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can: dev: add a helper function to calculate the duration of one bit

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Rename macro CAN_CALC_SYNC_SEG to CAN_SYNC_SEG and make it available
through include/linux/can/dev.h

Add an helper function can_bit_time() which returns the duration (in
time quanta) of one CAN bit.

Rationale for this patch: the sync segment and the bit time are two
concepts which are defined in the CAN ISO standard. Device drivers for
CAN might need those.

Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
additional information.

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/r/20201002154219.4887-6-mailhol.vincent@wanadoo.fr
[mkl: Let can_bit_time() return an unsinged int, make argument const]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Vincent Mailhol
2020-10-03 00:41:49 +09:00
committed by Marc Kleine-Budde
parent f55a52bb2c
commit 1c47fa6b31
2 changed files with 21 additions and 7 deletions
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15
include/linux/can/dev.h
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@@ -82,6 +82,21 @@ struct can_priv {
#endif
};
#define CAN_SYNC_SEG 1
/*
* can_bit_time() - Duration of one bit
*
* Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
* additional information.
*
* Return: the number of time quanta in one bit.
*/
static inline unsigned int can_bit_time(const struct can_bittiming *bt)
{
return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
}
/*
* get_can_dlc(value) - helper macro to cast a given data length code (dlc)
* to u8 and ensure the dlc value to be max. 8 bytes.