On Wed, 2014-06-25 at 12:27 -0700, Andrew Morton wrote:

On Mon, 23 Jun 2014 06:41:29 -0700 Joe Perches [off-list ref] wrote:

quoted

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 :(

quoted

--- 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.