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Subject: Re: [PATCH] rtc: pl030: Use devm_kzalloc() instead of kmalloc()
From: Joe Perches <joe@perches.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "sangjung.woo" <sangjung.woo@samsung.com>,
        Alessandro Rubini <rubini@gnudd.com>,
        Russell King <rmk+kernel@arm.linux.org.uk>, rtc-linux@googlegroups.com,
        linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
        Greg KH <greg@kroah.com>
Date: Thu, 10 Oct 2013 16:14:00 -0700
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On Thu, 2013-10-10 at 16:06 -0700, Andrew Morton wrote:
> On Tue, 08 Oct 2013 21:59:27 -0700 Joe Perches <joe@perches.com> wrote:
> 
> > I was a bit surprised to find there isn't a devm_kmalloc.
> 
> Yes, the unconditional memset is silly.  Especially when the
> function has a handy gfp_t and could be passed __GFP_ZERO.
> 
> The comment says "managed kzalloc/kfree for device drivers, no kmalloc,
> always use kzalloc".  There's no explanation for this - it looks like
> some ideological thing.

Try this patch instead:
https://lkml.org/lkml/2013/10/9/14

Yours has an unnecessary duplicate memset of the whole
block when __GFP_ZERO is passed when that's already
done by the kmalloc_track_caller allocator.

Also if __GFP_ZERO is not passed, you should still
zero the struct devres header.