Adding USB device quirk - packet format?

[Olivia Mackintosh]

Hello,

I am trying to add a device quirk for the Pioneer DJM-750 mixer. I have
attached a patch to illustrate what I'm trying to achieve. It is nearly
identical to https://patchwork.kernel.org/patch/11521019/ except for the
differences in channels. I have verified the settings against valid USB
transfers.

While observing behaviour with a Windows 10 VM, the 8 pieces of data
appear to be 8 isochronous packets within a single frame as opposed to 8
microframes (each with their own transfer). Should this have any impact
on the ability for the device to function? If so, is there a setting I
am missing to account for this? Or, am I simply clutching at straws and
completely on the wrong path.

This is rather device specific so I would not expect anyone to help
troubleshoot this specific device but what I suspect is the problem is
the way the audio data is arranged in the transfer.

Any suggestions and pointers on how to proceed are very much
appreciated.

Kind regards,
Olivia Mackintosh
-------------- next part --------------
diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index 0bf370d89556..35323d010415 100644
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -3570,7 +3570,6 @@ AU0828_DEVICE(0x2040, 0x7270, "Hauppauge", "HVR-950Q"),
 		}
 	}
 },
-
 #define ALC1220_VB_DESKTOP(vend, prod) { \
 	USB_DEVICE(vend, prod),	\
 	.driver_info = (unsigned long) & (const struct snd_usb_audio_quirk) { \
@@ -3610,5 +3609,64 @@ ALC1220_VB_DESKTOP(0x26ce, 0x0a01), /* Asrock TRX40 Creator */
 		.ifnum = QUIRK_NO_INTERFACE
 	}
 },
+{
+	/*
+	 * Pioneer DJ DJM-750
+	 * 8 channels playback & 8 channels capture @ 44.1/48/96kHz S24LE
+	 */
+	USB_DEVICE_VENDOR_SPEC(0x08e4, 0x017f),
+	.driver_info = (unsigned long) &(const struct snd_usb_audio_quirk) {
+		.ifnum = QUIRK_ANY_INTERFACE,
+		.type = QUIRK_COMPOSITE,
+		.data = (const struct snd_usb_audio_quirk[]) {
+			{
+				.ifnum = 0,
+				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
+				.data = &(const struct audioformat) {
+					.formats = SNDRV_PCM_FMTBIT_S24_3LE,
+					.channels = 8,
+					.iface = 0,
+					.altsetting = 1,
+					.altset_idx = 1,
+					.endpoint = 0x05,
+					.ep_attr = USB_ENDPOINT_XFER_ISOC|
+					    USB_ENDPOINT_SYNC_ASYNC,
+					.rates = SNDRV_PCM_RATE_44100|
+						SNDRV_PCM_RATE_48000|
+						SNDRV_PCM_RATE_96000,
+					.rate_min = 44100,
+					.rate_max = 96000,
+					.nr_rates = 3,
+					.rate_table = (unsigned int[]) { 44100, 48000, 96000 }
+				}
+			},
+			{
+				.ifnum = 0,
+				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
+				.data = &(const struct audioformat) {
+					.formats = SNDRV_PCM_FMTBIT_S24_3LE,
+					.channels = 8,
+					.iface = 0,
+					.altsetting = 1,
+					.altset_idx = 1,
+					.endpoint = 0x86,
+					.ep_attr = USB_ENDPOINT_XFER_ISOC|
+						USB_ENDPOINT_SYNC_ASYNC|
+						USB_ENDPOINT_USAGE_IMPLICIT_FB,
+					.rates = SNDRV_PCM_RATE_44100|
+						SNDRV_PCM_RATE_48000|
+						SNDRV_PCM_RATE_96000,
+					.rate_min = 44100,
+					.rate_max = 96000,
+					.nr_rates = 3,
+					.rate_table = (unsigned int[]) { 44100, 48000, 96000 }
+				}
+			},
+			{
+				.ifnum = -1
+			}
+		}
+	}
+},
 
 #undef USB_DEVICE_VENDOR_SPEC
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index d7d900ebcf37..5017ff9d5bcd 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -1458,6 +1458,28 @@ static void set_format_emu_quirk(struct snd_usb_substream *subs,
 	subs->pkt_offset_adj = (emu_samplerate_id >= EMU_QUIRK_SR_176400HZ) ? 4 : 0;
 }
 
+/*
+ * Pioneer DJ DJM-750
+ * Device needs to know the sample rate when substream is started
+ */
+static int pioneer_djm_set_format_quirk(struct snd_usb_substream *subs)
+{
+	/* Convert sample rate to little endian */
+	u8 sr[3];
+
+	sr[0] = subs->cur_rate&0xff;
+	sr[1] = (subs->cur_rate>>8)&0xff;
+	sr[2] = (subs->cur_rate>>16)&0xff;
+
+	/* Configure device */
+	usb_set_interface(subs->dev, 0, 1);
+	snd_usb_ctl_msg(subs->stream->chip->dev,
+		usb_rcvctrlpipe(subs->stream->chip->dev, 0),
+		0x01, 0x22, 0x0100, 0x0086, &sr, 0x0003);
+
+	return 0;
+}
+
 void snd_usb_set_format_quirk(struct snd_usb_substream *subs,
 			      struct audioformat *fmt)
 {
@@ -1468,6 +1490,9 @@ void snd_usb_set_format_quirk(struct snd_usb_substream *subs,
 	case USB_ID(0x041e, 0x3f19): /* E-Mu 0204 USB */
 		set_format_emu_quirk(subs, fmt);
 		break;
+	case USB_ID(0x08e4, 0x017f): /* Pioneer DJM-750 */
+		pioneer_djm_set_format_quirk(subs);
+		break;
 	}
 }