[LAU] Sound Devices USBPre2, UAC2 status

[alexander]

On 24/01/13 23:40, shal at free.fr wrote:
>
> ----- Mail original -----
>> De: "alexander" <axeldenstore at gmail.com>
>> À: linux-audio-user at lists.linuxaudio.org
>> Envoyé: Lundi 21 Janvier 2013 15:58:55
>> Objet: Re: [LAU] Sound Devices USBPre2, UAC2 status
>> Oliver check your SD thread
>> http://forum.sounddevices.com/showthread.php?3785-Linux-status-for-usbPre2&highlight=linux
>> Paul Isaacs of Sound Devices has posted a potentially helpful reply!
>
> Hi,
>
> I have some succes on UAC2 support for the USBPRe2.
>
> Like indicated by Paul form Sound Devices, the sound card recognize that the OS is a Windows and so only have one configuration descriptor in the device desciptor : the UAC1 descriptor. The used method is on the STANDARD_REQUEST_GET_DESCRIPTOR if the wLength is 64 the OS is supposed to be Windows.
>
> But Linux have taken the same behavior like of Windows and take also the 64 value.
> In  driver/usb/core/hub.c : #define GET_DESCRIPTOR_BUFSIZE 64
>
> If you put another value (like 65) the device descriptor have now 2 configuration descriptor (UAC1 and UAC2).
> It seems mandatory to have a unplug/plug of the sound card (the first "get_descriptor" seems to determine the sound card behavior).
>
>
> My "lsusb -v -d 0926:" : http://pastebin.com/nFTN2E04
>
>
> First step is OK.
> Nevertheless, the sound card remains in UAC1.
> The kernel choose the first valid configuration descriptor and the UAC1 is OK so....
>
> I have test a ugly patch.
> At the end of the function usb_choose_configuration() (in file driver/usb/core/generic.c) , I changed the behavior like this:
> if(udev->product != NULL)
>    if(strlen(udev->product) >= 7)
>     if(strncmp(udev->product,"USBPre2",7) == 0)
>      {
>      i++;
>      printk("USBPre2: overwrite the choosen configuration to the follower :%d\n",i);
>     }
> return i;
>
> And that all, now the USBPRe2 is view as a UAC2 sound card.
>
> I have played a 24bit/192khz music.
> This is the status of the sound card:
>
> $ cat /proc/asound/USBPre2/stream0
> Sound Devices USBPre2 at usb-0000:00:1d.0-1.3, high speed : USB Audio
>
> Playback:
> Status: Running
> Interface = 1
> Altset = 2
> Packet Size = 156
> Momentary freq = 192000 Hz (0x18.0000)
> Feedback Format = 8.16
> Packet Size = 0
> Momentary freq = 192000 Hz (0x18.0000)
> Interface 1
> Altset 1
> Format: S16_LE
> Channels: 2
> Endpoint: 6 OUT (ASYNC)
> Rates: 8000, 16000, 24000, 32000, 44100, 48000, 88200, 96000, 176400, 192000
> Data packet interval: 125 us
> Interface 1
> Altset 2
> Format: S24_3LE
> Channels: 2
> Endpoint: 6 OUT (ASYNC)
> Rates: 8000, 16000, 24000, 32000, 44100, 48000, 88200, 96000, 176400, 192000
> Data packet interval: 125 us
>
>
> Jackd is OK with "/usr/bin/jackd -P10 -p128 -dalsa -dhw:0 -r192000 -p2048 -n3 -m -H -M -P"
>
> It's remains a problem : I am not able to performs a capture....
>
> So, I hope that this information will permit to find a way to have a easy and complete UAC2 support for this sound card.
>
> Bye
> Olivier
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wondeful! I hope this gets resolved quickly!