Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx> writes: > CSME in two words > ----------------- > CSME stands for Converged Security and Management Engine. It is > a CPU on the chipset and runs a dedicated firmware. > AMT (Active Management Technology) is one of the applications > that run on that CPU. AMT allows to control the platform remotely. > Here is a partial list of the use cases: > * View the screen of the plaform, with keyboard and mouse (KVM) > * Attach a remote IDE device > * Have a serial console to the device > * Query the state of the platform > * Reset / shut down / boot the platform > > Networking in CSME > ------------------ > For those uses cases, CSME's firmware has an embedded network > stack and is able to use the network devices of the system: LAN > and WLAN. This is thanks to the CSME's firmware WLAN driver. > > One can add a profile (SSID / key / certificate) to the CSME's OS > and CSME will connect to that profile. Then, one can use the WLAN > link to access the applications that run on CSME (AMT is one of > them). Note that CSME is active during power state and power state > transitions. For example, it is possible to have a KVM session > open to the system while the system is rebooting and actually > configure the BIOS remotely over WLAN thanks to AMT. > > How all this is related to Linux > -------------------------------- > In Linux, there is a driver that allows the OS to talk to the > CSME firmware, this driver is drivers/misc/mei. This driver > advertises a bus that allows other kernel drivers or even user > space) to talk to components inside the CSME firmware. > In practice, the system advertises a PCI device that allows > to send / receive data to / from the CSME firmware. The mei > bus drivers in drivers/misc/mei is an abstration on top of > this PCI device. > The driver being added here is called iwlmei and talks to the > WLAN driver inside the CSME firmware through the mei bus driver. > Note that the mei bus driver only gives bus services, it doesn't > define the content of the communication. > > Why do we need this driver? > -------------------------- > CSME uses the same WLAN device that the OS is expecting to see > hence we need an arbitration mechanism. This is what iwlmei is > in charge of. iwlmei maintains the communication with the CSME > firmware's WLAN driver. The language / protocol that is used > between the CSME's firmware WLAN driver and iwlmei is OS agnostic > and is called SAP which stands for Software Abritration Protocol. > With SAP, iwlmei will be able to tell the CSME firmware's WLAN > driver: > 1) Please give me the device. > 2) Please note that the SW/HW rfkill state change. > 3) Please note that I am now associated to X. > 4) Please note that I received this packet. > etc... > > There are messages that go the opposite direction as well: > 1) Please note that AMT is en/disable. > 2) Please note that I believe the OS is broken and hence I'll take > the device *now*, whether you like it or not, to make sure that > connectivity is preserved. > 3) Please note that I am willing to give the device if the OS > needs it. > 4) Please give me any packet that is sent on UDP / TCP on IP address > XX.XX.XX.XX and an port ZZ. > 5) Please send this packet. > etc... > > Please check drivers/net/wireless/intel/iwlwifi/mei/sap.h for the > full protocol specification. > > Arbitration is not the only purpose of iwlmei and SAP. SAP also > allows to maintain the AMT's functionality even when the OS owns > the device. To connect to AMT, one needs to initiate an HTTP > connection to port 16992. iwlmei will listen to the Rx path and > forward (through SAP) to the CSME firmware the data it got. Then, > the embedded HTTP server in the chipset will reply to the request > and send a SAP notification to ask iwlmei to send the reply. > This way, AMT running on the CSME can still work. > > In practice this means that all the use cases quoted above (KVM, > remote IDE device, etc...) will work even when the OS uses the > WLAN device. > > How to disable all this? > --------------------------- > iwlmei won't be able to do anything if the CSME's networking stack > is not enabled. By default, CSME's networking stack is disabled (this > is a BIOS setting). > In case the CSME's networking stack is disabled, iwlwifi will just > get access to the device because there is no contention with any other > actor and, hence, no arbitration is needed. > > In this patch, I only add the iwlmei driver. Integration with > iwlwifi will be implemented in the next one. > > Co-Developed-by: Ayala Beker <ayala.beker@xxxxxxxxx> > Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx> s-o-b missing from Ayala, same problem also in other patches in this patchset. https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
