Hi Vegard, On Mon, Feb 15, 2016 at 11:41 AM, Vegard Nossum <vegard.nossum@xxxxxxxxxx> wrote: > Some platforms don't have DMA, but we should still be able to build > USB drivers for these platforms. They could still be used through > vhci_hcd, usbip_host, or maybe something like USB passthrough in UML > from a capable host. > > This is admittedly ugly with the #ifdefs, but those are necessary to > get around linker errors like these: > > drivers/built-in.o: In function `dma_unmap_sg_attrs': > include/linux/dma-mapping.h:183: undefined reference to `bad_dma_ops' > drivers/built-in.o: In function `dma_unmap_single_attrs': > include/linux/dma-mapping.h:148: undefined reference to `bad_dma_ops' > drivers/built-in.o: In function `dma_map_sg_attrs': > include/linux/dma-mapping.h:168: undefined reference to `bad_dma_ops' > drivers/built-in.o: In function `dma_map_page': > include/linux/dma-mapping.h:196: undefined reference to `bad_dma_ops' > drivers/built-in.o: In function `dma_mapping_error': > include/linux/dma-mapping.h:430: undefined reference to `bad_dma_ops' > drivers/built-in.o:include/linux/dma-mapping.h:131: more undefined references to `bad_dma_ops' follow > > Greg KG suggested just defining these for UML [1] but according to > Richard Weinberger this has come up before and it was decided not to > do that just for the sake of making drivers build [2]. > > [1]: http://www.spinics.net/lists/linux-usb/msg136306.html > [2]: http://www.spinics.net/lists/linux-usb/msg136308.html > > If any of the new warnings trigger, the correct solution is almost > certainly to add a CONFIG_HAS_DMA dependency in the Kconfig menu for > the responsible driver -- that driver's functions will hopefully > appear somewhere in the stack trace. > > v2: Reduce the number of #ifdefs by moving code out into helpers. > > Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> I have an even smaller patch that I've been updating over the years to compile allmodconfig/allyesconfig kernels for m68k/Sun-3. I'll clean it up and send it... 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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
