Re: [PATCH] usb-audio: Fix invalid values in AudioControl descriptors

[Volker Rümelin]

Am 09.03.24 um 18:29 schrieb Joonas Kankaala:
> This fixes the invalid bInterfaceProtocol value 0x04 in the USB audio
> AudioControl descriptors. It should be zero. While Linux and Windows
> forgive this error, macOS 14 Sonoma does not. The usb-audio device does
> not appear in macOS sound settings even though the device is recognized
> and shows up in USB system information. According to the USB audio class
> specs 1.0-4.0, valid values are 0x00, 0x20, 0x30 and 0x40. (Note also
> that Linux prints the warning "unknown interface protocol 0x4, assuming
> v1", but then proceeds as if the value was zero.)
>
> This also fixes the invalid wTotalLength value in the multi-channel
> setup AudioControl interface header descriptor (used when multi=on
> and out.mixing-engine off). The combined length of all the descriptors
> there add up to 0x37, not 0x38. In Linux, "lsusb -D ..." displays
> incomplete descriptor information when this length is incorrect.
>
> Signed-off-by: Joonas Kankaala <joonas.a.kankaala@gmail.com>

lsusb also misinterprets the invalid interface protocol 0x4 and uses
0x30 instead.

Reviewed-by: Volker Rümelin <vr_qemu@t-online.de>

> ---
>  hw/usb/dev-audio.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/hw/usb/dev-audio.c b/hw/usb/dev-audio.c
> index d5ac1f8962..1897fff9e6 100644
> --- a/hw/usb/dev-audio.c
> +++ b/hw/usb/dev-audio.c
> @@ -124,7 +124,6 @@ static const USBDescIface desc_iface[] = {
>          .bNumEndpoints                 = 0,
>          .bInterfaceClass               = USB_CLASS_AUDIO,
>          .bInterfaceSubClass            = USB_SUBCLASS_AUDIO_CONTROL,
> -        .bInterfaceProtocol            = 0x04,
>          .iInterface                    = STRING_USBAUDIO_CONTROL,
>          .ndesc                         = 4,
>          .descs = (USBDescOther[]) {
> @@ -282,7 +281,6 @@ static const USBDescIface desc_iface_multi[] = {
>          .bNumEndpoints                 = 0,
>          .bInterfaceClass               = USB_CLASS_AUDIO,
>          .bInterfaceSubClass            = USB_SUBCLASS_AUDIO_CONTROL,
> -        .bInterfaceProtocol            = 0x04,
>          .iInterface                    = STRING_USBAUDIO_CONTROL,
>          .ndesc                         = 4,
>          .descs = (USBDescOther[]) {
> @@ -293,7 +291,7 @@ static const USBDescIface desc_iface_multi[] = {
>                      USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
>                      DST_AC_HEADER,              /*  u8  bDescriptorSubtype */
>                      U16(0x0100),                /* u16  bcdADC */
> -                    U16(0x38),                  /* u16  wTotalLength */
> +                    U16(0x37),                  /* u16  wTotalLength */
>                      0x01,                       /*  u8  bInCollection */
>                      0x01,                       /*  u8  baInterfaceNr */
>                  }