Re: [PATCH 01/11] ARM: disable virt_to_bus/virt_to_bus almost everywhere

[James Hogan]

On 14 February 2013 13:49, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> We are getting a number of warnings about the use of the deprecated
> bus_to_virt function in drivers using the ARM ISA DMA API:
>
> drivers/parport/parport_pc.c: In function 'parport_pc_fifo_write_block_dma':
> drivers/parport/parport_pc.c:622:3: warning: 'bus_to_virt' is deprecated
> (declared at arch/arm/include/asm/memory.h:253) [-Wdeprecated-declarations]
>
> This is only because that function gets used by the inline
> set_dma_addr() helper. We know that any driver for the ISA DMA API
> is correctly using the DMA addresses, so we can change this
> to use the __bus_to_virt() function instead, which does not warn.
>
> After this, there are no remaining drivers that are used on
> any defconfigs on ARM using virt_to_bus or bus_to_virt, with
> the exception of the OSS sound driver. That driver is only used
> on RiscPC, NetWinder and Shark, so we can set ARCH_NO_VIRT_TO_BUS
> on all other platforms and hide the deprecated functions, which
> is far more effective than marking them as deprecated, in order
> to avoid any new users of that code.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> ---
>  arch/arm/Kconfig                 | 4 ++++
>  arch/arm/configs/shark_defconfig | 1 -
>  arch/arm/include/asm/dma.h       | 2 +-
>  arch/arm/include/asm/memory.h    | 2 ++
>  4 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 67874b8..91d4aea 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1450,6 +1450,10 @@ config ISA_DMA
>         bool
>         select ISA_DMA_API
>
> +config ARCH_NO_VIRT_TO_BUS
> +       def_bool y
> +       depends on !ARCH_RPC && !ARCH_NETWINDER && !ARCH_SHARK

Hi Arnd,

There's a patch in linux-next by Stephen Rothwell "Centralise
CONFIG_ARCH_NO_VIRT_TO_BUS" that removes this Kconfig symbol,
inverting/replacing it with "select HAVE_VIRT_TO_BUS" (including for
arch/arm) which will undo the effects of this.

Cheers
James
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