linux-kernel - Re: [RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform op callbacks

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Message-ID: <CANqn-rhAWKVrSGKkoDCC+Jy6qdceSqo22KYb-5k+haHpcgQJaA@mail.gmail.com>
Date:   Tue, 21 Feb 2023 01:11:04 +0800
From:   Albert Wang <albertccwang@...gle.com>
To:     Wesley Cheng <quic_wcheng@...cinc.com>
Cc:     srinivas.kandagatla@...aro.org, mathias.nyman@...el.com,
        perex@...ex.cz, lgirdwood@...il.com, andersson@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, gregkh@...uxfoundation.org,
        Thinh.Nguyen@...opsys.com, broonie@...nel.org,
        bgoswami@...cinc.com, tiwai@...e.com, robh+dt@...nel.org,
        agross@...nel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
        quic_jackp@...cinc.com, quic_plai@...cinc.com
Subject: Re: [RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform
 op callbacks

Hi Wesley,

It looks like your audio offload driver will fetch the required
resources for a stream enable request. But we have different designs.
In the integration with your patch set, we found we still need a call
back function in card.c when the usb set interface is done, in which
we would call the new API, xhci_get_xfer_resource(), to get the EP
transfer ring address. Of course, we will try the
platform_ops->connect_cb() first to see if it is able to cover what we
need or not.


Thanks,
Albert Wang

Albert Wang | Pixel USB Software  | albertccwang@...gle.com | +886-918-695-245


On Thu, Jan 26, 2023 at 11:16 AM Wesley Cheng <quic_wcheng@...cinc.com> wrote:
>
> Allow for different platforms to be notified on USB SND connect/disconnect
> seqeunces.  This allows for platform USB SND modules to properly initialize
> and populate internal structures with references to the USB SND chip
> device.
>
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> ---
>  sound/usb/card.c | 28 ++++++++++++++++++++++++++++
>  sound/usb/card.h | 20 ++++++++++++++++++++
>  2 files changed, 48 insertions(+)
>
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 26268ffb8274..803230343c16 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -117,6 +117,24 @@ MODULE_PARM_DESC(skip_validation, "Skip unit descriptor validation (default: no)
>  static DEFINE_MUTEX(register_mutex);
>  static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
>  static struct usb_driver usb_audio_driver;
> +static struct snd_usb_platform_ops *platform_ops;
> +
> +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
> +{
> +       if (platform_ops)
> +               return -EEXIST;
> +
> +       platform_ops = ops;
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_usb_register_platform_ops);
> +
> +int snd_usb_unregister_platform_ops(void)
> +{
> +       platform_ops = NULL;
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);
>
>  /*
>   * disconnect streams
> @@ -910,6 +928,10 @@ static int usb_audio_probe(struct usb_interface *intf,
>         usb_set_intfdata(intf, chip);
>         atomic_dec(&chip->active);
>         mutex_unlock(&register_mutex);
> +
> +       if (platform_ops->connect_cb)
> +               platform_ops->connect_cb(intf, chip);
> +
>         return 0;
>
>   __error:
> @@ -943,6 +965,9 @@ static void usb_audio_disconnect(struct usb_interface *intf)
>         if (chip == USB_AUDIO_IFACE_UNUSED)
>                 return;
>
> +       if (platform_ops->disconnect_cb)
> +               platform_ops->disconnect_cb(intf);
> +
>         card = chip->card;
>
>         mutex_lock(&register_mutex);
> @@ -1087,6 +1112,9 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
>                 chip->system_suspend = chip->num_suspended_intf;
>         }
>
> +       if (platform_ops->suspend_cb)
> +               platform_ops->suspend_cb(intf, message);
> +
>         return 0;
>  }
>
> diff --git a/sound/usb/card.h b/sound/usb/card.h
> index 40061550105a..2249c411c3a1 100644
> --- a/sound/usb/card.h
> +++ b/sound/usb/card.h
> @@ -206,4 +206,24 @@ struct snd_usb_stream {
>         struct list_head list;
>  };
>
> +struct snd_usb_platform_ops {
> +       void (*connect_cb)(struct usb_interface *intf, struct snd_usb_audio *chip);
> +       void (*disconnect_cb)(struct usb_interface *intf);
> +       void (*suspend_cb)(struct usb_interface *intf, pm_message_t message);
> +};
> +
> +#if IS_ENABLED(CONFIG_SND_USB_AUDIO)
> +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);
> +int snd_usb_unregister_platform_ops(void);
> +#else
> +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops)
> +{
> +       return -EOPNOTSUPP;
> +}
> +
> +int snd_usb_unregister_platform_ops(void)
> +{
> +       return -EOPNOTSUPP;
> +}
> +#endif /* IS_ENABLED(CONFIG_SND_USB_AUDIO) */
>  #endif /* __USBAUDIO_CARD_H */