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Thu, 20 Mar 2025 23:42:39 +0000 Message-ID: <99fe30bc-47cf-4910-bd80-3eb743ef0548@intel.com> Date: Thu, 20 Mar 2025 16:42:37 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/6] x86/microcode/intel_staging: Support mailbox data transfer To: Dave Hansen , CC: , , , , References: <20241001161042.465584-1-chang.seok.bae@intel.com> <20241211014213.3671-1-chang.seok.bae@intel.com> <20241211014213.3671-6-chang.seok.bae@intel.com> Content-Language: en-US From: "Chang S. 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It looks really > goofy to me, but I don't deal with devices much. Yeah, looking at some device code, functions like memcpy_toio() and __iowrite*_copy() seem to assume sufficient MMIO space to copy data from kernel memory. I also noticed that some other mailbox code calls back one of these functions. So, I think your assessment is correct: > To me, it's much more akin to talking over a serial port than how I > think of devices attached via MMIO. Certainly, this staging mailbox looks somewhat similar to a serial port. I suspect the staging portion is quite resource-limited. That appears to be one of key characteristics of this interface, which I should highlight more comprehensively. Thanks, Chang