From mboxrd@z Thu Jan  1 00:00:00 1970
From: Venu Byravarasu <vbyravarasu@nvidia.com>
Subject: What is the significance of coherent_dma_mask?
Date: Wed, 8 Aug 2012 09:28:17 +0530
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	<lars@metafoo.de>, <grant.likely@secretlab.ca>, <joe@perches.com>
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Hi,

Some of the USB drivers are setting coherent_dma_mask & many others are 
not doing it.
 From the description present in the comment beside this field in 
device.h, I could not understand its real significance.

Can some one plz let me know its real need and use case where it is 
mandatory to use it?

Thanks,
Venu