[PATCH/RFC] usb: gadget: CONFIG_USB_S3C_HSOTG should depend on HAS_DMA

[PATCH/RFC] usb: gadget: CONFIG_USB_S3C_HSOTG should depend on HAS_DMA

[Geert Uytterhoeven]

If NO_DMA=y:

drivers/built-in.o: In function `s3c_hsotg_map_dma':
s3c-hsotg.c:(.text+0x375b2c): undefined reference to `usb_gadget_map_request'
drivers/built-in.o: In function `s3c_hsotg_unmap_dma':
s3c-hsotg.c:(.text+0x376a32): undefined reference to `usb_gadget_unmap_request'
make[3]: *** [vmlinux] Error 1

Note that all callers of s3c_hsotg_map_dma()/s3c_hsotg_unmap_dma() are
protected by a call into the using_dma() checking function:

static inline bool using_dma(struct s3c_hsotg *hsotg)
{
        return false;   /* support is not complete */
}

but not all versions of gcc manage to optimize the check away, causing a
link error.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Perhaps the DMA code should be removed completely, as its unused, or be
protected by #ifdef CONFIG_HAS_DMA instead?

 drivers/usb/gadget/Kconfig |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 3557c7e5040d..0e9dead51a27 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -302,6 +302,7 @@ config USB_PXA27X
 
 config USB_S3C_HSOTG
 	tristate "Designware/S3C HS/OtG USB Device controller"
+	depends on HAS_DMA
 	help
 	  The Designware USB2.0 high-speed gadget controller
 	  integrated into many SoCs.
-- 
1.7.9.5

RE: [PATCH/RFC] usb: gadget: CONFIG_USB_S3C_HSOTG should depend on HAS_DMA

[David Laight]

From: Geert Uytterhoeven
> If NO_DMA=y:
> 
> drivers/built-in.o: In function `s3c_hsotg_map_dma':
> s3c-hsotg.c:(.text+0x375b2c): undefined reference to `usb_gadget_map_request'
> drivers/built-in.o: In function `s3c_hsotg_unmap_dma':
> s3c-hsotg.c:(.text+0x376a32): undefined reference to `usb_gadget_unmap_request'
> make[3]: *** [vmlinux] Error 1
> 
> Note that all callers of s3c_hsotg_map_dma()/s3c_hsotg_unmap_dma() are
> protected by a call into the using_dma() checking function:
> 
> static inline bool using_dma(struct s3c_hsotg *hsotg)
> {
>         return false;   /* support is not complete */
> }
> 
> but not all versions of gcc manage to optimize the check away, causing a
> link error.

A have seen gcc optimise away a call, but leave the undefined symbol
in the symbol table.
That might be what is happening here.

I don't know a generic solution, I used 'objcopy -N__udivdi3' to remove
the explicit unwanted reference from my driver.

	David

Re: [PATCH/RFC] usb: gadget: CONFIG_USB_S3C_HSOTG should depend on HAS_DMA

[Geert Uytterhoeven]

Hi David,

On Tue, May 6, 2014 at 3:17 PM, David Laight <David.Laight@aculab.com> wrote:
>> If NO_DMA=y:
>>
>> drivers/built-in.o: In function `s3c_hsotg_map_dma':
>> s3c-hsotg.c:(.text+0x375b2c): undefined reference to `usb_gadget_map_request'
>> drivers/built-in.o: In function `s3c_hsotg_unmap_dma':
>> s3c-hsotg.c:(.text+0x376a32): undefined reference to `usb_gadget_unmap_request'
>> make[3]: *** [vmlinux] Error 1
>>
>> Note that all callers of s3c_hsotg_map_dma()/s3c_hsotg_unmap_dma() are
>> protected by a call into the using_dma() checking function:
>>
>> static inline bool using_dma(struct s3c_hsotg *hsotg)
>> {
>>         return false;   /* support is not complete */
>> }
>>
>> but not all versions of gcc manage to optimize the check away, causing a
>> link error.
>
> A have seen gcc optimise away a call, but leave the undefined symbol
> in the symbol table.
> That might be what is happening here.

Indeed, the unused functions s3c_hsotg_{,un}map_dma() are still there,
but the calls to them have been optimized away.

Marking s3c_hsotg_{,un}map_dma() inline fixes that. I'll send a new patch
doing that, as it's a bit silly to require "depends on HAS_DMA" for a driver
which has DMA disabled.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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