netdev - Re: CAN-FD Transceiver Limitations

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Message-ID: <6f9f7a0b-ff9d-15bd-47be-012986a452c3@pengutronix.de>
Date:   Mon, 10 Jul 2017 16:58:28 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Andrew Lunn <andrew@...n.ch>, Franklin S Cooper Jr <fcooper@...com>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        wg@...ndegger.com
Subject: Re: CAN-FD Transceiver Limitations

On 06/29/2017 05:41 PM, Andrew Lunn wrote:
>> Transceivers for CAN are not apart of any model. Traditional CAN didn't
>> have a problem because all transceivers from my understanding supported
>> the maximum speed of 1 Mbps defined by the spec. However, with the
>> introduction of CAN Flexible Datarate mode it seems that for
>> transceivers that supported CAN-FD the maximum supported speeds vary.
> 
> So transceivers are dumb devices, nothing to configure, so no need to
> have a driver for them.

Yes and no.

CAN transceivers are usually quite dumb, but most of them have some sort
of "enable" pin. This pin is currently modelled as a regulator. Which
fits nicely, as there dual transceivers with only one enable pin.

However there are more complicated transceivers with two pins, that
implement a state machine, where you can query the chip for various
error conditions and can configure remote wakeup, etc... So in the
future a proper driver might be implemented.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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