linux-kernel - Re: xhci_hcd 3.12 regression

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Date:	Sun, 17 Nov 2013 02:13:22 +0000 (UTC)
From:	Nikolaus Meine <meine@....uni-hannover.de>
To:	linux-kernel@...r.kernel.org
Subject: Re: xhci_hcd 3.12 regression

Nikolaus Meine <meine <at> tnt.uni-hannover.de> writes:

> 
> After upgrading from kernel 3.11 to 3.12 my USB 3.0 card reader
> (Transcend RDF8) stopped working with the same error.
> 
> I managed to find the code line which triggered the erroneous behaviour:
> 
> It's the definition of the macro xhci_dbg(...) in xhci.h line 1590/1591.
> 
> In 3.11 it is
>   do { if (XHCI_DEBUG) dev_dbg(...); } while (0)
> 
> XHCI_DEBUG is defined as 0 because XHCI_HCD_DEBUGGING is not defined
> so this macro collapses to nothing.
> 
> In 3.12 xhci_dbg(...) is defined as
>   dev_dbg(...)
> which actually calls dev_printk(...) because DEBUG is defined.
> 
> If I define xhci_dbg() in 3.12 as
>   do { } while (0)
> my card reader starts working again.
> 
> That was the good news.
> The bad news is that I have no idea why calling dev_printk(...)
> does any  harm here. Maybe it's a timing problem.
> 
> Best Regards
> Nikolaus Meine
> 

Hello once again!

I have to correct me previous post:
The card reader does actually work with 3.12 so it's just
the dumping of debug messages which was enabled in 3.12,
no timing problem.

Best Regards
Nikolaus Meine


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