linux-kernel - Re: [PATCH 00/22] Add and use pci_zalloc

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Message-ID: <1403550809.15811.13.camel@joe-AO725>
Date:	Mon, 23 Jun 2014 12:13:29 -0700
From:	Joe Perches <joe@...ches.com>
To:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-arch@...r.kernel.org, linux-scsi@...r.kernel.org,
	iss_storagedev@...com, linux-rdma@...r.kernel.org,
	netdev@...r.kernel.org, linux-atm-general@...ts.sourceforge.net,
	linux-wireless@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-crypto@...r.kernel.org, linux-eata@...onnect.net,
	linux-media@...r.kernel.org
Subject: Re: [PATCH 00/22] Add and use pci_zalloc_consistent

On Mon, 2014-06-23 at 10:25 -0700, Luis R. Rodriguez wrote:
> On Mon, Jun 23, 2014 at 06:41:28AM -0700, Joe Perches wrote:
> > Adding the helper reduces object code size as well as overall
> > source size line count.
> > 
> > It's also consistent with all the various zalloc mechanisms
> > in the kernel.
> > 
> > Done with a simple cocci script and some typing.
> 
> Awesome, any chance you can paste in the SmPL? Also any chance
> we can get this added to a make coccicheck so that maintainers
> moving forward can use that to ensure that no new code is
> added that uses the old school API?

Not many of these are recent.

Arnd Bergmann reasonably suggested that the pci_alloc_consistent
api be converted the the more widely used dma_alloc_coherent.

https://lkml.org/lkml/2014/6/23/513

> Shouldn't these drivers just use the normal dma-mapping API now?

and I replied:

https://lkml.org/lkml/2014/6/23/525

> Maybe.  I wouldn't mind.
> They do seem to have a trivial bit of unnecessary overhead for 
> hwdev == NULL ? NULL : &hwdev->dev

Anyway, here's the little script.
I'm not sure it's worthwhile to add it though.

$ cat ./scripts/coccinelle/api/alloc/pci_zalloc_consistent.cocci
///
/// Use pci_zalloc_consistent rather than
///     pci_alloc_consistent followed by memset with 0
///
/// This considers some simple cases that are common and easy to validate
/// Note in particular that there are no ...s in the rule, so all of the
/// matched code has to be contiguous
///
/// Blatantly cribbed from: scripts/coccinelle/api/alloc/kzalloc-simple.cocci

@@
type T, T2;
expression x;
expression E1,E2,E3;
statement S;
@@

- x = (T)pci_alloc_consistent(E1,E2,E3);
+ x = pci_zalloc_consistent(E1,E2,E3);
  if ((x==NULL) || ...) S
- memset((T2)x,0,E2);


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