Date: Tue, 05 May 2020 01:42:48 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 246206] dev/sound: SNDCTL_SYSINFO does not report PCM_CAP_VIRTUAL Message-ID: <bug-246206-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D246206 Bug ID: 246206 Summary: dev/sound: SNDCTL_SYSINFO does not report PCM_CAP_VIRTUAL Product: Base System Version: 12.1-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: kevinz5000@gmail.com Attachment #214136 text/plain mime type: Created attachment 214136 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D214136&action= =3Dedit Demonstration of issue In sys/soundcard.h, PCM_CAP_VIRTUAL is documented as "Virtual device": # define PCM_CAP_VIRTUAL 0x00040000 /* Virtual device */ When SNDCTL_AUDIOINFO is called on /dev/mixer, no virtual devices have have PCM_CAP_VIRTUAL set. This means, apart from being smart, consumers of the O= SS4 API can't tell virtual devices from real devices. This leads to a confusing choice in, say, audio programs that allow selection of vchans. A short example program that demonstrates the issue is attached. Example ou= tput on my computer is: $ clang vpctest.c -o vpctest $ ./vpctest dev /dev/dsp0.p0 virtual 0 dev /dev/dsp0.vp0 virtual 0 dev /dev/dsp0.vp1 virtual 0 dev /dev/dsp0.r0 virtual 0 dev /dev/dsp0.vr0 virtual 0 dev /dev/dsp0.vr1 virtual 0 The vp* and vr* devices are virtual, but PCM_CAP_VIRTUAL is not set. The root cause of this issue appears to be in dev/sound/pcm/dsp.c: ai->caps =3D PCM_CAP_REALTIME | PCM_CAP_MMAP | PCM_CAP_TRIGGER | CHANNEL_GETCAPS(ch) ((ch->direction =3D=3D PCMDIR_PLAY) ? PCM_CAP_OUTPUT : PCM_CAP_INPUT); Most notably, PCM_CAP_VIRTUAL is never set. Further, the channel capabiliti= es queried earlier: caps =3D chn_getcaps(ch); Do not appear to be used, either. I suggest that virtual channels return PCM_CAP_VIRTUAL in vchan_getcaps() (dev/sound/pcm/vchan.c), and then channel capabilities get OR'ed into ai->c= aps. --=20 You are receiving this mail because: You are the assignee for the bug.=
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