Re: [PATCH] USB-Core, fix cardreader not found during init

On Mon, 13 Aug 2007, Steffen Koepf wrote:

> From: Steffen Koepf <[email protected]>
> 
> There is a USB-Device Init-Problem with the Apacer AE161 USB-Cardreader,
> which contains the Chip AU6375. The Cardreader init fails in about 50%
> of system boots, with the following lines:
> 
> usb 1-6: unable to read config index 0 descriptor/all
> usb 1-6: can't read configurations, error -71
> hub 1-0:1.0: Cannot enable port 6.  Maybe the USB cable is bad?
> 
> The patch let's the kernel stay in the loop if a usb_control_msg() fails, 
> the cardreader is detected properly and the loop is never executed more
> than two times. The second call of usb_control_msg succeeds always. Maybe 
> it was the developer's goal of the loop to fix such things?
> Kernel: 2.6.22.2
> 
> Signed-off-by: Steffen Koepf <[email protected]>
> 
> ---
> --- linux-2.6.22.2/drivers/usb/core/message.c.orig	Mon Aug 13 22:12:34 2007
> +++ linux-2.6.22.2/drivers/usb/core/message.c	Mon Aug 13 22:12:52 2007
> @@ -634,6 +634,8 @@ int usb_get_descriptor(struct usb_device
>  			result = -EPROTO;
>  			continue;
>  		}
> +		if (result < 0)
> +			continue;
>  		break;
>  	}
>  	return result;

This patch is the wrong way to do it.  You should try this patch 
instead.

Alan Stern


Index: 2.6.22/drivers/usb/core/message.c
===================================================================
--- 2.6.22.orig/drivers/usb/core/message.c
+++ 2.6.22/drivers/usb/core/message.c
@@ -623,12 +623,12 @@ int usb_get_descriptor(struct usb_device
 	memset(buf,0,size);	// Make sure we parse really received data
 
 	for (i = 0; i < 3; ++i) {
-		/* retry on length 0 or stall; some devices are flakey */
+		/* retry on length 0 or error; some devices are flakey */
 		result = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
 				USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
 				(type << 8) + index, 0, buf, size,
 				USB_CTRL_GET_TIMEOUT);
-		if (result == 0 || result == -EPIPE)
+		if (result <= 0)
 			continue;
 		if (result > 1 && ((u8 *)buf)[1] != type) {
 			result = -EPROTO;


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