linux-kernel - Re: [PATCH v2] USB: host: Use zeroing memory allocator rather than allocator/memset

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Date:   Mon, 1 Jan 2018 19:21:51 +0530
From:   Himanshu Jha <himanshujha199640@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     gregkh@...uxfoundation.org, mathias.nyman@...el.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        mcgrof@...nel.org
Subject: Re: [PATCH v2] USB: host: Use zeroing memory allocator rather than
 allocator/memset

On Sun, Dec 31, 2017 at 04:20:45PM -0500, Alan Stern wrote:
> On Sun, 31 Dec 2017, Himanshu Jha wrote:
> 
> > Use dma_zalloc_coherent for allocating zeroed
> > memory and remove unnecessary memset function.
> > 
> > Done using Coccinelle.
> > Generated-by: scripts/coccinelle/api/alloc/kzalloc-simple.cocci
> > 0-day tested with no failures.
> > 
> > Suggested-by: Luis R. Rodriguez <mcgrof@...nel.org>
> > Signed-off-by: Himanshu Jha <himanshujha199640@...il.com>
> > ---
> > v2:
> >    -align argumenst as they were before applying the SmPL rule.
> 
> For the UHCI portion:
> 
> Acked-by: Alan Stern <stern@...land.harvard.edu>
> 
> But there is something pecular about the patch...
> 
> >  drivers/usb/host/uhci-hcd.c | 7 +++----
> >  drivers/usb/host/xhci-mem.c | 7 ++-----
> >  2 files changed, 5 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c
> > index f5c9021..ac53398 100644
> > --- a/drivers/usb/host/uhci-hcd.c
> > +++ b/drivers/usb/host/uhci-hcd.c
> > @@ -600,15 +600,14 @@ static int uhci_start(struct usb_hcd *hcd)
> >  	uhci->dentry = dentry;
> >  #endif
> >  
> > -	uhci->frame = dma_alloc_coherent(uhci_dev(uhci),
> > -			UHCI_NUMFRAMES * sizeof(*uhci->frame),
> > -			&uhci->frame_dma_handle, GFP_KERNEL);
> > +	uhci->frame = dma_zalloc_coherent(uhci_dev(uhci),
> > +			UHCI_NUMFRAMES * sizeof(*uhci->frame),
> > +			&uhci->frame_dma_handle, GFP_KERNEL);
> 
> The second and third "changed" lines here actually are identical.  What 
> program would produce a diff file showing that they were changed?

I'm sorry, I can't understand the problem.
The patch was generated by cocci script specified above and then you
told me to change the whitespace scheme as it was before. It is also
0-day tested as specified above. It's also free from warnings reported by
checkpatch.

If are still confused please take a look at the rule :
https://lkml.org/lkml/2017/12/26/205
which will be soon merged to the linux-next tree.

Thanks
Himanshu Jha