Re: [PATCH v26 21/33] ASoC: qcom: qdsp6: Add USB backend ASoC driver for Q6

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 8/29/24 21:40, Wesley Cheng wrote:
> Create a USB BE component that will register a new USB port to the ASoC USB
> framework.  This will handle determination on if the requested audio
> profile is supported by the USB device currently selected.
> 
> Check for if the PCM format is supported during the hw_params callback.  If
> the profile is not supported then the userspace ALSA entity will receive an
> error, and can take further action.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>  include/sound/q6usboffload.h  |  20 +++
>  sound/soc/qcom/Kconfig        |  10 ++
>  sound/soc/qcom/qdsp6/Makefile |   1 +
>  sound/soc/qcom/qdsp6/q6usb.c  | 246 ++++++++++++++++++++++++++++++++++
>  4 files changed, 277 insertions(+)
>  create mode 100644 include/sound/q6usboffload.h
>  create mode 100644 sound/soc/qcom/qdsp6/q6usb.c
> 
> diff --git a/include/sound/q6usboffload.h b/include/sound/q6usboffload.h
> new file mode 100644
> index 000000000000..49ab2c34b84c
> --- /dev/null
> +++ b/include/sound/q6usboffload.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0
> + *
> + * linux/sound/q6usboffload.h -- QDSP6 USB offload

not sure about the linux/ prefix?

> + *
> + * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +/**
> + * struct q6usb_offload
> + * @dev - dev handle to usb be
> + * @sid - streamID for iommu
> + * @intr_num - usb interrupter number
> + * @domain - allocated iommu domain
> + **/
> +struct q6usb_offload {
> +	struct device *dev;
> +	long long sid;
> +	u16 intr_num;
> +	struct iommu_domain *domain;
> +};

consider reordering to avoid holes/alignment issues, e.g. all pointers
first, then long long then u16


> +static int q6usb_hw_params(struct snd_pcm_substream *substream,
> +			   struct snd_pcm_hw_params *params,
> +			   struct snd_soc_dai *dai)
> +{
> +	struct q6usb_port_data *data = dev_get_drvdata(dai->dev);
> +	struct snd_soc_pcm_runtime *rtd = substream->private_data;
> +	struct snd_soc_dai *cpu_dai = snd_soc_rtd_to_cpu(rtd, 0);
> +	int direction = substream->stream;
> +	struct q6afe_port *q6usb_afe;
> +	struct snd_soc_usb_device *sdev;
> +	int ret = -EINVAL;
> +
> +	mutex_lock(&data->mutex);
> +
> +	/* No active chip index */
> +	if (list_empty(&data->devices))
> +		goto out;

-ENODEV for the default return value>?

> +
> +	sdev = list_last_entry(&data->devices, struct snd_soc_usb_device, list);
> +
> +	ret = snd_soc_usb_find_supported_format(sdev->chip_idx, params, direction);
> +	if (ret < 0)
> +		goto out;
> +
> +	q6usb_afe = q6afe_port_get_from_id(cpu_dai->dev, USB_RX);
> +	if (IS_ERR(q6usb_afe))
> +		goto out;
> +
> +	/* Notify audio DSP about the devices being offloaded */
> +	ret = afe_port_send_usb_dev_param(q6usb_afe, sdev->card_idx,
> +					  sdev->ppcm_idx[sdev->num_playback - 1]);

don't you need a symmetrical notification upon hw_free()?

Also what happens if there are multiple calls to hw_params, which is
quite legit in ALSA/ASoC?