Uncorrect behaviour of SDL-audio when asked to do conversion runtime while playing

As I pointed out on SDL bugzilla
audio is not behaving correctly when the conversion of sound stream
require more samples on output then the one that are incoming. While
there is actually a bug on SDL, I wonder what should be the number of
samples agreed between user and SDL (and actually the driver), when the
agreed sound rate is not the one asked from the client:
I ask for 11025 sample/sec and number of samples 512
If sound driver accept only a 48000 sample/sec, should SDL ask the
driver if it accepts 512 * 48000 / 11025 and report back the scaled
value to the application or what?