[PATCH v2] Re: another unusual flag for a really limited device

On Thu, 15 Nov 2007 13:09:41 EST, Alan Stern wrote:
> On Thu, 15 Nov 2007, Matthew Dharm wrote:
> 
> > > I wish we could.  Our file handles values in units of sectors (512 
> > > bytes) and the other sysfs entry handles values in units of KB.  It's 
> > > even named "max_sectors_kb".
> > 
> > I'm guessing that it's worse than that... I'll bet that we handle a number
> > of sectors, regardless of sector size.  So a sector might not be 512 bytes.
> 
> No, things aren't _that_ bad!  The block layer documentation states the
> value is in terms of "logical" sectors that are always 512 bytes, not
> "hardware" sectors that are whatever the device wants them to be.
> 

And on that note, and incorporating the requested changes, here is a 
new patch.

>From ff01889fac202ffb657a06e74ecd406c4229394d Mon Sep 17 00:00:00 2001
From: Doug Maxey <[email protected]>
Date: Tue, 27 Nov 2007 18:42:42 -0600
Subject: [PATCH 1/1] usb-storage: limit devices that cannot handle 32k transfers

When a device cannot handle the smallest previously limited transfer
size (64 blocks) without stalling, limit the device to the amount of
packets that fit in a platform native page.

Cc: Mathew Dharm <[email protected]>
Cc: Alan Stern <[email protected]>
Cc: Pete Zaitcev <[email protected]>
Signed-off-by: Doug Maxey <[email protected]>
---
 drivers/usb/storage/scsiglue.c     |   11 +++++++++++
 drivers/usb/storage/unusual_devs.h |    7 +++++++
 include/linux/usb_usual.h          |    5 ++++-
 3 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 1ba19ea..c071bca 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -118,6 +118,17 @@ static int slave_configure(struct scsi_device *sdev)
 			sdev->request_queue->max_sectors > 64)
 		blk_queue_max_sectors(sdev->request_queue, 64);
 
+	/* 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.
+	 */
+	if (us->flags & US_FL_MAX_SECTORS_MIN) {
+		int min = min(PAGE_SIZE, 8192) / 512;
+
+		if (sdev->request_queue->max_sectors > min)
+			blk_queue_max_sectors(sdev->request_queue, min);
+	}
+
 	/* We can't put these settings in slave_alloc() because that gets
 	 * called before the device type is known.  Consequently these
 	 * settings can't be overridden via the scsi devinfo mechanism. */
diff --git a/drivers/usb/storage/unusual_devs.h b/drivers/usb/storage/unusual_devs.h
index 22ab238..f464b18 100644
--- a/drivers/usb/storage/unusual_devs.h
+++ b/drivers/usb/storage/unusual_devs.h
@@ -376,6 +376,13 @@ UNUSUAL_DEV(  0x04b0, 0x0417, 0x0100, 0x0100,
 		US_SC_DEVICE, US_PR_DEVICE, NULL,
 		US_FL_FIX_CAPACITY),
 
+/* Reported by Doug Maxey ([email protected]) */
+UNUSUAL_DEV(  0x04b3, 0x4001, 0x0110, 0x0110,
+		"IBM",
+		"IBM RSA2",
+		US_SC_DEVICE, US_PR_CB, NULL,
+		US_FL_MAX_SECTORS_MIN),
+
 /* BENQ DC5330
  * Reported by Manuel Fombuena <[email protected]> and
  * Frank Copeland <[email protected]> */
diff --git a/include/linux/usb_usual.h b/include/linux/usb_usual.h
index 1b792b9..5e182e5 100644
--- a/include/linux/usb_usual.h
+++ b/include/linux/usb_usual.h
@@ -48,7 +48,10 @@
 	US_FLAG(IGNORE_DEVICE,	0x00000800)			\
 		/* Don't claim device */			\
 	US_FLAG(CAPACITY_HEURISTICS,	0x00001000)		\
-		/* sometimes sizes is too big */
+		/* sometimes sizes is too big */		\
+	US_FLAG(MAX_SECTORS_MIN,0x00001000)			\
+		/* Sets max_sectors to arch min */
+
 
 #define US_FLAG(name, value)	US_FL_##name = value ,
 enum { US_DO_ALL_FLAGS };
-- 
1.5.3.6




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