• H
    thinkpad-acpi: support the second fan on the X61 · d7377247
    Henrique de Moraes Holschuh 提交于
    Support reading the tachometer of the auxiliary fan of a X60/X61.
    
    It was found out by sheer luck, that bit 0 of EC register 0x31
    (formely HBRV) selects which fan is active for tachometer readings
    through EC 0x84/0x085: 0 for fan1, 1 for fan2.
    
    Many thanks to Christoph Kl??nter, to Whoopie, and to weasel, who
    helped confirm that behaviour.
    
    Fan control through EC HFSP applies to both fans equally, regardless
    of the state of bit 0 of EC 0x31.  That matches the way the DSDT uses
    HFSP.
    
    In order to better support the secondary fan, export a second
    tachometer over hwmon, and add defensive measures to make sure we are
    reading the correct tachometer.
    
    Support for the second fan is whitelist-based, as I have not found
    anything obvious to look for in the DSDT to detect the presence of
    the second fan.
    Signed-off-by: NHenrique de Moraes Holschuh <hmh@hmh.eng.br>
    Signed-off-by: NLen Brown <len.brown@intel.com>
    d7377247
thinkpad-acpi.txt 59.2 KB