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From: Alan Stern <stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>
Newsgroups: gmane.linux.usb.general
Subject: Re: USB mass-storage devices and READ CAPACITY(16)
Date: Sun, 17 Jun 2012 11:26:31 -0400 (EDT)
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Cc: Torsten Wohlfarth <towo-BOgDY73gMKaEi8DpZVb4nw@public.gmane.org>,
Sturm Flut <sturmflut-Q2DnxKCD/W3WAjrKYNhlQQ@public.gmane.org>,
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To: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
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Xref: news.gmane.org gmane.linux.usb.general:65976
Archived-At: <http://permalink.gmane.org/gmane.linux.usb.general/65976>
On Fri, 15 Jun 2012, Alan Stern wrote:
> On Fri, 15 Jun 2012, Hans de Goede wrote:
>
> > Hi,
> >
> > On 06/15/2012 08:20 PM, Alan Stern wrote:
> > > As we can see from recent bug reports, a lot of USB mass-storage
> > > devices cannot handle READ CAPACITY(16) commands properly. They send
> > > back garbage and are unusable as a result.
> > >
> > > Should we go ahead and set a flag on all these devices, telling the sd
> > > driver to try READ CAPACITY(10) first? That's a lot easier than adding
> > > more and more entries to unusual_devs.h.
> >
> > That certainly sound reasonable to me. Note that the 071b:3203 really
> > needs the US_FL_NO_READ_CAPACITY_16 flag though, as it wrongly reports
> > a capacity of -1 when there is no sd card in its slot, and in response
> > to that the kernel tries READ CAPACITY(16) and things go downhill
> > from there...
>
> Yes, we need to be able to have both flags set for the same device.
> For that card reader they would mean try READ CAPACITY(10) first, and
> if it fails, don't try READ CAPACITY(16).
In other words, I'm suggesting we adopt this patch and get rid Hans's
new unusual_devs entry.
Alan Stern
Index: usb-3.4/include/scsi/scsi_device.h
===================================================================
--- usb-3.4.orig/include/scsi/scsi_device.h
+++ usb-3.4/include/scsi/scsi_device.h
@@ -151,6 +151,7 @@ struct scsi_device {
SD_LAST_BUGGY_SECTORS */
unsigned no_read_disc_info:1; /* Avoid READ_DISC_INFO cmds */
unsigned no_read_capacity_16:1; /* Avoid READ_CAPACITY_16 cmds */
+ unsigned try_rc_10_first:1; /* Try READ_CAPACACITY_10 first */
unsigned is_visible:1; /* is the device visible in sysfs */
DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */
Index: usb-3.4/drivers/scsi/sd.c
===================================================================
--- usb-3.4.orig/drivers/scsi/sd.c
+++ usb-3.4/drivers/scsi/sd.c
@@ -1899,6 +1899,8 @@ static int sd_try_rc16_first(struct scsi
{
if (sdp->host->max_cmd_len < 16)
return 0;
+ if (sdp->try_rc_10_first)
+ return 0;
if (sdp->scsi_level > SCSI_SPC_2)
return 1;
if (scsi_device_protection(sdp))
Index: usb-3.4/drivers/usb/storage/scsiglue.c
===================================================================
--- usb-3.4.orig/drivers/usb/storage/scsiglue.c
+++ usb-3.4/drivers/usb/storage/scsiglue.c
@@ -202,6 +202,12 @@ static int slave_configure(struct scsi_d
if (us->fflags & US_FL_NO_READ_CAPACITY_16)
sdev->no_read_capacity_16 = 1;
+ /*
+ * Many devices do not respond properly to READ_CAPACITY_16.
+ * Tell the SCSI layer to try READ_CAPACITY_10 first.
+ */
+ sdev->try_rc_10_first = 1;
+
/* assume SPC3 or latter devices support sense size > 18 */
if (sdev->scsi_level > SCSI_SPC_2)
us->fflags |= US_FL_SANE_SENSE;
--
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