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Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc()

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On Tue, Aug 25, 2015 at 01:43:58PM -0700, Andrew Morton wrote:
> On Tue, 25 Aug 2015 17:48:37 +0200 "Luis R. Rodriguez" <mcgrof@suse.com> wrote:
> 
> > On Tue, Aug 25, 2015 at 09:53:18AM +0200, Ingo Molnar wrote:
> > > Which kernel is this against? It has conflicts in 3 files with Linus's latest: 
> > > v4.2-rc8.
> > 
> > Sorry I based it on linux-next, will respin the rename patch onto tip/auto-latest
> > 
> 
> Doing that will make the patch kinda useless, because then the patch
> will trash more mature work which is pending in linux-next, one week
> before the merge window opens.
> 
> A better plan would be to base the patches on linux-next then wait for
> 4.3-rc1.

There's a catch-22 issue here either way, for instance this rename
patch has been being baked for probably 2 releases already but the
difficulty has been trying to find the appropriate time to merge it
without conflict.

If you do it in the beginning of the merge window, you have to ask
yourself in what tree it will be done. Since subsystems are topic
specific that means that subsystem will end up having a conflict
at the end of the merge window.

If you do it at the end you run into the issue you describe.

So unless I'm missing something, perhaps metrics to argue one way is better
than another, it seems today this is up up to a subsystem's maintainer's
preference?

There are more subtle issues with this though, I've identified similar problems
before and proposed one solution to it could be a linux-oven [0], in that
thread I describe other issues and why I think a linux-oven might help.

Perhaps the biggest change that comes to mind that could have caused
tons of collateral was the UAPI change David Howells did years ago,
when did that go in, at the end of early? In retrospect what would have
helped?

Anyway, both version of the patch are now available, up to you guys :)

[0] http://lkml.kernel.org/r/20150619231255.GC7487@garbanzo.do-not-panic.com

  Luis
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[PATCH v4 00/11] x86/dma: RIP MTRR and dma write-combine API rename "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:20 +0200
  [PATCH v4 01/11] PCI: Add pci_ioremap_wc_bar() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:20 +0200
    [tip:x86/mm] PCI: Add pci_ioremap_wc_bar() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 02/11] drivers/video/fbdev/i740fb: Use arch_phys_wc_add() and pci_ioremap_wc_bar() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:20 +0200
    [tip:x86/mm] drivers/video/fbdev/i740fb: Use arch_phys_wc_add()   and pci_ioremap_wc_bar() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 03/11] drivers/video/fbdev/kyrofb: Use arch_phys_wc_add() and pci_ioremap_wc_bar() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/video/fbdev/kyrofb: Use arch_phys_wc_add()   and pci_ioremap_wc_bar() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 05/11] PCI: Add pci_iomap_wc() variants "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] PCI: Add pci_iomap_wc() variants "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 08/11] drivers/video/fbdev/vt8623fb: Use arch_phys_wc_add() and pci_iomap_wc() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/video/fbdev/vt8623fb: Use arch_phys_wc_add()   and pci_iomap_wc() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 11/11] mtrr: bury MTRR - unexport mtrr_add() and mtrr_del() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] x86/mm/mtrr: Remove kernel internal MTRR interfaces:   unexport mtrr_add() and mtrr_del() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-28 10:20 +0200
  [PATCH v4 09/11] drivers/dma/iop-adma: Use dma_alloc_writecombine() kernel-style "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/dma/iop-adma: Use dma_alloc_writecombine()   kernel-style "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 04/11] drivers/video/fbdev/gxt4500: Use pci_ioremap_wc_bar() to map framebuffer "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/video/fbdev/gxt4500: Use pci_ioremap_wc_bar(  ) to map framebuffer "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 07/11] drivers/video/fbdev/s3fb: Use arch_phys_wc_add() and pci_iomap_wc() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/video/fbdev/s3fb: Use arch_phys_wc_add()   and pci_iomap_wc() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  [PATCH v4 06/11] drivers/video/fbdev/arkfb.c: Use arch_phys_wc_add() and pci_iomap_wc() "Luis R. Rodriguez" <mcgrof@do-not-panic.com> - 2015-08-24 21:30 +0200
    [tip:x86/mm] drivers/video/fbdev/arkfb.c: Use arch_phys_wc_add()   and pci_iomap_wc() "tip-bot for Luis R. Rodriguez" <tipbot@zytor.com> - 2015-08-25 10:30 +0200
  Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() Ingo Molnar <mingo@kernel.org> - 2015-08-25 10:20 +0200
    Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() "Luis R. Rodriguez" <mcgrof@suse.com> - 2015-08-25 17:50 +0200
      Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() Andrew Morton <akpm@linux-foundation.org> - 2015-08-25 22:50 +0200
        Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() "Luis R. Rodriguez" <mcgrof@suse.com> - 2015-08-26 01:20 +0200
          Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() Andrew Morton <akpm@linux-foundation.org> - 2015-08-26 01:30 +0200
            Re: [PATCH v4 10/11] dma: rename dma_*_writecombine() to dma_*_wc() Ingo Molnar <mingo@kernel.org> - 2015-08-26 06:30 +0200

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