linux-kernel - dma_debug_device_change() gives bogus errors

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Date:	Fri, 24 Apr 2009 12:20:04 +0100
From:	David Vrabel <david.vrabel@....com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: dma_debug_device_change() gives bogus errors

dma_debug_device_change() gives bogus errors if a driver unmaps dma
buffers within its driver->remove() method.  This is because the
BUS_NOTIFY_UNBIND_DRIVER notification is raised before calling
driver->remove() (see __device_release_driver() in drivers/base/dd.c).

By the time my driver->remove() completes, there are no DMA mappings
(debug_dma_dump_mappings() produces no output).

Also, somewhat surprisingly, it only prints the error the first time the
driver is unbound.

David
-- 
David Vrabel, Senior Software Engineer, Drivers
CSR, Churchill House, Cambridge Business Park,  Tel: +44 (0)1223 692562
Cowley Road, Cambridge, CB4 0WZ                 http://www.csr.com/
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