Re: [linux-usb-devel] Re: USB storage problems on OHCI..

[Ruud Linders <rkmp@xs4all.nl>]

I tried the patch but it doesn't work for me using an USB-2 Memory stick
"DiskonKey" on an USB-2 port (with uhci_hcd & ehci_hcd loaded).

After a 3 minute time-out I get
     "SCSI device sda: drive cache: write through"
and the device starts working just fine.

Unloading the ehci_hcd module doesn't make any difference.
Only when ripping out the whole mode-sense call it works immediately :-)
so it appears the device is just unhappy about the sd_do_mode_sense.

_
Regards,
	Ruud Linders

Linus Torvalds wrote:
> On 22 Sep 2003, James Bottomley wrote:
> 
>>I think we could try 4 bytes for this (even to avoid wide residue
>>problems) and see how it goes.
> 
> 
> How about just trusting the size (and as far as I can tell from the SCSI 
> specs, the size is the size _without_ the header and block descriptors), 
> and capping it at 20?
> 
> If the device reports a size that is smaller than the required one (3), we 
> just fail the request - instead of doing a small read and then making 
> decisions on data that isn't even there, like we used to do!
> 
> (The old code would use the "size" as the read length argument, which
> really looks fundamentally wrong. At the very least it should add in the
> header length etc).
> 
> Can people try this attached patch? It looks bigger than it is - in order 
> to do sane error handling for the "size is too small" case I re-organized 
> the thing a bit. The real change is just
> 
>  - capping size at 20 (real value) instead of 128 (random crud)
>  - properly add in the header and block descriptor sizes
> 
> Comments?
> 
> 			Linus
> 
> -----
> ===== drivers/scsi/sd.c 1.134 vs edited =====
> --- 1.134/drivers/scsi/sd.c	Wed Jun 25 04:47:26 2003
> +++ edited/drivers/scsi/sd.c	Mon Sep 22 12:42:32 2003
> @@ -1108,14 +1108,26 @@
>  	/* cautiously ask */
>  	res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer, 4, &data);
>  
> -	if (scsi_status_is_good(res)) {
> -		/* that went OK, now ask for the proper length */
> -		len = data.length;
> -		if (len > 128)
> -			len = 128;
> -		res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer,
> -				       len, &data);
> -	}
> +	if (!scsi_status_is_good(res))
> +		goto bad_sense;
> +
> +	/* that went OK, now ask for the proper length */
> +	len = data.length;
> +
> +	/*
> +	 * We're only interested in the first three bytes, actually.
> +	 * But the data cache page is defined for the first 20.
> +	 */
> +	if (len < 3)
> +		goto bad_sense;
> +	if (len > 20)
> +		len = 20;
> +
> +	/* Take headers and block descriptors into account */
> +	len += data.header_length + data.block_descriptor_length;
> +
> +	/* Get the data */
> +	res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer, len, &data);
>  
>  	if (scsi_status_is_good(res)) {
>  		const char *types[] = {
> @@ -1133,23 +1145,26 @@
>  
>  		printk(KERN_NOTICE "SCSI device %s: drive cache: %s\n",
>  		       diskname, types[ct]);
> +
> +		return;
> +	}
> +
> +bad_sense:
> +	if ((SRpnt->sr_sense_buffer[0] & 0x70) == 0x70
> +	     && (SRpnt->sr_sense_buffer[2] & 0x0f) == ILLEGAL_REQUEST
> +	     /* ASC 0x24 ASCQ 0x00: Invalid field in CDB */
> +	     && SRpnt->sr_sense_buffer[12] == 0x24
> +	     && SRpnt->sr_sense_buffer[13] == 0x00) {
> +		printk(KERN_NOTICE "%s: cache data unavailable\n",
> +		       diskname);
>  	} else {
> -		if ((SRpnt->sr_sense_buffer[0] & 0x70) == 0x70
> -		     && (SRpnt->sr_sense_buffer[2] & 0x0f) == ILLEGAL_REQUEST
> -		     /* ASC 0x24 ASCQ 0x00: Invalid field in CDB */
> -		     && SRpnt->sr_sense_buffer[12] == 0x24
> -		     && SRpnt->sr_sense_buffer[13] == 0x00) {
> -			printk(KERN_NOTICE "%s: cache data unavailable\n",
> -			       diskname);
> -		} else {
> -			printk(KERN_ERR "%s: asking for cache data failed\n",
> -			       diskname);
> -		}
> -		printk(KERN_ERR "%s: assuming drive cache: write through\n",
> +		printk(KERN_ERR "%s: asking for cache data failed\n",
>  		       diskname);
> -		sdkp->WCE = 0;
> -		sdkp->RCD = 0;
>  	}
> +	printk(KERN_ERR "%s: assuming drive cache: write through\n",
> +	       diskname);
> +	sdkp->WCE = 0;
> +	sdkp->RCD = 0;
>  }
>  
>  /**
> 
> 
> 
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