Am Mittwoch, 31. Januar 2007 17:22 schrieb Alan Stern:
> On Wed, 31 Jan 2007, Oliver Neukum wrote:
> If some other device ends up needing this in the future, what makes you
> think the heuristic you have chosen will be appropriate?
I've checked my disks and asked for counterexamples.
If you have a better heuristics, please tell me. It is derived
from the informal "rules" of pseudo CHS.
> > + /* Some devices have version which report the correct sizes
> > + * and others which do not. We guess size according toa heuristic
> > + * and err on the side of lowering the capacity. */
> > + if (sdp->guess_capacity)
>
> The patch doesn't define sdp->guess_capacity anywhere.
This is the second time today. I need a notebook. Corrected version included.
> > + if (sdkp->capacity % 63 || sdkp->capacity % 255)
> > + --sdkp->capacity;
>
> This is a strange computation. You avoid decrementing the capacity iff it
> is already divisible both by 63 and by 255. Maybe you really want to use
> && rather than || ? The idea being, I presume, that the last partition
> will extend only as far as a pseudo-cylinder boundary.
Yes, but I am conservative. When in doubt, decrement.
This patch is a result of despair, I am running out of solutions.
Regards
Oliver
----
--- a/drivers/usb/storage/unusual_devs.h 2007-01-31 14:48:08.000000000
+0100
+++ b/drivers/usb/storage/unusual_devs.h 2007-01-31 15:37:40.000000000
+0100
@@ -1323,7 +1323,7 @@
"DataStor",
"USB4500 FW1.04",
US_SC_DEVICE, US_PR_DEVICE, NULL,
- US_FL_FIX_CAPACITY),
+ US_FL_CAPACITY_HEURISTICS),
/* Control/Bulk transport for all SubClass values */
USUAL_DEV(US_SC_RBC, US_PR_CB, USB_US_TYPE_STOR),
--- a/drivers/usb/storage/scsiglue.c 2007-01-31 14:56:36.000000000 +0100
+++ b/drivers/usb/storage/scsiglue.c 2007-01-31 15:37:35.000000000 +0100
@@ -155,6 +155,12 @@
if (us->flags & US_FL_FIX_CAPACITY)
sdev->fix_capacity = 1;
+ /* A few disks have two indistinguishable version, one of
+ * which reports the correct capacity and the other does not.
+ * The sd driver has to guess which is the case. */
+ if (us->flags & US_FL_CAPACITY_HEURISTICS)
+ sdev->guess_capacity = 1;
+
/* Some devices report a SCSI revision level above 2 but are
* unable to handle the REPORT LUNS command (for which
* support is mandatory at level 3). Since we already have
--- a/drivers/scsi/sd.c 2007-01-31 15:33:57.000000000 +0100
+++ b/drivers/scsi/sd.c 2007-01-31 15:37:52.000000000 +0100
@@ -1274,6 +1274,13 @@
if (sdp->fix_capacity)
--sdkp->capacity;
+ /* Some devices have version which report the correct sizes
+ * and others which do not. We guess size according toa heuristic
+ * and err on the side of lowering the capacity. */
+ if (sdp->guess_capacity)
+ if (sdkp->capacity % 63 || sdkp->capacity % 255)
+ --sdkp->capacity;
+
got_data:
if (sector_size == 0) {
sector_size = 512;
--- a/include/linux/usb_usual.h 2007-01-31 14:49:55.000000000 +0100
+++ b/include/linux/usb_usual.h 2007-01-31 15:37:49.000000000 +0100
@@ -46,7 +46,9 @@
US_FLAG(MAX_SECTORS_64, 0x00000400) \
/* Sets max_sectors to 64 */ \
US_FLAG(IGNORE_DEVICE, 0x00000800) \
- /* Don't claim device */
+ /* Don't claim device */ \
+ US_FLAG(CAPACITY_HEURISTICS, 0x00001000) \
+ /* sometimes sizes is too big */
#define US_FLAG(name, value) US_FL_##name = value ,
enum { US_DO_ALL_FLAGS };
--- a/include/scsi/scsi_device.h 2007-01-31 15:17:30.000000000 +0100
+++ b/include/scsi/scsi_device.h 2007-01-31 15:37:55.000000000 +0100
@@ -122,6 +122,7 @@
unsigned no_uld_attach:1; /* disable connecting to upper level drivers
*/
unsigned select_no_atn:1;
unsigned fix_capacity:1; /* READ_CAPACITY is too high by 1 */
+ unsigned guess_capacity:1; /* READ_CAPACITY might be too high by 1
*/
unsigned retry_hwerror:1; /* Retry HARDWARE_ERROR */
unsigned int device_blocked; /* Device returned QUEUE_FULL. */
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