Re: REGRESSION: usbdevfs: Use-scatter-gather-lists-for-large-bulk-transfers

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Hi,


On 10/12/2012 05:08 PM, Henrik Rydberg wrote:
Hi Alan,

Instead of introducing a new local variable, why not simply update
uurb->buffer?  That's what we do elsewhere in the code.

It seemed fragile, due to these scary lines:

	if (is_in && uurb->buffer_length > 0)
		as->userbuffer = uurb->buffer;
	else
		as->userbuffer = NULL;

I suppose it works in this particular case.  How is the
USBDEVFS_URB_TYPE_CONTROL case supposed to work here?

I can certainly change the patch if preferred. Tested and attached
below.

Thanks,
Henrik

 From 40b70394747eea51fdd07cc8213dd6afd24b1b30 Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@xxxxxxxxxxx>
Date: Thu, 11 Oct 2012 23:27:04 +0200
Subject: [PATCH v2] usbdevfs: Fix broken scatter-gather transfer

The handling of large output bulk transfers is broken; the same u
page is read over and over again. Fixed with this patch.

Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
---
  drivers/usb/core/devio.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index ebb8a9d..6e58b59 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1349,6 +1351,7 @@
  					goto error;
  				}
  			}
+			uurb->buffer += u;

I know you've already fixed this in the next revision, but still:

NAK, this will break large, split input transfers as it well
set as->userbuffer to the end of the buffer instead of the beginning!

Regards,

Hans
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