Open Sound System
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ioctl(fd, SNDCTL_DSP_GETODELAY, &delay):
The above code fragment lacks all error checks for clarity. Real world applications must always check for the errors and handle them as described below. Also most OSS ioctl calls will return information in the argument variable and it's usually necessary to check it too.
This call takes in account the FIFO delays caused by the device as much as it's possible. For this reason the returned value will normally not drop to zero or anywhere close of it (the application must not assume this). If the application stops writing to the device it will sooner or later cause a buffer underrun. OSS will recover from this situation by appending some silent samples to the buffer.
Please look at the When OSS audio ioctl calls can be made section for information about DSP ioctl call ordering.
The return value from the OSS ioctl calls will be -1 if a fatal error occurred. Other values mean that the ioctl call was more or less successful. However in most cases the application must check the value returned in the argument to see what was the accepted value.
Please see the Possible error codes (errno) returned by OSS calls section for more info about the error codes returned by OSS.
|osstest.c||The osstest program shipped with OSS|
|fulldup.c||Full duplex sample program using the single device approach.|
|ioctl_test.c||This program has been used to verify that some of the ioctl calls work|