From 6a0bdffa0073857870a4ed1b4489762146359eb4 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 20 Jun 2012 16:04:19 -0400 Subject: SCSI & usb-storage: add try_rc_10_first flag Several bug reports have been received recently for USB mass-storage devices that don't handle READ CAPACITY(16) commands properly. They report bogus sizes, in some cases becoming unusable as a result. The bugs were triggered by commit 09b6b51b0b6c1b9bb61815baf205e4d74c89ff04 (SCSI & usb-storage: add flags for VPD pages and REPORT LUNS), which caused usb-storage to stop overriding the SCSI level reported by devices. By default, the sd driver will try READ CAPACITY(16) first for any device whose level is above SCSI_SPC_2. It seems likely that any device large enough to require the use of READ CAPACITY(16) (i.e., 2 TB or more) would be able to handle READ CAPACITY(10) commands properly. Indeed, I don't know of any devices that don't handle READ CAPACITY(10) properly. Therefore this patch (as1559) adds a new flag telling the sd driver to try READ CAPACITY(10) before READ CAPACITY(16), and sets this flag for every USB mass-storage device. If a device really is larger than 2 TB, sd will fall back to READ CAPACITY(16) just as it used to. This fixes Bugzilla #43391. Signed-off-by: Alan Stern Acked-by: Hans de Goede CC: "James E.J. Bottomley" CC: Matthew Dharm Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/usb/storage/scsiglue.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'drivers/usb/storage/scsiglue.c') diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c index a324a5d21e9..11418da9bc0 100644 --- a/drivers/usb/storage/scsiglue.c +++ b/drivers/usb/storage/scsiglue.c @@ -202,6 +202,12 @@ static int slave_configure(struct scsi_device *sdev) 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; -- cgit v1.2.3-70-g09d2