Dne 20. 01. 21 v 10:27 Takashi Iwai napsal(a): > On Wed, 20 Jan 2021 09:55:41 +0100, > Takashi Sakamoto wrote: >> >> ALSA control core allows usespace application to register control element >> set by call of ioctl(2) with SNDRV_CTL_IOCTL_ELEM_ADD request. The added >> control element set is called as 'user-defined'. Currently sound card has >> limitation on the number of the user-defined control element set up >> to 32. >> >> The limitation is inconvenient to drivers in ALSA firewire stack since >> the drivers expect userspace applications to implement function to >> control device functionalities such as mixing and routing. As the >> userspace application, snd-firewire-ctl-services project starts: >> https://github.com/alsa-project/snd-firewire-ctl-services/ >> >> The project supports many devices supported by ALSA firewire stack. The >> limitation is mostly good since routing and mixing controls can be >> represented by control element set, which includes control element with >> the same parameters. Nevertheless, it's actually inconvenient to device >> which has many varied functionalities. For example, plugin effect such as >> channel strip and reverb has many parameters. For the case, many control >> elements are required to configure the parameters and control element set >> cannot aggregates controls for the parameters. At present, below models >> are implemented with the control elements and actually add control element >> sets over 32: >> >> * Apogee Emsemble (snd-bebob-ctl-service) >> * TC Electronic Konnekt 24d (snd-dice-ctl-service) >> * TC Electronic Studio Konnekt 48 (snd-dice-ctl-service) >> * TC Electronic Konnekt Live (snd-dice-ctl-service) >> * TC Electronic Impact Twin (snd-dice-ctl-service) >> >> It could be investigated to increase the number; e.g. quadruple to the >> current (=128), however it's hard to find criteria about the number for >> existent sound card. This commit just removes the limitation for the >> reason. ALSA control core uses UINT_MAX as the maximum number of control >> elements added to a sound card. It's limitation for both in-kernel driver >> and userspace application. >> >> Signed-off-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx> > > I'm still worried by the unlimited number of possible additions. > Did you check what would happen if you run a test program to add > user-space ctls (with the max count) in a loop repeatedly? If that > doesn't blow up too much, it might be OK. Otherwise we have to add > some practical limits. > > So, let's prove that it's absolutely safe to release the limit at > first. I agree. The UINT_MAX limit is really big in my eyes. The condition was added to check for the insane allocations. I basically agree to increase this limit (512, 1024?), but it should not be UINT_MAX. Jaroslav -- Jaroslav Kysela <perex@xxxxxxxx> Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
