From: Ian Abbott <abbotti@mev.co.uk> stable inclusion from linux-4.19.155 commit 28f7c57a3ce95ca17cff98cc5af52fe7f9226f3f -------------------------------- commit 647a6002cb41d358d9ac5de101a8a6dc74748a59 upstream. The "cb_pcidas" driver supports asynchronous commands on the analog output (AO) subdevice for those boards that have an AO FIFO. The code (in `cb_pcidas_ao_check_chanlist()` and `cb_pcidas_ao_cmd()`) to validate and set up the command supports output to a single channel or to two channels simultaneously (the boards have two AO channels). However, the code in `cb_pcidas_auto_attach()` that initializes the subdevices neglects to initialize the AO subdevice's `len_chanlist` member, leaving it set to 0, but the Comedi core will "correct" it to 1 if the driver neglected to set it. This limits commands to use a single channel (either channel 0 or 1), but the limit should be two channels. Set the AO subdevice's `len_chanlist` member to be the same value as the `n_chan` member, which will be 2. Cc: <stable@vger.kernel.org> Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Link: https://lore.kernel.org/r/20201021122142.81628-1-abbotti@mev.co.uk Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/staging/comedi/drivers/cb_pcidas.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/staging/comedi/drivers/cb_pcidas.c b/drivers/staging/comedi/drivers/cb_pcidas.c index 8429d57087fd..9b716c696477 100644 --- a/drivers/staging/comedi/drivers/cb_pcidas.c +++ b/drivers/staging/comedi/drivers/cb_pcidas.c @@ -1342,6 +1342,7 @@ static int cb_pcidas_auto_attach(struct comedi_device *dev, if (dev->irq && board->has_ao_fifo) { dev->write_subdev = s; s->subdev_flags |= SDF_CMD_WRITE; + s->len_chanlist = s->n_chan; s->do_cmdtest = cb_pcidas_ao_cmdtest; s->do_cmd = cb_pcidas_ao_cmd; s->cancel = cb_pcidas_ao_cancel; -- 2.25.1