Re: [PATCH] ahci: qoriq: fixed using uninitialized variable warnings

[Tejun Heo <tj@kernel.org>]

On Wed, Sep 09, 2015 at 05:16:22PM +0800, Yuantian.Tang@freescale.com wrote:
> From: Tang Yuantian <Yuantian.Tang@freescale.com>
> 
> kbuild test robot reports the warnings:
> drivers/ata/ahci_qoriq.c: In function 'ahci_qoriq_hardreset':
> >> include/asm-generic/io.h:163:2: warning: 'px_is' may be used
> >> uninitialized in this function [-Wuninitialized]
> drivers/ata/ahci_qoriq.c:70:14: note: 'px_is' was declared here
> >> include/asm-generic/io.h:163:2: warning: 'px_cmd' may be used
> >> uninitialized in this function [-Wuninitialized]
> drivers/ata/ahci_qoriq.c:70:6: note: 'px_cmd' was declared here
> 
> This patch fixed it by assigning 0 to px_is and px_cmd variables.
> This patch also remove line 'struct ccsr_ahci *reg_base' which is
> not referred by any other codes and thus a dead one.

Hmm... I think the problem here is that the complier can't know
whether qoriq_priv->type would change across intervening function
calls.  Maybe a better solution is caching the type in a local
variable so that the compiler can tell that those two tests will
always move together?  It generally isn't a good idea to clear
variables unnecessarily as that can hide actual bugs that compiler can
detect.

Thanks.

-- 
tejun