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Date: Sat, 2 Jul 2022 16:41:32 +0800
From: Chunfeng Yun <chunfeng.yun@...iatek.com>
To: Ruslan Bilovol <ruslan.bilovol@...il.com>
CC: Felipe Balbi <balbi@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Pavel Hofman <pavel.hofman@...tera.com>,
Julian Scheel <julian@...st.de>,
Yunhao Tian <t123yh.xyz@...il.com>,
xin lin <xin.lin@...iatek.com>,
"Linux USB" <linux-usb@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
<linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v2] usb: gadget: f_uac1: add interface association
descriptor
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@...iatek.com> wrote:
> >
> > From: xin lin <xin.lin@...iatek.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@...iatek.com>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.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
> >
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