Hi Pierre,
On 8/30/2024 3:05 AM, Pierre-Louis Bossart wrote:
On 8/29/24 21:41, Wesley Cheng wrote:
In order to allow userspace/applications know about USB offloading status, expose a sound kcontrol that fetches information about which sound card and PCM index the USB device is mapped to for supporting offloading. In the USB audio offloading framework, the ASoC BE DAI link is the entity responsible for registering to the SOC USB layer.
It is expected for the USB SND offloading driver to add the kcontrol to the sound card associated with the USB audio device. An example output would look like:
this is very odd, the offloading driver adds a control to another card?
That seems like a rather important layering violation.
I thought it was done the other way, the USB audio card created a control that would point to the other card/device.
The USB SND offloading vendor driver (qc_audio_offload), which technically co-exists with USB SND core, is the entity that will add the offload kcontrol to the USB audio device's sound card. Initially, I had the kcontrol creation as part of the USB SND mixer, but I believe Takashi preferred if the vendor driver did it instead.
tinymix -D 1 get 'USB Offload Playback Route PCM#0' -1, -1 (range -1->255)
This example signifies that there is no mapped ASoC path available for the USB SND device.
but that control would not even exist if the ASoC-based driver isn't probed.
It's become really hard to follow, I've been on all this for 1.5hrs and losing track of the design.
Hence why it probably is a good idea to leave it within the USB offload vendor driver. There are checks to ensure that the ASoC based driver is probed/available before the kcontrols are created for a device. If there are devices that were identified before the ASoC components were probed, then the snd_usb_rediscover_devices() is triggered as part of soc-usb, and that would call the connect_cb() callback to the USB SND vendor offload driver to create the kcontrol.
Thanks
Wesley Cheng
tinymix -D 1 get 'USB Offload Playback Route PCM#0' 0, 0 (range -1->255)
This example signifies that the offload path is available over ASoC sound card index#0 and PCM device#0.
Signed-off-by: Wesley Cheng quic_wcheng@quicinc.com
sound/usb/Kconfig | 10 +++ sound/usb/Makefile | 2 + sound/usb/mixer_usb_offload.c | 102 ++++++++++++++++++++++++++++++ sound/usb/mixer_usb_offload.h | 17 +++++ sound/usb/qcom/Makefile | 2 +- sound/usb/qcom/qc_audio_offload.c | 2 + 6 files changed, 134 insertions(+), 1 deletion(-) create mode 100644 sound/usb/mixer_usb_offload.c create mode 100644 sound/usb/mixer_usb_offload.h
diff --git a/sound/usb/Kconfig b/sound/usb/Kconfig index 5cc3eaf53e6b..e3fbf9541d0b 100644 --- a/sound/usb/Kconfig +++ b/sound/usb/Kconfig @@ -176,10 +176,20 @@ config SND_BCD2000 To compile this driver as a module, choose M here: the module will be called snd-bcd2000.
+config SND_USB_OFFLOAD_MIXER
- tristate "USB Audio Offload mixer control"
- help
Say Y to enable the USB audio offloading mixer controls. Thisexposes an USB offload capable kcontrol to signal to applicationsabout which platform sound card can support USB audio offload.The returning values specify the mapped ASoC card and PCM devicethe USB audio device is associated to.config SND_USB_AUDIO_QMI tristate "Qualcomm Audio Offload driver" depends on QCOM_QMI_HELPERS && SND_USB_AUDIO && USB_XHCI_SIDEBAND && SND_SOC_USB select SND_PCM
- select SND_USB_OFFLOAD_MIXER help Say Y here to enable the Qualcomm USB audio offloading feature.
diff --git a/sound/usb/Makefile b/sound/usb/Makefile index 54a06a2f73ca..2f19f854944c 100644 --- a/sound/usb/Makefile +++ b/sound/usb/Makefile @@ -36,3 +36,5 @@ obj-$(CONFIG_SND_USB_US122L) += snd-usbmidi-lib.o
obj-$(CONFIG_SND) += misc/ usx2y/ caiaq/ 6fire/ hiface/ bcd2000/ qcom/ obj-$(CONFIG_SND_USB_LINE6) += line6/
+obj-$(CONFIG_SND_USB_OFFLOAD_MIXER) += mixer_usb_offload.o diff --git a/sound/usb/mixer_usb_offload.c b/sound/usb/mixer_usb_offload.c new file mode 100644 index 000000000000..16e2fd634684 --- /dev/null +++ b/sound/usb/mixer_usb_offload.c @@ -0,0 +1,102 @@ +// SPDX-License-Identifier: GPL-2.0 +/*
- Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
- */
+#include <linux/usb.h>
+#include <sound/core.h> +#include <sound/control.h> +#include <sound/soc-usb.h>
+#include "usbaudio.h" +#include "card.h" +#include "helper.h" +#include "mixer.h"
+#include "mixer_usb_offload.h"
+#define PCM_IDX(n) ((n) & 0xffff) +#define CARD_IDX(n) ((n) >> 16)
+static int +snd_usb_offload_route_get(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_value *ucontrol)+{
- struct device *sysdev = snd_kcontrol_chip(kcontrol);
- int ret;
- ret = snd_soc_usb_update_offload_route(sysdev,
CARD_IDX(kcontrol->private_value),PCM_IDX(kcontrol->private_value),SNDRV_PCM_STREAM_PLAYBACK,ucontrol->value.integer.value);- if (ret < 0) {
ucontrol->value.integer.value[0] = -1;ucontrol->value.integer.value[1] = -1;- }
- return 0;
+}
+static int snd_usb_offload_route_info(struct snd_kcontrol *kcontrol,
struct snd_ctl_elem_info *uinfo)+{
- uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
- uinfo->count = 2;
- uinfo->value.integer.min = -1;
- /* Arbitrary max value, as there is no 'limit' on number of PCM devices */
- uinfo->value.integer.max = 0xff;
- return 0;
+}
+static struct snd_kcontrol_new snd_usb_offload_mapped_ctl = {
- .iface = SNDRV_CTL_ELEM_IFACE_CARD,
- .access = SNDRV_CTL_ELEM_ACCESS_READ,
- .info = snd_usb_offload_route_info,
- .get = snd_usb_offload_route_get,
+};
+/**
- snd_usb_offload_create_ctl() - Add USB offload bounded mixer
- @chip - USB SND chip device
- Creates a sound control for a USB audio device, so that applications can
- query for if there is an available USB audio offload path, and which
- card is managing it.
- */
+int snd_usb_offload_create_ctl(struct snd_usb_audio *chip) +{
- struct usb_device *udev = chip->dev;
- struct snd_kcontrol_new *chip_kctl;
- struct snd_usb_substream *subs;
- struct snd_usb_stream *as;
- char ctl_name[37];
- int ret;
- list_for_each_entry(as, &chip->pcm_list, list) {
subs = &as->substream[SNDRV_PCM_STREAM_PLAYBACK];if (!subs->ep_num)continue;chip_kctl = &snd_usb_offload_mapped_ctl;chip_kctl->count = 1;/** Store the associated USB SND card number and PCM index for* the kctl.*/chip_kctl->private_value = as->pcm_index |chip->card->number << 16;sprintf(ctl_name, "USB Offload Playback Route PCM#%d",as->pcm_index);chip_kctl->name = ctl_name;ret = snd_ctl_add(chip->card, snd_ctl_new1(chip_kctl,udev->bus->sysdev));if (ret < 0)break;- }
- return ret;
+} +EXPORT_SYMBOL_GPL(snd_usb_offload_create_ctl); diff --git a/sound/usb/mixer_usb_offload.h b/sound/usb/mixer_usb_offload.h new file mode 100644 index 000000000000..3f6e2a8b19c8 --- /dev/null +++ b/sound/usb/mixer_usb_offload.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0
- Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
- */
+#ifndef __USB_OFFLOAD_MIXER_H +#define __USB_OFFLOAD_MIXER_H
+#if IS_ENABLED(CONFIG_SND_USB_OFFLOAD_MIXER) +int snd_usb_offload_create_ctl(struct snd_usb_audio *chip); +#else +static inline int snd_usb_offload_create_ctl(struct snd_usb_audio *chip) +{
- return 0;
+} +#endif +#endif /* __USB_OFFLOAD_MIXER_H */ diff --git a/sound/usb/qcom/Makefile b/sound/usb/qcom/Makefile index a81c9b28d484..4005e8391ab9 100644 --- a/sound/usb/qcom/Makefile +++ b/sound/usb/qcom/Makefile @@ -1,2 +1,2 @@ snd-usb-audio-qmi-objs := usb_audio_qmi_v01.o qc_audio_offload.o -obj-$(CONFIG_SND_USB_AUDIO_QMI) += snd-usb-audio-qmi.o \ No newline at end of file +obj-$(CONFIG_SND_USB_AUDIO_QMI) += snd-usb-audio-qmi.o diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c index a7ad15404fd1..5b9262a116be 100644 --- a/sound/usb/qcom/qc_audio_offload.c +++ b/sound/usb/qcom/qc_audio_offload.c @@ -36,6 +36,7 @@ #include "../helper.h" #include "../pcm.h" #include "../power.h" +#include "../mixer_usb_offload.h"
#include "usb_audio_qmi_v01.h"
@@ -1703,6 +1704,7 @@ static void qc_usb_audio_offload_probe(struct snd_usb_audio *chip) sdev->card_idx = chip->card->number; sdev->chip_idx = chip->index;
snd_usb_offload_create_ctl(chip);