From 036695a65e4f4a731bce35cfc4ee6c05a86bd015 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 1 Mar 2021 16:57:57 +0000 Subject: [PATCH] staging: comedi: dt2814: Clear stale AI data on detach When the Comedi "detach" handler is called, it is possible that an extra A/D conversion (triggered during termination of a Comedi asynchronous command) is still in progress. In that case, the FINISH bit in the Status register will eventually get set and there will be stale data waiting to be read from the A/D Data register. The interrupt handler will also be called if still connected at the time. That should all be mostly harmless, but it would be better to wait for any such conversion to complete and clear any stale data during the "detach". Add a custom "detach" handler `dt2814_detach()` to do that if an interrupt handler has been set up. (There is no need to do it if no interrupt handler was set up because Comedi asynchronous command support is disabled in that case.) Signed-off-by: Ian Abbott Link: https://lore.kernel.org/r/20210301165757.243065-7-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/dt2814.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/staging/comedi/drivers/dt2814.c b/drivers/staging/comedi/drivers/dt2814.c index d18f9a5..ed44ce0 100644 --- a/drivers/staging/comedi/drivers/dt2814.c +++ b/drivers/staging/comedi/drivers/dt2814.c @@ -346,11 +346,24 @@ static int dt2814_attach(struct comedi_device *dev, struct comedi_devconfig *it) return 0; } +static void dt2814_detach(struct comedi_device *dev) +{ + if (dev->irq) { + /* + * An extra conversion triggered on termination of an + * asynchronous command may still be in progress. Wait for + * it to finish and clear the data or error status. + */ + dt2814_ai_clear(dev); + } + comedi_legacy_detach(dev); +} + static struct comedi_driver dt2814_driver = { .driver_name = "dt2814", .module = THIS_MODULE, .attach = dt2814_attach, - .detach = comedi_legacy_detach, + .detach = dt2814_detach, }; module_comedi_driver(dt2814_driver); -- 2.7.4