• Richard Cochran's avatar
    ptp: Avoid deadlocks in the programmable pin code. · 62582a7e
    Richard Cochran authored
    The PTP Hardware Clock (PHC) subsystem offers an API for configuring
    programmable pins.  User space sets or gets the settings using ioctls,
    and drivers verify dialed settings via a callback.  Drivers may also
    query pin settings by calling the ptp_find_pin() method.
    
    Although the core subsystem protects concurrent access to the pin
    settings, the implementation places illogical restrictions on how
    drivers may call ptp_find_pin().  When enabling an auxiliary function
    via the .enable(on=1) callback, drivers may invoke the pin finding
    method, but when disabling with .enable(on=0) drivers are not
    permitted to do so.  With the exception of the mv88e6xxx, all of the
    PHC drivers do respect this restriction, but still the locking pattern
    is both confusing and unnecessary.
    
    This patch changes the locking implementation to allow PHC drivers to
    freely call ptp_find_pin() from their .enable() and .verify()
    callbacks.
    
    V2 ChangeLog:
    - fixed spelling in the kernel doc
    - add Vladimir's tested by tag
    Signed-off-by: default avatarRichard Cochran <richardcochran@gmail.com>
    Reported-by: default avatarYangbo Lu <yangbo.lu@nxp.com>
    Tested-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    62582a7e
dp83640.c 38.3 KB