diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt index 51a7b6db118f..df0247ed13d8 100644 --- a/Documentation/video4linux/v4l2-framework.txt +++ b/Documentation/video4linux/v4l2-framework.txt @@ -91,7 +91,8 @@ NULL, then you *must* setup v4l2_dev->name before calling v4l2_device_register. The first 'dev' argument is normally the struct device pointer of a pci_dev, usb_device or platform_device. It is rare for dev to be NULL, but it happens -with ISA devices, for example. +with ISA devices or when one device creates multiple PCI devices, thus making +it impossible to associate v4l2_dev with a particular parent. You unregister with: @@ -414,6 +415,15 @@ You should also set these fields: - ioctl_ops: if you use the v4l2_ioctl_ops to simplify ioctl maintenance (highly recommended to use this and it might become compulsory in the future!), then set this to your v4l2_ioctl_ops struct. +- parent: you only set this if v4l2_device was registered with NULL as + the parent device struct. This only happens in cases where one hardware + device has multiple PCI devices that all share the same v4l2_device core. + + The cx88 driver is an example of this: one core v4l2_device struct, but + it is used by both an raw video PCI device (cx8800) and a MPEG PCI device + (cx8802). Since the v4l2_device cannot be associated with a particular + PCI device it is setup without a parent device. But when the struct + video_device is setup you do know which parent PCI device to use. If you use v4l2_ioctl_ops, then you should set either .unlocked_ioctl or .ioctl to video_ioctl2 in your v4l2_file_operations struct. |