netdev - [PATCH v4 4/7] can: dev: add can_tdc_get_relative

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210814091750.73931-5-mailhol.vincent@wanadoo.fr>
Date:   Sat, 14 Aug 2021 18:17:47 +0900
From:   Vincent Mailhol <mailhol.vincent@...adoo.fr>
To:     Marc Kleine-Budde <mkl@...gutronix.de>, linux-can@...r.kernel.org
Cc:     Stefan Mätje <Stefan.Maetje@....eu>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>
Subject: [PATCH v4 4/7] can: dev: add can_tdc_get_relative_tdco() helper function

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

Consequently:
| relative TDCO = absolute TDCO - SP

The function can_tdc_get_relative_tdco() allow to retrieve this
relative TDCO value.

CC: Stefan Mätje <Stefan.Maetje@....eu>
Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
---
 include/linux/can/dev.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 0be982fd22fb..fa75e29182a3 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -93,6 +93,35 @@ static inline bool can_tdc_is_enabled(const struct can_priv *priv)
 	return !!(priv->ctrlmode & CAN_CTRLMODE_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->data_bittiming;
+	s32 sample_point_in_tc =  (CAN_SYNC_SEG + dbt->prop_seg +
+				   dbt->phase_seg1) * dbt->brp;
+
+	return (s32)priv->tdc.tdco - sample_point_in_tc;
+}
+
 /* helper to define static CAN controller features at device creation time */
 static inline void can_set_static_ctrlmode(struct net_device *dev,
 					   u32 static_mode)
-- 
2.31.1