[PATCH v4] Re: another unusual flag for a really limited device

This version folds in Alan's example.

++doug
---
>From f644b337771374178d5585bcedf8153f5b45f2d6 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.

The lowest possible limit is PAGE_CACHE_SIZE, so if the device is ever
used on a platform that has larger than 8K pages, you lose unless you
can convince the device firmware folks to fix the issue.

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     |   12 +++++++++---
 drivers/usb/storage/unusual_devs.h |    7 +++++++
 include/linux/usb_usual.h          |    5 ++++-
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 1ba19ea..62e9e94 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -114,9 +114,15 @@ static int slave_configure(struct scsi_device *sdev)
 	 * while others have trouble with more than 64K. At this time we
 	 * are limiting both to 32K (64 sectores).
 	 */
-	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
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..a417b09 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,0x00002000)			\
+		/* 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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