linux-kernel - Re: [PATCH 1/5] misc: rtsx_usb: Use USB remote wakeup signaling for card insertion detection

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Date:   Mon, 23 Jul 2018 10:19:42 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
cc:     arnd@...db.de, <gregkh@...uxfoundation.org>,
        <ulf.hansson@...aro.org>, <bauer.chen@...ltek.com>,
        <ricky_wu@...ltek.com>, <linux-kernel@...r.kernel.org>,
        <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 1/5] misc: rtsx_usb: Use USB remote wakeup signaling for
 card insertion detection

On Mon, 23 Jul 2018, Kai-Heng Feng wrote:

> Although rtsx_usb doesn't support card removal detection, card insertion
> will resume rtsx_usb by USB remote wakeup signaling.
> 
> When rtsx_usb gets resumed, also resumes its child devices,
> rtsx_usb_sdmmc and rtsx_usb_ms, to notify them there's a card in its
> slot.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>  drivers/misc/cardreader/rtsx_usb.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/misc/cardreader/rtsx_usb.c b/drivers/misc/cardreader/rtsx_usb.c
> index b97903ff1a72..fed83453e5c5 100644
> --- a/drivers/misc/cardreader/rtsx_usb.c
> +++ b/drivers/misc/cardreader/rtsx_usb.c
> @@ -723,8 +723,20 @@ static int rtsx_usb_suspend(struct usb_interface *intf, pm_message_t message)
>  	return 0;
>  }
>  
> +static int rtsx_usb_resume_child(struct device *dev, void *data)
> +{
> +	/* No need to wake up self again */
> +	if (dev == data)
> +		return 0;

Is this test actually needed?  device_for_each_child() won't enumerate 
the device it is called for, only that device's children.

> +
> +	dev_dbg(dev, "%s called\n", __func__);

Not necessary.  People can use ftrace if they want this information.

Alan Stern

> +	pm_request_resume(dev);
> +	return 0;
> +}
> +
>  static int rtsx_usb_resume(struct usb_interface *intf)
>  {
> +	device_for_each_child(&intf->dev, &intf->dev, rtsx_usb_resume_child);
>  	return 0;
>  }
>  
> @@ -734,6 +746,7 @@ static int rtsx_usb_reset_resume(struct usb_interface *intf)
>  		(struct rtsx_ucr *)usb_get_intfdata(intf);
>  
>  	rtsx_usb_reset_chip(ucr);
> +	device_for_each_child(&intf->dev, &intf->dev, rtsx_usb_resume_child);
>  	return 0;
>  }
>  
>