Re: READ_CAPACITY_16 vs. READ_CAPACITY_10

[Hannes Reinecke <hare@suse.de>]

On 09/10/2013 03:56 PM, Oliver Neukum wrote:
> Hi Hannes,
> 
> you objected to this patch saying there's a possibilty that
> HS devices may also need this feature, which would require
> a quirk. Does this mean that the patch is acceptable only
> with an additional predefined quirk, or do you insist that all
> devices be handled with quirks?
> 
> 	Regards
> 		Oliver
> 
> +++ b/drivers/usb/storage/scsiglue.c
> @@ -211,8 +211,11 @@ static int slave_configure(struct
> scsi_device0*sdev)
>  		/*
>  		 * Many devices do not respond properly to READ_CAPACITY_16.
>  		 * Tell the SCSI layer to try READ_CAPACITY_10 first.
> +		 * However some USB 3.0 drive enclosures return capacity
> +		 * modulo 2TB
>  		 */
> -		sdev->try_rc_10_first = 1;
> +		if (us->pusb_dev->speed < USB_SPEED_SUPER)
> +			sdev->try_rc_10_first = 1;
>  
>  		/* assume SPC3 or latter devices support sense size > 18 */
>  		if (sdev->scsi_level > SCSI_SPC_2)
> 
Predefined quirks is okay.
My main objection here is that the original issue most likely is a
buggy firmware, so there is a _very_ good chance that it'll be
resolved in firmware in the near future.
At the same time, other firmwares might continue to not support
READ_CAPACITY_16 while enabling HS.
So both issues really should be kept separate, which'll warrant a
new flag.
Which of course could be set to on per default on HS devices.
As long as we can switch is off again ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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