linux-kernel - Re: [PATCH 3/6] ALSA: line6: Return error if device not responding

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Date:	Wed, 11 Feb 2015 10:43:03 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Chris Rorvick <chris@...vick.com>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	Stefan Hajnoczi <stefanha@...il.com>
Subject: Re: [PATCH 3/6] ALSA: line6: Return error if device not responding

At Tue, 10 Feb 2015 23:03:14 -0600,
Chris Rorvick wrote:
> 
> Put an upper bound on how long we will wait for the device to respond to
> a read/write request (i.e., 100 milliseconds) and return an error if
> this is reached.
> 
> Signed-off-by: Chris Rorvick <chris@...vick.com>

Applied, thanks.


Takashi

> ---
>  sound/usb/line6/driver.c | 29 +++++++++++++++++++++++------
>  1 file changed, 23 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index 222c14f..2a33f3e 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -297,6 +297,7 @@ static void line6_data_received(struct urb *urb)
>  }
>  
>  #define LINE6_READ_WRITE_STATUS_DELAY 2  /* milliseconds */
> +#define LINE6_READ_WRITE_MAX_RETRIES 50
>  
>  /*
>  	Read data from device.
> @@ -307,6 +308,7 @@ int line6_read_data(struct usb_line6 *line6, u16 address, void *data,
>  	struct usb_device *usbdev = line6->usbdev;
>  	int ret;
>  	unsigned char len;
> +	unsigned count;
>  
>  	/* query the serial number: */
>  	ret = usb_control_msg(usbdev, usb_sndctrlpipe(usbdev, 0), 0x67,
> @@ -320,7 +322,7 @@ int line6_read_data(struct usb_line6 *line6, u16 address, void *data,
>  	}
>  
>  	/* Wait for data length. We'll get 0xff until length arrives. */
> -	do {
> +	for (count = 0; count < LINE6_READ_WRITE_MAX_RETRIES; count++) {
>  		mdelay(LINE6_READ_WRITE_STATUS_DELAY);
>  
>  		ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0), 0x67,
> @@ -333,9 +335,16 @@ int line6_read_data(struct usb_line6 *line6, u16 address, void *data,
>  				"receive length failed (error %d)\n", ret);
>  			return ret;
>  		}
> -	} while (len == 0xff);
>  
> -	if (len != datalen) {
> +		if (len != 0xff)
> +			break;
> +	}
> +
> +	if (len == 0xff) {
> +		dev_err(line6->ifcdev, "read failed after %d retries\n",
> +			count);
> +		return -EIO;
> +	} else if (len != datalen) {
>  		/* should be equal or something went wrong */
>  		dev_err(line6->ifcdev,
>  			"length mismatch (expected %d, got %d)\n",
> @@ -367,6 +376,7 @@ int line6_write_data(struct usb_line6 *line6, u16 address, void *data,
>  	struct usb_device *usbdev = line6->usbdev;
>  	int ret;
>  	unsigned char status;
> +	int count;
>  
>  	ret = usb_control_msg(usbdev, usb_sndctrlpipe(usbdev, 0), 0x67,
>  			      USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
> @@ -379,7 +389,7 @@ int line6_write_data(struct usb_line6 *line6, u16 address, void *data,
>  		return ret;
>  	}
>  
> -	do {
> +	for (count = 0; count < LINE6_READ_WRITE_MAX_RETRIES; count++) {
>  		mdelay(LINE6_READ_WRITE_STATUS_DELAY);
>  
>  		ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0),
> @@ -394,9 +404,16 @@ int line6_write_data(struct usb_line6 *line6, u16 address, void *data,
>  				"receiving status failed (error %d)\n", ret);
>  			return ret;
>  		}
> -	} while (status == 0xff);
>  
> -	if (status != 0) {
> +		if (status != 0xff)
> +			break;
> +	}
> +
> +	if (status == 0xff) {
> +		dev_err(line6->ifcdev, "write failed after %d retries\n",
> +			count);
> +		return -EIO;
> +	} else if (status != 0) {
>  		dev_err(line6->ifcdev, "write failed (error %d)\n", ret);
>  		return -EINVAL;
>  	}
> -- 
> 2.1.0
> 
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