[PATCH/RFC 0/6] Allow compile-testing NO_DMA

[Geert Uytterhoeven]

	Hi all,

If NO_DMA=y, get_dma_ops() returns a reference to the non-existing
symbol bad_dma_ops, thus causing a link failure if it is ever used.

The intention of this is twofold:
  1. To catch users of the DMA API on systems that do no support the DMA
     mapping API,
  2. To avoid building drivers that cannot work on such systems anyway.

However, the disadvantage is that we have to keep on adding dependencies
on HAS_DMA all over the place.

Thanks to the COMPILE_TEST symbol, lots of drivers now depend on one or
more platform dependencies (that imply HAS_DMA) || COMPILE_TEST, thus
already covering intention #2.  Having to add an explicit dependency on
HAS_DMA here is cumbersome, and hinders compile-testing.

Hence I think the time is ripe to reconsider the link failure.
This patch series:
  - Changes get_dma_ops() to return NULL instead,
  - Adds a few more dummies to enable compile-testing,
  - Removes dependencies on HAS_DMA for symbols that already have
    platform dependencies implying HAS_DMA.

Note that adding more platform dependencies and/or dependencies on
COMPILE_TEST is encouraged!

This may make life harder for UML, though, as UML usually satisfies all
other platform dependencies for HAS_DMA.  Similarly, HAS_IOMEM is even
more complicated.  Can/do we want to do something similar for
HAS_IOMEM?

This series is against my current local tree, which has a few more
"depends on HAS_DMA" than upstream.  Of course I will rebase, and split
the last patch per subsystem, if this RFC is welcomed positively.

Compile-tested with allmodconfig and allyesconfig for m68k/sun3.

Thanks for your comments!

Geert Uytterhoeven (6):
  [RFC] dma-mapping: Convert NO_DMA get_dma_ops() into a real dummy
  [RFC] dma-coherent: Add NO_DMA dummies for managed DMA API
  [RFC] usb: gadget: Add NO_DMA dummies for DMA mapping API
  [RFC] mm: Add NO_DMA dummies for DMA pool API
  [RFC] scsi: Add NO_DMA dummies for SCSI DMA mapping API
  [RFC] Treewide: Remove depends on HAS_DMA in case of platform
    dependency

 drivers/ata/Kconfig                             |  2 --
 drivers/crypto/Kconfig                          | 14 +++------
 drivers/firewire/Kconfig                        |  1 -
 drivers/fpga/Kconfig                            |  1 -
 drivers/gpu/ipu-v3/Kconfig                      |  1 -
 drivers/i2c/busses/Kconfig                      |  3 --
 drivers/iio/adc/Kconfig                         |  3 --
 drivers/iommu/Kconfig                           |  5 ++--
 drivers/lightnvm/Kconfig                        |  2 +-
 drivers/mailbox/Kconfig                         |  2 --
 drivers/media/pci/dt3155/Kconfig                |  1 -
 drivers/media/pci/solo6x10/Kconfig              |  1 -
 drivers/media/pci/sta2x11/Kconfig               |  1 -
 drivers/media/pci/tw5864/Kconfig                |  1 -
 drivers/media/pci/tw686x/Kconfig                |  1 -
 drivers/media/platform/Kconfig                  | 40 ++++++++-----------------
 drivers/media/platform/am437x/Kconfig           |  2 +-
 drivers/media/platform/atmel/Kconfig            |  4 +--
 drivers/media/platform/blackfin/Kconfig         |  1 -
 drivers/media/platform/davinci/Kconfig          |  6 ----
 drivers/media/platform/marvell-ccic/Kconfig     |  3 +-
 drivers/media/platform/rcar-vin/Kconfig         |  2 +-
 drivers/media/platform/soc_camera/Kconfig       |  3 +-
 drivers/media/platform/sti/c8sectpfe/Kconfig    |  2 +-
 drivers/mmc/host/Kconfig                        | 10 ++-----
 drivers/mtd/nand/Kconfig                        |  8 ++---
 drivers/mtd/spi-nor/Kconfig                     |  2 +-
 drivers/net/ethernet/amd/Kconfig                |  2 +-
 drivers/net/ethernet/apm/xgene-v2/Kconfig       |  1 -
 drivers/net/ethernet/apm/xgene/Kconfig          |  1 -
 drivers/net/ethernet/arc/Kconfig                |  6 ++--
 drivers/net/ethernet/broadcom/Kconfig           |  2 --
 drivers/net/ethernet/calxeda/Kconfig            |  2 +-
 drivers/net/ethernet/hisilicon/Kconfig          |  2 +-
 drivers/net/ethernet/marvell/Kconfig            |  8 ++---
 drivers/net/ethernet/mellanox/mlxsw/Kconfig     |  2 +-
 drivers/net/ethernet/renesas/Kconfig            |  2 --
 drivers/net/ethernet/socionext/Kconfig          |  4 +--
 drivers/net/wireless/broadcom/brcm80211/Kconfig |  1 -
 drivers/net/wireless/quantenna/qtnfmac/Kconfig  |  2 +-
 drivers/remoteproc/Kconfig                      |  1 -
 drivers/scsi/hisi_sas/Kconfig                   |  2 +-
 drivers/spi/Kconfig                             | 12 ++------
 drivers/staging/media/davinci_vpfe/Kconfig      |  1 -
 drivers/staging/media/omap4iss/Kconfig          |  1 -
 drivers/staging/vc04_services/Kconfig           |  1 -
 drivers/tty/serial/Kconfig                      |  4 ---
 drivers/usb/gadget/udc/Kconfig                  |  4 +--
 drivers/usb/mtu3/Kconfig                        |  2 +-
 drivers/video/fbdev/Kconfig                     |  3 +-
 include/linux/dma-mapping.h                     | 19 ++++++++----
 include/linux/dmapool.h                         | 21 +++++++++++--
 include/linux/usb/gadget.h                      | 12 ++++++++
 include/scsi/scsi_cmnd.h                        |  5 ++++
 sound/soc/bcm/Kconfig                           |  3 +-
 sound/soc/kirkwood/Kconfig                      |  1 -
 sound/soc/pxa/Kconfig                           |  1 -
 sound/soc/qcom/Kconfig                          |  6 ++--
 58 files changed, 108 insertions(+), 148 deletions(-)

-- 
2.7.4

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds