Hi Bob, Sorry for the late reply, I had being on holiday last few days. On 2013-9-18 23:09, Moore, Robert wrote: > > >> -----Original Message----- >> From: Hanjun Guo [mailto:hanjun.guo@xxxxxxxxxx] >> Sent: Wednesday, September 18, 2013 2:32 AM >> To: Moore, Robert >> Cc: 'Rafael J. Wysocki'; 'Len Brown'; Box, David E; Zheng, Lv; 'linux- >> acpi@xxxxxxxxxxxxxxx'; 'patches@xxxxxxxxxx'; 'linaro- >> kernel@xxxxxxxxxxxxxxxx'; 'linaro-acpi@xxxxxxxxxxxxxxxx' >> Subject: Re: [PATCH] ACPICA / hwreg: Use acpi_gbl_reduced_hardware to >> prevent accessing PM registers >> >> On 2013-9-17 1:26, Moore, Robert wrote: >>> + #define ACPI_REDUCED_HARDWARE TRUE >>> >>> The intent of this feature is of course, to remove all code that is not >> needed -- specifically for hardware-reduced machines where the size of the >> kernel is important. >>> >>> On a larger machine, the hardware-reduced flag should be sufficient. >> However, I would think that the host OS would look at this flag and >> realize that it should not be doing certain ACPI hardware-related things >> up front, rather than later when it finds out that a write to some ACPI >> hardware fails because the hardware isn't there. >> >> Do you mean we should change the ACPI device driver instead of changing >> the ACPICA code? that would be a hard job, because hardware ACPI is used >> everywhere. >> > > > I don't really know the answer to this, but something tells me that bad things > may happen when a driver expects the ACPI hardware to be there, and it finds > out that it isn't, simply by calling one of the ACPI hardware interfaces. > > Or, we could word it this way: if a driver is expecting the ACPI hardware to > exist, and we are running on a hardware-reduced platform, why is the driver > being loaded in the first place? ok, that would be a reasonable solution. Oh, things get complicated now, could some linux experts have comments here please? > > BTW, hardware-reduced is not restricted to ARM platforms. Thanks for reminding, may be some other platforms (not only x86, IA64, ARM) will use ACPI in the future. Thanks Hanjun > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
