioctl(inode,file,cmd,userptr)
-> video_usercopy(inode,file,cmd,userptr,func)
copy_from_user(...)
-> func(inode,file,cmd,kernelptr);
copy_to_user(...)

Patch against 2.5.7-pre2 below. It updates videodev.[ch] and adapts
usbvideo.c to show how the driver changes will look like.

Note that this change makes the usercopy helper function a very generic
one, it probably could be used for other drivers to (as long as the API
has sane magic numbers based on _IO*(...) defines) as there is no
video4linux-related stuff in there any more. So we might think of
renaming it an moving it to some more central place (fs/ioctl.c maybe).

Comments?

Gerd

==============================[ cut here ]==============================
===== drivers/media/video/videodev.c 1.11 vs edited =====
--- 1.11/drivers/media/video/videodev.c Fri Mar 8 13:42:38 2002
+++ edited/drivers/media/video/videodev.c Mon Mar 18 09:55:26 2002
@@ -107,20 +107,18 @@
}

/*
- * ioctl helper function -- handles userspace copying
+ * helper function -- handles userspace copying for ioctl arguments
*/
int
-video_generic_ioctl(struct inode *inode, struct file *file,
- unsigned int cmd, unsigned long arg)
+video_usercopy(struct inode *inode, struct file *file,
+ unsigned int cmd, unsigned long arg,
+ int (*func)(struct inode *inode, struct file *file,
+ unsigned int cmd, void *arg))
{
- struct video_device *vfl = video_devdata(file);
char sbuf[128];
void *mbuf = NULL;
void *parg = NULL;
int err = -EINVAL;
-
- if (vfl->kernel_ioctl == NULL)
- return -EINVAL;

/* Copy arguments into temp kernel buffer */
switch (_IOC_DIR(cmd)) {
@@ -147,7 +145,7 @@
}

/* call driver */
- err = vfl->kernel_ioctl(inode, file, cmd, parg);
+ err = func(inode, file, cmd, parg);
if (err == -ENOIOCTLCMD)
err = -EINVAL;
if (err < 0)
@@ -512,7 +510,7 @@
EXPORT_SYMBOL(video_register_device);
EXPORT_SYMBOL(video_unregister_device);
EXPORT_SYMBOL(video_devdata);
-EXPORT_SYMBOL(video_generic_ioctl);
+EXPORT_SYMBOL(video_usercopy);
EXPORT_SYMBOL(video_exclusive_open);
EXPORT_SYMBOL(video_exclusive_release);

===== drivers/usb/usbvideo.c 1.13 vs edited =====
--- 1.13/drivers/usb/usbvideo.c Fri Mar 8 13:42:42 2002
+++ edited/drivers/usb/usbvideo.c Mon Mar 18 09:53:46 2002
@@ -1020,7 +1020,7 @@
release: usbvideo_v4l_close,
read: usbvideo_v4l_read,
mmap: usbvideo_v4l_mmap,
- ioctl: video_generic_ioctl,
+ ioctl: usbvideo_v4l_ioctl,
llseek: no_llseek,
};
static struct video_device usbvideo_template = {
@@ -1028,7 +1028,6 @@
type: VID_TYPE_CAPTURE,
hardware: VID_HARDWARE_CPIA,
fops: &usbvideo_fops,
- kernel_ioctl: usbvideo_v4l_ioctl,
};

uvd_t *usbvideo_AllocateDevice(usbvideo_t *cams)
@@ -1349,8 +1348,8 @@
* History:
* 22-Jan-2000 Corrected VIDIOCSPICT to reject unsupported settings.
*/
-int usbvideo_v4l_ioctl(struct inode *inode, struct file *file,
- unsigned int cmd, void *arg)
+static int usbvideo_v4l_do_ioctl(struct inode *inode, struct file *file,
+ unsigned int cmd, void *arg)
{
uvd_t *uvd = file->private_data;

@@ -1553,6 +1552,12 @@
return -ENOIOCTLCMD;
}
return 0;
+}
+
+int usbvideo_v4l_ioctl(struct inode *inode, struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ return video_usercopy(inode, file, cmd, arg, usbvideo_v4l_do_ioctl);
}

/*
===== drivers/usb/usbvideo.h 1.8 vs edited =====
--- 1.8/drivers/usb/usbvideo.h Fri Mar 8 13:59:09 2002
+++ edited/drivers/usb/usbvideo.h Mon Mar 18 09:57:14 2002
@@ -350,7 +350,7 @@
int usbvideo_v4l_close(struct inode *inode, struct file *file);
int usbvideo_v4l_initialize(struct video_device *dev);
int usbvideo_v4l_ioctl(struct inode *inode, struct file *file,
- unsigned int ioctlnr, void *arg);
+ unsigned int cmd, unsigned long arg);
int usbvideo_v4l_mmap(struct file *file, struct vm_area_struct *vma);
int usbvideo_v4l_open(struct inode *inode, struct file *file);
int usbvideo_v4l_read(struct file *file, char *buf,
===== include/linux/videodev.h 1.12 vs edited =====
--- 1.12/include/linux/videodev.h Fri Mar 8 13:42:38 2002
+++ edited/include/linux/videodev.h Mon Mar 18 09:55:52 2002
@@ -37,8 +37,6 @@
* video_generic_ioctl() does the userspace copying of the
* ioctl arguments */
struct file_operations *fops;
- int (*kernel_ioctl)(struct inode *inode, struct file *file,
- unsigned int cmd, void *arg);
void *priv; /* Used to be 'private' but that upsets C++ */

/* for videodev.c intenal usage -- don't touch */
@@ -60,8 +58,10 @@

extern int video_exclusive_open(struct inode *inode, struct file *file);
extern int video_exclusive_release(struct inode *inode, struct file *file);
-extern int video_generic_ioctl(struct inode *inode, struct file *file,
- unsigned int cmd, unsigned long arg);
+extern int video_usercopy(struct inode *inode, struct file *file,
+ unsigned int cmd, unsigned long arg,
+ int (*func)(struct inode *inode, struct file *file,
+ unsigned int cmd, void *arg));
#endif /* __KERNEL__ */

#define VID_TYPE_CAPTURE 1 /* Can capture */
-
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