Hi Andy, Why is it not a part of some generic subsystem under wireless network subsystem? -- This driver is instantiated only when the BIOS on given host exposes ACPI node corresponding to the BIOS SAR. This depends on support of the BIOS SAR feature by given OEM. -- It is agnostic of the wireless technology like WWAN, WiFi and BT. Hence, it is not made specific to any given wireless network subsystem. Please do let me know if you need more information. Thanks and Regards, Shravan S -----Original Message----- From: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> Sent: Sunday, June 13, 2021 7:52 PM To: Shravan, S <s.shravan@xxxxxxxxx> Cc: Hans de Goede <hdegoede@xxxxxxxxxx>; Mark Gross <mgross@xxxxxxxxxxxxxxx>; Platform Driver <platform-driver-x86@xxxxxxxxxxxxxxx>; An, Sudhakar <sudhakar.an@xxxxxxxxx> Subject: Re: [PATCH 0/1] [x86] BIOS SAR Driver for M.2 Intel Modems 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
