linux-kernel - [PATCH 02/21] can: dev: make can_get_relative_tdco() FD agnostic and move it to bittiming.h

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Message-Id: <20250903-canxl-netlink-prep-v1-2-904bd6037cd9@kernel.org>
Date: Wed, 03 Sep 2025 17:50:01 +0900
From: Vincent Mailhol <mailhol@...nel.org>
To: Marc Kleine-Budde <mkl@...gutronix.de>, 
 Oliver Hartkopp <socketcan@...tkopp.net>
Cc: Vincent Mailhol <mailhol@...nel.org>, 
 Stéphane Grosjean <stephane.grosjean@...-networks.com>, 
 Robert Nawrath <mbro1689@...il.com>, Minh Le <minh.le.aj@...esas.com>, 
 Duy Nguyen <duy.nguyen.rh@...esas.com>, linux-can@...r.kernel.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH 02/21] can: dev: make can_get_relative_tdco() FD agnostic
 and move it to bittiming.h

can_get_relative_tdco() needs to access can_priv->fd making it
specific to CAN FD. Change the function parameter from struct can_priv
to struct data_bittiming_params. This way, the function becomes CAN FD
agnostic and can be reused later on for the CAN XL TDC.

Now that we dropped the dependency on struct can_priv, also move
can_get_relative_tdco() back to bittiming.h where it was meant to
belong to.

Signed-off-by: Vincent Mailhol <mailhol@...nel.org>
---
Changelog:

  RFC -> v1:

   - Just pass the IFLA index instead of passing each argument
     individually. Instead, derive these as local variables depending
     on whethe the IFLA index is IFLA_CAN_TDC or IFLA_CAN_XL_TDC.
---
 include/linux/can/bittiming.h | 29 +++++++++++++++++++++++++++++
 include/linux/can/dev.h       | 29 -----------------------------
 2 files changed, 29 insertions(+), 29 deletions(-)

diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h
index 6572ec1712ca2df8db7fe1453ae5a4d5699712b1..4d5f7794194ab13641c7854c2d66625c4e942f6c 100644
--- a/include/linux/can/bittiming.h
+++ b/include/linux/can/bittiming.h
@@ -160,6 +160,35 @@ int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
 		      const unsigned int bitrate_const_cnt,
 		      struct netlink_ext_ack *extack);
 
+/*
+ * can_get_relative_tdco() - TDCO relative to the sample point
+ *
+ * struct can_tdc::tdco represents the absolute offset from TDCV. Some
+ * controllers use instead an offset relative to the Sample Point (SP)
+ * such that:
+ *
+ * SSP = TDCV + absolute TDCO
+ *     = TDCV + SP + relative TDCO
+ *
+ * -+----------- one bit ----------+-- TX pin
+ *  |<--- Sample Point --->|
+ *
+ *                         --+----------- one bit ----------+-- RX pin
+ *  |<-------- TDCV -------->|
+ *                           |<------------------------>| absolute TDCO
+ *                           |<--- Sample Point --->|
+ *                           |                      |<->| relative TDCO
+ *  |<------------- Secondary Sample Point ------------>|
+ */
+static inline s32 can_get_relative_tdco(const struct data_bittiming_params *dbt_params)
+{
+	const struct can_bittiming *dbt = &dbt_params->data_bittiming;
+	s32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
+				  dbt->phase_seg1) * dbt->brp;
+
+	return (s32)dbt_params->tdc.tdco - sample_point_in_tc;
+}
+
 /*
  * can_bit_time() - Duration of one bit
  *
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 76022f48a97673d81676c39c697eadc6d7063ff7..55aaadaacf68f940fa1b71f7c438e68b84080292 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -85,35 +85,6 @@ static inline bool can_fd_tdc_is_enabled(const struct can_priv *priv)
 	return !!(priv->ctrlmode & CAN_CTRLMODE_FD_TDC_MASK);
 }
 
-/*
- * can_get_relative_tdco() - TDCO relative to the sample point
- *
- * struct can_tdc::tdco represents the absolute offset from TDCV. Some
- * controllers use instead an offset relative to the Sample Point (SP)
- * such that:
- *
- * SSP = TDCV + absolute TDCO
- *     = TDCV + SP + relative TDCO
- *
- * -+----------- one bit ----------+-- TX pin
- *  |<--- Sample Point --->|
- *
- *                         --+----------- one bit ----------+-- RX pin
- *  |<-------- TDCV -------->|
- *                           |<------------------------>| absolute TDCO
- *                           |<--- Sample Point --->|
- *                           |                      |<->| relative TDCO
- *  |<------------- Secondary Sample Point ------------>|
- */
-static inline s32 can_get_relative_tdco(const struct can_priv *priv)
-{
-	const struct can_bittiming *dbt = &priv->fd.data_bittiming;
-	s32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
-				  dbt->phase_seg1) * dbt->brp;
-
-	return (s32)priv->fd.tdc.tdco - sample_point_in_tc;
-}
-
 /* helper to define static CAN controller features at device creation time */
 static inline int __must_check can_set_static_ctrlmode(struct net_device *dev,
 						       u32 static_mode)

-- 
2.49.1