6.11. request ioctl()¶
6.11.1. Name¶
request-ioctl - Control a request file descriptor
6.11.3. Arguments¶
fd- File descriptor returned by ioctl MEDIA_IOC_REQUEST_ALLOC.
cmd- The request ioctl command code as defined in the media.h header file, for example ioctl MEDIA_REQUEST_IOC_QUEUE.
argp- Pointer to a request-specific structure.
6.11.4. Description¶
The ioctl() function manipulates request
parameters. The argument fd must be an open file descriptor.
The ioctl cmd code specifies the request function to be called. It
has encoded in it whether the argument is an input, output or read/write
parameter, and the size of the argument argp in bytes.
Macros and structures definitions specifying request ioctl commands and their parameters are located in the media.h header file. All request ioctl commands, their respective function and parameters are specified in Function Reference.
6.11.5. Return Value¶
On success 0 is returned, on error -1 and the errno variable is set
appropriately. The generic error codes are described at the
Generic Error Codes chapter.
Command-specific error codes are listed in the individual command descriptions.
When an ioctl that takes an output or read/write parameter fails, the parameter remains unmodified.