On 06/26/2013 05:03 PM, Richard Weinberger wrote: > Am 26.06.2013 10:58, schrieb Chen Gang: >> > On 06/26/2013 04:39 PM, Richard Weinberger wrote: >>>>>>>>>>> >>>>>>>>>> The drivers internal code has already check the related return value, >>>>>>>>>>> >>>>>>>>>> so it is the architecture's duty to 'tell' the driver whether support >>>>>>>>>>> >>>>>>>>>> io memory (e.g. define ioremap, but return NULL). >>>>>>> >>>>>> It does so already by setting CONFIG_HAS_IOMEM=n >>>>> >>>> >>>>> >>>> Excuse me, I use "grep -rn ioremap *" under "include/" and "arch/um/" >>>>> >>>> directory, but can not find the related definition for 'ioremap'. >>>>> >>>> >>>>> >>>> Is there another declaration or definition way which I don't know ? >>>>> >>>> (maybe it is). >>> >> Both UML and s390 (in the !CONFIG_PCI) do not define ioremap() because >>> >> without io memory you cannot have a ioremap(). >>> >> >> > >> > I assume if ioremap() return NULL, it means "without io memory", is it >> > correct ? >> > >> > If it is correct, "define a dummy ioremap(), and return NULL" is just >> > the meaning that you mentioned above. >> > >> > If so, for UML, it is not requirement, but recommend to define a dummy >> > ioremap() which return NULL, so can be generic enough to mach all cases. > No. > Not setting CONFIG_HAS_IOMEM=y means "This arch has no io memory and therefore no > functions to mess with it". > Since the API itself already contents the meaning: "return NULL means the arch has no related io memory", Why not define a generic dummy one in "include/asm-generic/io.h" instead of "HAS_IOMEM" (which has already spread many various places, and also, most of new drivers have to know about it). e.g: in "include/asm-generic/io.h", if "CONFIG_HAS_IOMEM=n", define a dummy ioremap() which return NULL ... (also need consider more details). All together, I think: it is the duty of "asm-generic/io.h" to process this issue, not the duty of many drivers and some architectures. > Let's get back to the real problem, > drivers/ptp/ptp_pch.c does not build on UML (and I'm very sure also not on S390). > Fix the issue by making it depend on HAS_IOMEM. > At least now, it seems it is the only suitable way to fix this issue. :-( > Btw: Did you actually look at this driver? There is *zero* reason to have it on UML. > ..like 99.9% of all other drivers which use io memory. Excuse me, I did not look at the details of this driver. Maybe it just like you said above. Thanks. -- Chen Gang Asianux Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
