On Fri, Jun 11, 2021 at 12:46 PM Shravan S <s.shravan@xxxxxxxxx> wrote: > > SAR (Specific Absorption Rate) driver is a host driver implemented for Linux > or chrome platform to limit the exposure of human body to RF frequency by informing > the Intel M.2 modem to regulate the RF power based on SAR data obtained from the sensors > captured in the BIOS. ACPI interface exposes this data from the BIOS to SAR driver. The > front end application in userspace ( eg: Modem Manager) will interact with SAR driver > to obtain information like the device mode (Example: tablets, laptops, etx), Antenna index, > baseband index, SAR table index and use available communication like MBIM interface to enable > data communication to modem for RF power regulation. > > The BIOS gets notified about device mode changes through Sensor Driver. This information is > given to a (newly created) WWAN ACPI function driver when there is a device mode change. > The driver then uses a _DSM method to retrieve the required information from BIOS. > This information is then forwarded/multicast to the User-space using the NETLINK interface. > A lookup table is maintained inside the BIOS which suggests the SAR Table index and Antenna > Tuner Table Index values for individual device modes. > > The SAR parameters to be used on the Modem differs for each Regulatory Mode like FCC, CE and ISED. > Hence, the SAR parameters are stored separately in the SMBIOS table in the OEM BIOS, > for each of the Regulatory mode. Regulatory modes will be different based on the region and network > available in that region. > > Hence the entire SAR functionality handling is divided into 2 parts: > > • A ACPI function driver implemented that uses a dedicated ACPI node for WWAN device. > sends notifications whenever there is change in Device Mode. (each OEM has different mechanism > of updating this DEVICE Mode info). This is notified to User-space applications using > the RT-NETLINK interface. > • WWAN Device Service listens for RT-NETLINK messages and routes them to Modem using MBIM. That's a nice feature! Why is it not a part of some generic subsubsystem under wireless network subsystem? -- With Best Regards, Andy Shevchenko
