Change Details

Notify applications that a device is unavailable/unregistered instead of skipping it. The current implementations of SNDCTL_AUDIOINFO, SNDCTL_MIXERINFO and SNDCTL_CARDINFO break applications that expect to get information about a device that is skipped. PR: 277615 Sponsored by: The FreeBSD Foundation MFC after: 3 days

mixer(8)'s -a option is used to print information about all mixer devices in the system. To do this, it loops from 0 to mixer_get_nmixers(), and tries to open "/dev/mixer%d". However, this approach doesn't work when there are disabled/unregistered mixers in the system, or when an audio device simply doesn't have a mixer. mixer_get_nmixers() calls SNDCTL_SYSINFO and returns oss_sysinfo->nummixers, whose value is the number of currently _enabled_ mixers only. Taking the bug report mentioned below (277615) as an example, suppose a system with 8 mixer devices total, but 3 of them are either disabled or non-existent, which means they will not show up under /dev, meaning we have 5 enabled mixer devices, which is also what the value of oss_sysinfo->nummixers will be. What mixer(8) will do is loop from 0 to 5 (instead of 8), and start calling mixer_open() on /dev/mixer0, up to /dev/mixer4, and as is expected, the first call will fail right away, hence the error shown in the bug report. To fix this, modify oss_sysinfo->nummixers to hold the value of the maximum unit in the system, which, although not necessarily "correct", is more intuitive for applications that will want to use this value to loop through all mixer devices. Additionally, notify applications that a device is unavailable/unregistered instead of skipping it. The current implementations of SNDCTL_AUDIOINFO, SNDCTL_MIXERINFO and SNDCTL_CARDINFO break applications that expect to get information about a device that is skipped. Related discussion can be found here: https://reviews.freebsd.org/D45135#1029526 It has to be noted, that other applications, apart from mixer(8), suffer from this. PR: 277615 Sponsored by: The FreeBSD Foundation MFC after: 3 days

Notify applicamixer(8)'s -a options that a device is unavailable/unregistered instead of is used to print information about all mixer skipping it.devices in the system. To do this, The current implementations of SNDCTL_AUDIOINFO,it loops from 0 to SNDCTL_MIXERINFOmixer_get_nmixers(), and SNDCTL_CARDINFO break applications that expect totries to open "/dev/mixer%d". However, this get information about a device that is skippedapproach doesn't work when there are disabled/unregistered mixers in the system, or when an audio device simply doesn't have a mixer. mixer_get_nmixers() calls SNDCTL_SYSINFO and returns oss_sysinfo->nummixers, whose value is the number of currently _enabled_ mixers only. Taking the bug report mentioned below (277615) as an example, suppose a system with 8 mixer devices total, but 3 of them are either disabled or non-existent, which means they will not show up under /dev, meaning we have 5 enabled mixer devices, which is also what the value of oss_sysinfo->nummixers will be. What mixer(8) will do is loop from 0 to 5 (instead of 8), and start calling mixer_open() on /dev/mixer0, up to /dev/mixer4, and as is expected, the first call will fail right away, hence the error shown in the bug report. To fix this, modify oss_sysinfo->nummixers to hold the value of the maximum unit in the system, which, although not necessarily "correct", is more intuitive for applications that will want to use this value to loop through all mixer devices. Additionally, notify applications that a device is unavailable/unregistered instead of skipping it. The current implementations of SNDCTL_AUDIOINFO, SNDCTL_MIXERINFO and SNDCTL_CARDINFO break applications that expect to get information about a device that is skipped. Related discussion can be found here: https://reviews.freebsd.org/D45135#1029526 It has to be noted, that other applications, apart from mixer(8), suffer from this. PR: 277615 Sponsored by: The FreeBSD Foundation MFC after: 3 days