Re: [PATCH 01/22] pci-dma-compat: Add pci_zalloc_consistent helper
From: Joe Perches
Date: Wed Jun 25 2014 - 17:51:59 EST
On Wed, 2014-06-25 at 12:27 -0700, Andrew Morton wrote:
> On Mon, 23 Jun 2014 06:41:29 -0700 Joe Perches <joe@xxxxxxxxxxx> wrote:
>
> > Add this helper for consistency with pci_zalloc_coherent
> > and the ability to remove unnecessary memset(,0,) uses.
>
> While we're being anal.. I'm not a big fan of the patch titles. Worst
> is "amd: Use pci_zalloc_consistent". "amd" is quite a poor identifier
> - it's only when you get in and look at the diff that you realise it's
> an ethernet driver.
Yeah, those "amd:" prefixes should really have been "pcnet32:"
> People sometimes address this by using
>
> "drivers: net: ethernet: amd: use pci_zalloc_consistent"
>
> which strikes me as utterly perverse. We already have a nice way of
> representing the hierarchy and that's using '/'.
I used to do that until several people complained.
Now I don't. btw: Documentation/SubmittingPatches says:
15) The canonical patch format
The canonical patch subject line is:
Subject: [PATCH 001/123] subsystem: summary phrase
> So when the irritation gets too high and when I can be bothered I'll
> rewrite things like that to
>
> "drivers/net/ethernet/amd: use pci_zalloc_consistent"
>
> which strikes me as being blindingly obvious, but apparently I'm in a
> small minority :(
>
> > --- a/include/asm-generic/pci-dma-compat.h
> > +++ b/include/asm-generic/pci-dma-compat.h
> > @@ -19,6 +19,14 @@ pci_alloc_consistent(struct pci_dev *hwdev, size_t size,
> > return dma_alloc_coherent(hwdev == NULL ? NULL : &hwdev->dev, size, dma_handle, GFP_ATOMIC);
> > }
> >
> > +static inline void *
> > +pci_zalloc_consistent(struct pci_dev *hwdev, size_t size,
> > + dma_addr_t *dma_handle)
> > +{
> > + return dma_zalloc_coherent(hwdev == NULL ? NULL : &hwdev->dev,
> > + size, dma_handle, GFP_ATOMIC);
> > +}
> > +
>
> We'd get a smaller kernel by uninlining this. It is hardly
> performance-sensitive. Uninlining would presumably use more stack,
> but GFP_ATOMIC won't use a ton of stack anyway.
True. Maybe via a follow-on patch.
Another option would be to remove pci_[z]alloc_consistent
and just use dma_alloc_coherent instead.
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