Yair K. wrote: > > At the moment, the only way I know of to discover whether new control have > been added with the current API is to poll the device for total number of > mixers (via SNDCTL_MIX_NREXT) and to compare this to the previous number > (this is what ossxmix does for VMIX). If so, than the groups may be > ignored/throwed away and it won't matter. > > (BTW, If controls can also be removed, and not just added, than there's an > edge case: > A. Total number can be the same even in a case of change. (1-1=0) > B. ossxmix polls the controls, if all the newly added mixers have the same > control numbers than get_value won't fail and the display won't be reloaded. > > Not sure how to really fix this: A separate flag in SNDCTL_MIXERINFO to > inform of such changes? Or maybe changing a group's modify_counter in > SNDCTL_MIX_EXTINFO?) > SNDCTL_MIX_NREXT cannot be used to detect this kind of situation. However the timestamp field of SNDCTL_MIX_READ/WRITE will trigger error (errno=EIDRM) if the control has been recreated.
Maybe group's update_counter could be used to return the number of controls located inside the group and it's sub groups. Every time a new control is added the mixer core will increment the update_counter for the parent groups (up to the root). In this way ossxmix can find out if the group is empty or not simply by looking if update_counter>0. Best regards, Hannu _______________________________________________ oss-devel mailing list oss-devel@mailman.opensound.com http://mailman.opensound.com/mailman/listinfo/oss-devel
