• Linus Torvalds's avatar
    ALSA: update dell-wmi mic-mute registration to new world order · 70b20dd7
    Linus Torvalds authored
    Commit c647f806 ("ALSA: hda - Allow multiple ADCs for mic mute LED
    controls") changed the return value of the snd_hda_gen_add_micmute_led()
    without actually updating the callers.
    
    Admittedly, almost no callers actually cared about the return value.
    But one call site very much did: the Dell wmi code.  It would see the
    registration return zero, which _used_ to mean "failed" but now means
    "success", and clear the dell_micmute_led_set_func pointer.
    
    End result: the successful registration would end up calling the Dell
    code that thought it had all failed, and call through a NULL pointer.
    
    To make matters worse, it ends up being a tail-call, and with the
    retpoline sequence you don't even see the caller (dell_micmute_update())
    in the stack trace, so the error ended up way less obvious than it
    should have been.
    
    Fixes: c647f806 "ALSA: hda - Allow multiple ADCs for mic mute LED controls"
    Cc: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    70b20dd7
dell_wmi_helper.c 1.25 KB