On Tue, 14 Aug 2018 18:25:15 +0200, Rob Duncan wrote:
Hi Takashi,
- Should the poll FD be made writeable as soon as data is available, or only when at least avail_min is available?
The latter. Again, ioplug emulates the hardware driver, so the poll should behave same as the hardware driver does. (Though, admittedly, not all plugin implementations follow this strictly....)
So, the poll FD must be readable while there is at least avail_min in the buffer, and must NOT be readable if there is less than avail_min. Is that right?
Yes.
To labor the point a bit, if exactly avail_min becomes available the poll FD must be made readable. If a single frame is now transferred, so the buffer has (avail_min - 1) available, what must the state of the poll FD be?
The driver sipmly doesn't set POLLIN|POLLRDNORM bits (or POLLOUT|POLLWRNORM) unless avail >= avail_min.
A couple more questions:
If we are configured to do blocking operations must the read and write callbacks always transfer the full requested size, or can they do partial transfers?
In general, a partial transfer is always allowed no matter whether blocking or non-blocking mode is.
Takashi
On the other hand, what if we are configured to do non-blocking operations?
Or does the caller guarantee not to request a transfer larger than what the ioplugin reports as available?
Thanks,
Rob.