patch "staging: comedi: ni_routes: allow partial routing information" added to staging-linus

This is a note to let you know that I've just added the patch titled

staging: comedi: ni_routes: allow partial routing information

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 9fea3a40f6b07de977a2783270c8c3bc82544d45 Mon Sep 17 00:00:00 2001
From: Ian Abbott <[email protected]>
Date: Tue, 14 Jan 2020 18:25:32 +0000
Subject: staging: comedi: ni_routes: allow partial routing information

This patch fixes a regression on setting up asynchronous commands to use external trigger sources when board-specific routing information is missing.

ni_find_device_routes() (called via ni_assign_device_routes()) finds the table of register values for the device family and the set of valid routes for the specific board. If both are found, tables->route_values is set to point to the table of register values for the device family and tables->valid_routes is set to point to the list of valid routes for the specific board. If either is not found, both tables->route_values and tables->valid_routes are left set at their initial null values (initialized by ni_assign_device_routes()) and the function returns -ENODATA.

Returning an error results in some routing functionality being disabled. Unfortunately, leaving table->route_values set to NULL also breaks the setting up of asynchronous commands that are configured to use external trigger sources. Calls to ni_check_trigger_arg() or ni_check_trigger_arg_roffs() while checking the asynchronous command set-up would result in a null pointer dereference if table->route_values is NULL. The null pointer dereference is fixed in another patch, but it now results in failure to set up the asynchronous command. That is a regression from the behavior prior to commit 347e244884c3 ("staging: comedi: tio: implement global tio/ctr routing") and commit 56d0b826d39f ("staging: comedi: ni_mio_common:
implement new routing for TRIG_EXT").

Change ni_find_device_routes() to set tables->route_values and/or tables->valid_routes to valid information even if the other one can only be set to NULL due to missing information. The function will still return an error in that case. This should result in tables->valid_routes being valid for all currently supported device families even if the board-specific routing information is missing. That should be enough to fix the regression on setting up asynchronous commands to use external triggers for boards with missing routing information.

---
 drivers/staging/comedi/drivers/ni_routes.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

index 9627bd1d2a78..8f398b30f5bf 100644
@@ -72,9 +72,6 @@ static int ni_find_device_routes(const char *device_family,
 		}
 	}
 
-	if (!rv)
-		return -ENODATA;
-
 	/* Second, find the set of routes valid for this device. */
 	for (i = 0; ni_device_routes_list[i]; ++i) {
 		if (memcmp(ni_device_routes_list[i]->device, board_name,

@@ -84,12 +81,12 @@ static int ni_find_device_routes(const char *device_family,
 		}
 	}
 
-	if (!dr)
-		return -ENODATA;
-
 	tables->route_values = rv;
 	tables->valid_routes = dr;
 
+	if (!rv || !dr)
+		return -ENODATA;
+
 	return 0;
 }
 

2.24.1