Re: [PATCH v3] Re: another unusual flag for a really limited device
Alan Stern <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Wed, 28 Nov 2007, Doug Maxey wrote:
> + /* And at least one more device needs an even smaller max.
> + * When testing the native PAGE_SIZE, clamp at 8k. No need
> + * allow a 64K or even 16M page in there.
> + */
Why not combine the code for the two flags, as shown in the partial
patch below?
Also, trying to clamp at 8 KB is futile. Read the source code for
blk_queue_max_sectors() in drivers/block/ll_rw_blk.c and you'll see.
Alan Stern
Index: usb-2.6/drivers/usb/storage/scsiglue.c
===================================================================
--- usb-2.6.orig/drivers/usb/storage/scsiglue.c
+++ usb-2.6/drivers/usb/storage/scsiglue.c
@@ -113,10 +113,19 @@ static int slave_configure(struct scsi_d
/* Many devices have trouble transfering more than 32KB at a time,
* while others have trouble with more than 64K. At this time we
* are limiting both to 32K (64 sectores).
+ *
+ * Some other devices have trouble transferring even that much.
+ * We'll limit them to PAGE_CACHE_SIZE, which is the minimum.
*/
- if ((us->flags & US_FL_MAX_SECTORS_64) &&
- sdev->request_queue->max_sectors > 64)
- blk_queue_max_sectors(sdev->request_queue, 64);
+ if (us->flags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN)) {
+ unsigned int max_sectors = 64;
+
+ if (us->flags & US_FL_MAX_SECTORS_MIN)
+ max_sectors = PAGE_CACHE_SIZE >> 9;
+ if (sdev->request_queue->max_sectors > max_sectors)
+ blk_queue_max_sectors(sdev->request_queue,
+ max_sectors);
+ }
/* We can't put these settings in slave_alloc() because that gets
* called before the device type is known. Consequently these
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