Factorise the databittiming validation out of can_validate() and move
it in the new add can_validate_databittiming() function. This is a
preparation patch for the introduction of CAN XL as this databittiming
validation will be reused later on.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
---
 drivers/net/can/dev/netlink.c | 60 ++++++++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 18 deletions(-)

diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index 1367ebe5db8fd6fcac49d3a1f59d44b61847128f..f7b12057bc9c6c286aa0c4341d565a497254296d 100644
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c
@@ -99,10 +99,48 @@ static int can_validate_tdc(struct nlattr *data_tdc,
 	return 0;
 }
 
+static int can_validate_databittiming(struct nlattr *data[],
+				      struct netlink_ext_ack *extack,
+				      int ifla_can_data_bittiming, u32 flags)
+{
+	struct nlattr *data_tdc;
+	u32 tdc_flags;
+	bool is_on;
+	int err;
+
+	if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
+		data_tdc = data[IFLA_CAN_TDC];
+		tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
+		is_on = flags & CAN_CTRLMODE_FD;
+	} else {
+		WARN_ON(1); /* Place holder for CAN XL */
+	}
+
+	if (is_on) {
+		if (!data[IFLA_CAN_BITTIMING] || !data[ifla_can_data_bittiming])
+			return -EOPNOTSUPP;
+	}
+
+	if (data[ifla_can_data_bittiming] || data_tdc) {
+		if (!is_on)
+			return -EOPNOTSUPP;
+	}
+
+	err = can_validate_bittiming(data, extack, ifla_can_data_bittiming);
+	if (err)
+		return err;
+
+	err = can_validate_tdc(data_tdc, extack, tdc_flags);
+	if (err)
+		return err;
+
+	return 0;
+}
+
 static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
-	bool is_can_fd = false;
+	u32 flags = 0;
 	int err;
 
 	/* Make sure that valid CAN FD configurations always consist of
@@ -118,29 +156,15 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm = nla_data(data[IFLA_CAN_CTRLMODE]);
 
-		is_can_fd = cm->flags & cm->mask & CAN_CTRLMODE_FD;
-
-		err = can_validate_tdc(data[IFLA_CAN_TDC], extack,
-				       cm->flags & CAN_CTRLMODE_FD_TDC_MASK);
-		if (err)
-			return err;
+		flags = cm->flags & cm->mask;
 	}
 
 	err = can_validate_bittiming(data, extack, IFLA_CAN_BITTIMING);
 	if (err)
 		return err;
 
-	if (is_can_fd) {
-		if (!data[IFLA_CAN_BITTIMING] || !data[IFLA_CAN_DATA_BITTIMING])
-			return -EOPNOTSUPP;
-	}
-
-	if (data[IFLA_CAN_DATA_BITTIMING] || data[IFLA_CAN_TDC]) {
-		if (!is_can_fd)
-			return -EOPNOTSUPP;
-	}
-
-	err = can_validate_bittiming(data, extack, IFLA_CAN_DATA_BITTIMING);
+	err = can_validate_databittiming(data, extack,
+					 IFLA_CAN_DATA_BITTIMING, flags);
 	if (err)
 		return err;
 

-- 
2.49.1

Hi Vincent,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3]

url:    https://github.com/intel-lab-lkp/linux/commits/Vincent-Mailhol/can-dev-move-struct-data_bittiming_params-to-linux-can-bittiming-h/20250903-170807
base:   2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
patch link:    https://lore.kernel.org/r/20250903-canxl-netlink-prep-v1-6-904bd6037cd9%40kernel.org
patch subject: [PATCH 06/21] can: netlink: add can_validate_databittiming()
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509050259.NjPdQyAD-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/net/can/dev/netlink.c:111:6: warning: variable 'is_on' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
     111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/can/dev/netlink.c:119:6: note: uninitialized use occurs here
     119 |         if (is_on) {
         |             ^~~~~
   drivers/net/can/dev/netlink.c:111:2: note: remove the 'if' if its condition is always true
     111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     112 |                 data_tdc = data[IFLA_CAN_TDC];
     113 |                 tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
     114 |                 is_on = flags & CAN_CTRLMODE_FD;
     115 |         } else {
         |           ~~~~~~
     116 |                 WARN_ON(1); /* Place holder for CAN XL */
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     117 |         }
         |         ~
   drivers/net/can/dev/netlink.c:108:12: note: initialize the variable 'is_on' to silence this warning
     108 |         bool is_on;
         |                   ^
         |                    = 0
   1 warning generated.


vim +111 drivers/net/can/dev/netlink.c

   101	
   102	static int can_validate_databittiming(struct nlattr *data[],
   103					      struct netlink_ext_ack *extack,
   104					      int ifla_can_data_bittiming, u32 flags)
   105	{
   106		struct nlattr *data_tdc;
   107		u32 tdc_flags;
   108		bool is_on;
   109		int err;
   110	
 > 111		if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
   112			data_tdc = data[IFLA_CAN_TDC];
   113			tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
   114			is_on = flags & CAN_CTRLMODE_FD;
   115		} else {
   116			WARN_ON(1); /* Place holder for CAN XL */
   117		}
   118	
   119		if (is_on) {
   120			if (!data[IFLA_CAN_BITTIMING] || !data[ifla_can_data_bittiming])
   121				return -EOPNOTSUPP;
   122		}
   123	
   124		if (data[ifla_can_data_bittiming] || data_tdc) {
   125			if (!is_on)
   126				return -EOPNOTSUPP;
   127		}
   128	
   129		err = can_validate_bittiming(data, extack, ifla_can_data_bittiming);
   130		if (err)
   131			return err;
   132	
   133		err = can_validate_tdc(data_tdc, extack, tdc_flags);
   134		if (err)
   135			return err;
   136	
   137		return 0;
   138	}
   139	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

On 05/09/2025 at 03:46, kernel test robot wrote:
> Hi Vincent,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3]

OK. I will silence it in v2, but I don't think this is anyhow problematic.

> url:    https://github.com/intel-lab-lkp/linux/commits/Vincent-Mailhol/can-dev-move-struct-data_bittiming_params-to-linux-can-bittiming-h/20250903-170807
> base:   2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
> patch link:    https://lore.kernel.org/r/20250903-canxl-netlink-prep-v1-6-904bd6037cd9%40kernel.org
> patch subject: [PATCH 06/21] can: netlink: add can_validate_databittiming()
> config: x86_64-kexec (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/config)
> compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250905/202509050259.NjPdQyAD-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202509050259.NjPdQyAD-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/net/can/dev/netlink.c:111:6: warning: variable 'is_on' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>      111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
>          |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/net/can/dev/netlink.c:119:6: note: uninitialized use occurs here
>      119 |         if (is_on) {
>          |             ^~~~~
>    drivers/net/can/dev/netlink.c:111:2: note: remove the 'if' if its condition is always true

That's it. This if condition is always true at the moment because all the
callers specify ifla_can_data_bittiming as IFLA_CAN_DATA_BITTIMING. But I do not
want to remove the else branch because is serves to show to the reader what is
coming up next and help to understand the refactor logic.
>      111 |         if (ifla_can_data_bittiming == IFLA_CAN_DATA_BITTIMING) {
>          |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>      112 |                 data_tdc = data[IFLA_CAN_TDC];
>      113 |                 tdc_flags = flags & CAN_CTRLMODE_FD_TDC_MASK;
>      114 |                 is_on = flags & CAN_CTRLMODE_FD;
>      115 |         } else {
>          |           ~~~~~~
>      116 |                 WARN_ON(1); /* Place holder for CAN XL */
>          |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The WARN_ON(1) was to point out that the else branch should never be reached.

I will change this to:

	return -EOPNOTSUPP; /* Place holder for CAN XL */

in v2. This will serve the same purpose as the current WARN_ON(1) but will
suppress the warning.

I will do the exact same on patches 11/21 and 18/21 on which the kernel test
robot also sent a similar report.


Yours sincerely,
Vincent Mailhol