Re: [PATCH v2] usb: gadget: f_uac1: add interface association descriptor

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

On Wed, 2022-06-29 at 12:46 +0300, Ruslan Bilovol wrote:
>  On Wed, Jun 29, 2022 at 5:13 AM Chunfeng Yun <
> chunfeng.yun@mediatek.com> wrote:
> > 
> > From: xin lin <xin.lin@mediatek.com>
> > 
> > When we want to use a composite device that supports UVC, UAC1 and
> > ADB at the same time, encounter that UAC1 can't work when connected
> > to windows 10 system.
> > From the online documents of microsoft, "overview of enumeration of
> > interface collections on usb composite devices", it recommends that
> > vendors use IADs (interface association descriptor) to define
> > interface collections.
> > After addding IAD, we can fix the issue.
> 
> It is incorrect to add Interface Association Descriptor to the UAC1
> function.
> The UAC1 specification was developed much earlier than IAD was
> invented, and it
> implements this functionality in another way - by describing number
> of
> associated
> interfaces and interface numbers on Class-Specific AC Interface
> Descriptor level;
> see *bInCollection* and *baInterfaceNr* fields of UAC1 Class-Specific
> AC Interface
> Header Descriptor in 4.3.2 section of UAC1 specification.
> 
> This is already implemented in f_uac1.c (see where *bInCollection*
> and
> *baInterfaceNr*
> are updated), along with support of dynamic capture/playback
> endpoints
> enablement.
> Adding IAD to the UAC1 driver is duplicating that functionality and
> isn't supported
> by UAC1 spec.
Ok, seems win10 don't support this way.

Abandon this patch.

> 
> On the other hand, the USB orgcommittee switched the approach of
> interface collection
> definition from a class-specific descriptors level to IAD in the UAC2
> spec.
> So why not use UAC2 function for the same purpose, it already has IAD
> implemented
> and is supported by Win10?
unfortunately, also encounter enumeration issues on some versions of
win10.

Thanks

> 
> Thanks,
> Ruslan
> 
> > 
> > Signed-off-by: xin lin <xin.lin@mediatek.com>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> > ---
> > v2: modify commit log suggested by Greg
> > ---
> >  drivers/usb/gadget/function/f_uac1.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> > 
> > diff --git a/drivers/usb/gadget/function/f_uac1.c
> > b/drivers/usb/gadget/function/f_uac1.c
> > index 6f0e1d803dc2..8390207bc513 100644
> > --- a/drivers/usb/gadget/function/f_uac1.c
> > +++ b/drivers/usb/gadget/function/f_uac1.c
> > @@ -71,6 +71,17 @@ static inline struct f_uac1_opts
> > *g_audio_to_uac1_opts(struct g_audio *audio)
> >   * ALSA_Playback -> IT_3 -> OT_4 -> USB-IN
> >   */
> > 
> > +static struct usb_interface_assoc_descriptor iad_desc = {
> > +       .bLength = sizeof(iad_desc),
> > +       .bDescriptorType = USB_DT_INTERFACE_ASSOCIATION,
> > +
> > +       .bFirstInterface = 0,
> > +       .bInterfaceCount = 3,
> > +       .bFunctionClass = USB_CLASS_AUDIO,
> > +       .bFunctionSubClass = 0,
> > +       .bFunctionProtocol = UAC_VERSION_1,
> > +};
> > +
> >  /* B.3.1  Standard AC Interface Descriptor */
> >  static struct usb_interface_descriptor ac_interface_desc = {
> >         .bLength =              USB_DT_INTERFACE_SIZE,
> > @@ -259,6 +270,7 @@ static struct uac_iso_endpoint_descriptor
> > as_iso_in_desc = {
> >  };
> > 
> >  static struct usb_descriptor_header *f_audio_desc[] = {
> > +       (struct usb_descriptor_header *)&iad_desc,
> >         (struct usb_descriptor_header *)&ac_interface_desc,
> >         (struct usb_descriptor_header *)&ac_header_desc,
> > 
> > @@ -293,6 +305,7 @@ static struct usb_descriptor_header
> > *f_audio_desc[] = {
> >  };
> > 
> >  enum {
> > +       STR_ASSOC,
> >         STR_AC_IF,
> >         STR_USB_OUT_IT,
> >         STR_USB_OUT_IT_CH_NAMES,
> > @@ -310,6 +323,7 @@ enum {
> > 
> >  static struct usb_string strings_uac1[] = {
> >         /* [STR_AC_IF].s = DYNAMIC, */
> > +       [STR_ASSOC].s = "Source/Sink",
> >         [STR_USB_OUT_IT].s = "Playback Input terminal",
> >         [STR_USB_OUT_IT_CH_NAMES].s = "Playback Channels",
> >         [STR_IO_OUT_OT].s = "Playback Output terminal",
> > @@ -1058,6 +1072,7 @@ static void setup_descriptor(struct
> > f_uac1_opts *opts)
> >         as_out_header_desc.bTerminalLink =
> > usb_out_it_desc.bTerminalID;
> >         as_in_header_desc.bTerminalLink =
> > usb_in_ot_desc.bTerminalID;
> > 
> > +       iad_desc.bInterfaceCount = 1;
> >         ac_header_desc->wTotalLength = cpu_to_le16(ac_header_desc-
> > >bLength);
> > 
> >         if (EPIN_EN(opts)) {
> > @@ -1068,6 +1083,7 @@ static void setup_descriptor(struct
> > f_uac1_opts *opts)
> >                 if (FUIN_EN(opts))
> >                         len += in_feature_unit_desc->bLength;
> >                 ac_header_desc->wTotalLength = cpu_to_le16(len);
> > +               iad_desc.bInterfaceCount++;
> >         }
> >         if (EPOUT_EN(opts)) {
> >                 u16 len = le16_to_cpu(ac_header_desc-
> > >wTotalLength);
> > @@ -1077,9 +1093,11 @@ static void setup_descriptor(struct
> > f_uac1_opts *opts)
> >                 if (FUOUT_EN(opts))
> >                         len += out_feature_unit_desc->bLength;
> >                 ac_header_desc->wTotalLength = cpu_to_le16(len);
> > +               iad_desc.bInterfaceCount++;
> >         }
> > 
> >         i = 0;
> > +       f_audio_desc[i++] = USBDHDR(&iad_desc);
> >         f_audio_desc[i++] = USBDHDR(&ac_interface_desc);
> >         f_audio_desc[i++] = USBDHDR(ac_header_desc);
> > 
> > @@ -1217,6 +1235,7 @@ static int f_audio_bind(struct
> > usb_configuration *c, struct usb_function *f)
> >                 }
> >         }
> > 
> > +       iad_desc.iFunction = us[STR_ASSOC].id;
> >         ac_interface_desc.iInterface = us[STR_AC_IF].id;
> >         usb_out_it_desc.iTerminal = us[STR_USB_OUT_IT].id;
> >         usb_out_it_desc.iChannelNames =
> > us[STR_USB_OUT_IT_CH_NAMES].id;
> > @@ -1302,6 +1321,8 @@ static int f_audio_bind(struct
> > usb_configuration *c, struct usb_function *f)
> >         status = usb_interface_id(c, f);
> >         if (status < 0)
> >                 goto err_free_fu;
> > +
> > +       iad_desc.bFirstInterface = status;
> >         ac_interface_desc.bInterfaceNumber = status;
> >         uac1->ac_intf = status;
> >         uac1->ac_alt = 0;
> > --
> > 2.18.0
> >