From 647a6002cb41d358d9ac5de101a8a6dc74748a59 Mon Sep 17 00:00:00 2001

From: Ian Abbott <abbotti@mev.co.uk>

Date: Wed, 21 Oct 2020 13:21:42 +0100

Subject: [PATCH] staging: comedi: cb_pcidas: Allow 2-channel commands for AO subdevice

Git-commit: 647a6002cb41d358d9ac5de101a8a6dc74748a59

Patch-mainline: v5.10-rc2

References: git-fixes

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>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 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 48ec2ee953dc..d740c4782775 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;

-- 

2.16.4