On 26.07.2022 23:02:08, Dario Binacchi wrote:
> With this series I try to finish the task, started with the series [1],
> of completely removing the dependency of the slcan driver from the
> userspace slcand/slcan_attach applications.
>
> The series also contains patches that remove the legacy stuff (slcan_devs,
> SLCAN_MAGIC, ...) and do some module cleanup.
>
> The series has been created on top of the patches:
>
> can: slcan: convert comments to network style comments
> can: slcan: slcan_init() convert printk(LEVEL ...) to pr_level()
> can: slcan: fix whitespace issues
> can: slcan: convert comparison to NULL into !val
> can: slcan: clean up if/else
> can: slcan: use scnprintf() as a hardening measure
> can: slcan: do not report txerr and rxerr during bus-off
> can: slcan: do not sleep with a spin lock held
>
> applied to linux-next.
>
> [1] https://lore.kernel.org/all/[email protected]/
>
> Changes in v3:
> - Update the commit message.
> - Use 1 space in front of the =.
> - Put the series as RFC again.

No need to change the series to RFC again :)

> - Pick up the patch "can: slcan: use KBUILD_MODNAME and define pr_fmt to replace hardcoded names".
> - Add the patch "ethtool: add support to get/set CAN bit time register"
> to the series.
> - Add the patch "can: slcan: add support to set bit time register (btr)"
> to the series.
> - Replace the link https://marc.info/?l=linux-can&m=165806705927851&w=2 with
> https://lore.kernel.org/all/[email protected].
> - Add the `Suggested-by' tag.

Please post a v4 with both BTR patches dropped and add Max Staudt's
Reviewed-by to patch 3.

Marc

--
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Embedded Linux | https://www.pengutronix.de |
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2022-07-27 19:09:29

by Marc Kleine-Budde

[permalink] [raw]

Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

On 27.07.2022 19:28:39, Max Staudt wrote:
> On Wed, 27 Jul 2022 13:30:54 +0200
> Marc Kleine-Budde <[email protected]> wrote:
>
> > As far as I understand, setting the btr is an alternative way to set the
> > bitrate, right? I don't like the idea of poking arbitrary values into a
> > hardware from user space.
>
> I agree with Marc here.
>
> This is a modification across the whole stack, specific to a single
> device, when there are ways around.
>
> If I understand correctly, the CAN232 "S" command sets one of the fixed
> bitrates, whereas "s" sets the two BTR registers. Now the question is,
> what do BTR0/BTR1 mean, and what are they? If they are merely a divider
> in a CAN controller's master clock, like in ELM327, then you could
>
> a) Calculate the BTR values from the bitrate userspace requests, or

Most of the other CAN drivers write the BTR values into the register of
the hardware. How are these BTR values transported into the driver?

There are 2 ways:

1) - user space configures a bitrate
- the kernel calculates with the "struct can_bittiming_const" [1] given
by driver and the CAN clock rate the low level timing parameters.

[1] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L47

2) - user space configures low level bit timing parameter
(Sample point in one-tenth of a percent, Time quanta (TQ) in
nanoseconds, Propagation segment in TQs, Phase buffer segment 1 in
TQs, Phase buffer segment 2 in TQs, Synchronisation jump width in
TQs)
- the kernel calculates the Bit-rate prescaler from the given TQ and
CAN clock rate

Both ways result in a fully calculated "struct can_bittiming" [2]. The
driver translates this into the hardware specific BTR values and writes
the into the registers.

If you know the CAN clock and the bit timing const parameters of the
slcan's BTR register you can make use of the automatic BTR calculation,
too. Maybe the framework needs some tweaking if the driver supports both
fixed CAN bit rate _and_ "struct can_bittiming_const".

[2] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L31

> b) pre-calculate a huge table of possible bitrates and present them
> all to userspace. Sounds horrible, but that's what I did in can327,
> haha. Maybe I should have reigned them in a little, to the most
> useful values.

If your adapter only supports fixed values, then that's the only way to
go.

> c) just limit the bitrates to whatever seems most useful (like the
> "S" command's table), and let users complain if they really need
> something else. In the meantime, they are still free to slcand or
> minicom to their heart's content before attaching slcan, thanks to
> your backwards compatibility efforts.

In the early stages of the non-mainline CAN framework we had tables for
BTR values for some fixed bit rates, but that turned out to be not
scaleable.

> In short, to me, this isn't a deal breaker for your patch series.

Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

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2022-07-27 19:22:21

On 27.07.2022 22:12:13, Oliver Hartkopp wrote:
>
>
> On 27.07.22 20:24, Marc Kleine-Budde wrote:
> > On 27.07.2022 19:28:39, Max Staudt wrote:
> > > On Wed, 27 Jul 2022 13:30:54 +0200
> > > Marc Kleine-Budde <[email protected]> wrote:
> > >
> > > > As far as I understand, setting the btr is an alternative way to set the
> > > > bitrate, right? I don't like the idea of poking arbitrary values into a
> > > > hardware from user space.
> > >
> > > I agree with Marc here.
> > >
> > > This is a modification across the whole stack, specific to a single
> > > device, when there are ways around.
> > >
> > > If I understand correctly, the CAN232 "S" command sets one of the fixed
> > > bitrates, whereas "s" sets the two BTR registers. Now the question is,
> > > what do BTR0/BTR1 mean, and what are they? If they are merely a divider
> > > in a CAN controller's master clock, like in ELM327, then you could
> > >
> > > a) Calculate the BTR values from the bitrate userspace requests, or
> >
> > Most of the other CAN drivers write the BTR values into the register of
> > the hardware. How are these BTR values transported into the driver?
> >
> > There are 2 ways:
> >
> > 1) - user space configures a bitrate
> > - the kernel calculates with the "struct can_bittiming_const" [1] given
> > by driver and the CAN clock rate the low level timing parameters.
> >
> > [1] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L47
> >
> > 2) - user space configures low level bit timing parameter
> > (Sample point in one-tenth of a percent, Time quanta (TQ) in
> > nanoseconds, Propagation segment in TQs, Phase buffer segment 1 in
> > TQs, Phase buffer segment 2 in TQs, Synchronisation jump width in
> > TQs)
> > - the kernel calculates the Bit-rate prescaler from the given TQ and
> > CAN clock rate
> >
> > Both ways result in a fully calculated "struct can_bittiming" [2]. The
> > driver translates this into the hardware specific BTR values and writes
> > the into the registers.
> >
> > If you know the CAN clock and the bit timing const parameters of the
> > slcan's BTR register you can make use of the automatic BTR calculation,
> > too. Maybe the framework needs some tweaking if the driver supports both
> > fixed CAN bit rate _and_ "struct can_bittiming_const".
> >
> > [2] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L31
> >
> > > b) pre-calculate a huge table of possible bitrates and present them
> > > all to userspace. Sounds horrible, but that's what I did in can327,
> > > haha. Maybe I should have reigned them in a little, to the most
> > > useful values.
> >
> > If your adapter only supports fixed values, then that's the only way to
> > go.
> >
> > > c) just limit the bitrates to whatever seems most useful (like the
> > > "S" command's table), and let users complain if they really need
> > > something else. In the meantime, they are still free to slcand or
> > > minicom to their heart's content before attaching slcan, thanks to
> > > your backwards compatibility efforts.
> >
> > In the early stages of the non-mainline CAN framework we had tables for
> > BTR values for some fixed bit rates, but that turned out to be not
> > scaleable.
>
> The Microchip CAN BUS Analyzer Tool is another example for fixed bitrates:
>
> https://elixir.bootlin.com/linux/v5.18.14/source/drivers/net/can/usb/mcba_usb.c#L156
>
> So this might be the way to go here too ...

The slcan driver already supports fixed bitrates. This discussion is
about setting the BTR registers in one way or another.

Marc

--
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Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
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2022-07-28 07:42:28

by Dario Binacchi

[permalink] [raw]

Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

Hello Marc,

On Wed, Jul 27, 2022 at 8:24 PM Marc Kleine-Budde <[email protected]> wrote:
>
> On 27.07.2022 19:28:39, Max Staudt wrote:
> > On Wed, 27 Jul 2022 13:30:54 +0200
> > Marc Kleine-Budde <[email protected]> wrote:
> >
> > > As far as I understand, setting the btr is an alternative way to set the
> > > bitrate, right? I don't like the idea of poking arbitrary values into a
> > > hardware from user space.
> >
> > I agree with Marc here.
> >
> > This is a modification across the whole stack, specific to a single
> > device, when there are ways around.
> >
> > If I understand correctly, the CAN232 "S" command sets one of the fixed
> > bitrates, whereas "s" sets the two BTR registers. Now the question is,
> > what do BTR0/BTR1 mean, and what are they? If they are merely a divider
> > in a CAN controller's master clock, like in ELM327, then you could
> >
> > a) Calculate the BTR values from the bitrate userspace requests, or
>
> Most of the other CAN drivers write the BTR values into the register of
> the hardware. How are these BTR values transported into the driver?
>
> There are 2 ways:
>
> 1) - user space configures a bitrate
> - the kernel calculates with the "struct can_bittiming_const" [1] given
> by driver and the CAN clock rate the low level timing parameters.
>
> [1] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L47
>
> 2) - user space configures low level bit timing parameter
> (Sample point in one-tenth of a percent, Time quanta (TQ) in
> nanoseconds, Propagation segment in TQs, Phase buffer segment 1 in
> TQs, Phase buffer segment 2 in TQs, Synchronisation jump width in
> TQs)
> - the kernel calculates the Bit-rate prescaler from the given TQ and
> CAN clock rate
>
> Both ways result in a fully calculated "struct can_bittiming" [2]. The
> driver translates this into the hardware specific BTR values and writes
> the into the registers.
>
> If you know the CAN clock and the bit timing const parameters of the
> slcan's BTR register you can make use of the automatic BTR calculation,
> too. Maybe the framework needs some tweaking if the driver supports both
> fixed CAN bit rate _and_ "struct can_bittiming_const".

Does it make sense to use the device tree to provide the driver with those
parameters required for the automatic calculation of the BTR (clock rate,
struct can_bittiming_const, ...) that depend on the connected controller? In
this way the solution should be generic and therefore scalable. I think we
should also add some properties to map the calculated BTR value on the
physical register of the controller.

Or, use the device tree to extend the bittates supported by the controller
to the fixed ones (struct can_priv::bitrate_const)?

Thanks and regards,
Dario

>
> [2] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L31
>
> > b) pre-calculate a huge table of possible bitrates and present them
> > all to userspace. Sounds horrible, but that's what I did in can327,
> > haha. Maybe I should have reigned them in a little, to the most
> > useful values.
>
> If your adapter only supports fixed values, then that's the only way to
> go.
>
> > c) just limit the bitrates to whatever seems most useful (like the
> > "S" command's table), and let users complain if they really need
> > something else. In the meantime, they are still free to slcand or
> > minicom to their heart's content before attaching slcan, thanks to
> > your backwards compatibility efforts.
>
> In the early stages of the non-mainline CAN framework we had tables for
> BTR values for some fixed bit rates, but that turned out to be not
> scaleable.
>
> > In short, to me, this isn't a deal breaker for your patch series.
>
> Marc
>
> --
> Pengutronix e.K. | Marc Kleine-Budde |
> Embedded Linux | https://www.pengutronix.de |
> Vertretung West/Dortmund | Phone: +49-231-2826-924 |
> Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

--

Dario Binacchi

Embedded Linux Developer

[email protected]

__________________________________

Amarula Solutions SRL

Via Le Canevare 30, 31100 Treviso, Veneto, IT

T. +39 042 243 5310
[email protected]

http://www.amarulasolutions.com

2022-07-28 09:20:41

by Marc Kleine-Budde

[permalink] [raw]

Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

On 28.07.2022 09:36:21, Dario Binacchi wrote:
> > Most of the other CAN drivers write the BTR values into the register of
> > the hardware. How are these BTR values transported into the driver?
> >
> > There are 2 ways:
> >
> > 1) - user space configures a bitrate
> > - the kernel calculates with the "struct can_bittiming_const" [1] given
> > by driver and the CAN clock rate the low level timing parameters.
> >
> > [1] https://elixir.bootlin.com/linux/v5.18/source/include/uapi/linux/can/netlink.h#L47
> >
> > 2) - user space configures low level bit timing parameter
> > (Sample point in one-tenth of a percent, Time quanta (TQ) in
> > nanoseconds, Propagation segment in TQs, Phase buffer segment 1 in
> > TQs, Phase buffer segment 2 in TQs, Synchronisation jump width in
> > TQs)
> > - the kernel calculates the Bit-rate prescaler from the given TQ and
> > CAN clock rate
> >
> > Both ways result in a fully calculated "struct can_bittiming" [2]. The
> > driver translates this into the hardware specific BTR values and writes
> > the into the registers.
> >
> > If you know the CAN clock and the bit timing const parameters of the
> > slcan's BTR register you can make use of the automatic BTR calculation,
> > too. Maybe the framework needs some tweaking if the driver supports both
> > fixed CAN bit rate _and_ "struct can_bittiming_const".
>
> Does it make sense to use the device tree

The driver doesn't support DT and DT only works for static serial
interfaces.

> to provide the driver with those
> parameters required for the automatic calculation of the BTR (clock rate,
> struct can_bittiming_const, ...) that depend on the connected
> controller?

The device tree usually says it's a CAN controller compatible to X and
the following clock(s) are connected. The driver for CAN controller X
knows the bit timing const. Some USB CAN drivers query the bit timing
const from the USB device.

> In this way the solution should be generic and therefore scalable. I
> think we should also add some properties to map the calculated BTR
> value on the physical register of the controller.

The driver knows how to map the "struct can_bittiming" to the BTR
register values of the hardware.

What does the serial protocol say to the BTR values? Are these standard
SJA1000 layout with 8 MHz CAN clock or are those adapter specific?

> Or, use the device tree to extend the bittates supported by the controller
> to the fixed ones (struct can_priv::bitrate_const)?

The serial protocol defines fixed bit rates, no need to describe them in
the DT:

| 0 10 Kbit/s
| 1 20 Kbit/s
| 2 50 Kbit/s
| 3 100 Kbit/s
| 4 125 Kbit/s
| 5 250 Kbit/s
| 6 500 Kbit/s
| 7 800 Kbit/s
| 8 1000 Kbit/s

Are there more bit rates?

regards,
Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

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2022-07-28 10:58:36

On 29.07.2022 08:52:07, Dario Binacchi wrote:
> Hello Marc and Max,
>
> On Thu, Jul 28, 2022 at 12:57 PM Max Staudt <[email protected]> wrote:
> >
> > On Thu, 28 Jul 2022 12:50:49 +0200
> > Marc Kleine-Budde <[email protected]> wrote:
> >
> > > On 28.07.2022 12:23:04, Dario Binacchi wrote:
> > > > > > Does it make sense to use the device tree
> > > > >
> > > > > The driver doesn't support DT and DT only works for static serial
> > > > > interfaces.
> > >
> > > Have you seen my remarks about Device Tree?
> >
> > Dario, there seems to be a misunderstanding about the Device Tree.
> >
> > It is used *only* for hardware that is permanently attached, present at
> > boot, and forever after. Not for dyamically added stuff, and definitely
> > not for ldiscs that have to be attached manually by the user.
> >
> >
> > The only exception to this is if you have an embedded device with an
> > slcan adapter permanently attached to one of its UARTs. Then you can
> > use the serdev ldisc adapter to attach the ldisc automatically at boot.
>
> It is evident that I am lacking some skills (I will try to fix it :)).

We're all here to learn something!

> I think it is equally clear that it is not worth going down this path.

If you have a static attached serial devices serdev is the way to go.
But slcan has so many drawbacks compared to "real" CAN adapters that I
hope the no one uses them in such a scenario.

> > If you are actively developing for such a use case, please let us know,
> > so we know what you're after and can help you better :)
>
> I don't have a use case, other than to try, if possible, to make the driver
> autonomous from slcand / slcan_attach for the CAN bus setup.

From my point of view your job is done!

> Returning to Marc's previous analysis:
> "... Some USB CAN drivers query the bit timing const from the USB device."
>
> Can we think of taking the gs_usb driver as inspiration for getting/setting the
> bit timings?
>
> https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/gs_usb.c#L951
> https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/gs_usb.c#L510
>
> and, as done with patches:
>
> can: slcan: extend the protocol with CAN state info
> can: slcan: extend the protocol with error info

You can define a way to query bit timing constants and CAN clock rate,
but you have to get this into the "official" firmware. You have to roll
out a firmware update to all devices. What about non official firmware?

> further extend the protocol to get/set the bit timing from / to the adapter ?
> In the case of non-standard bit rates, the driver would try, depending on the
> firmware of the adapter, to calculate and set the bit timings autonomously.

If an adapter follows 100% the official firmware doc the BTR registers
are interpreted as SJA1000 with 8 MHz CAN clock.

See

| https://lore.kernel.org/all/[email protected]

where I compare the 125 Kbit/s BTR config of the documentation with the
bit timing calculated by the kernel algorithm.

regards,
Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
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2022-07-31 16:00:46

by Dario Binacchi

[permalink] [raw]

Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

Hi Marc,

On Fri, Jul 29, 2022 at 9:33 AM Marc Kleine-Budde <[email protected]> wrote:
>
> On 29.07.2022 08:52:07, Dario Binacchi wrote:
> > Hello Marc and Max,
> >
> > On Thu, Jul 28, 2022 at 12:57 PM Max Staudt <[email protected]> wrote:
> > >
> > > On Thu, 28 Jul 2022 12:50:49 +0200
> > > Marc Kleine-Budde <[email protected]> wrote:
> > >
> > > > On 28.07.2022 12:23:04, Dario Binacchi wrote:
> > > > > > > Does it make sense to use the device tree
> > > > > >
> > > > > > The driver doesn't support DT and DT only works for static serial
> > > > > > interfaces.
> > > >
> > > > Have you seen my remarks about Device Tree?
> > >
> > > Dario, there seems to be a misunderstanding about the Device Tree.
> > >
> > > It is used *only* for hardware that is permanently attached, present at
> > > boot, and forever after. Not for dyamically added stuff, and definitely
> > > not for ldiscs that have to be attached manually by the user.
> > >
> > >
> > > The only exception to this is if you have an embedded device with an
> > > slcan adapter permanently attached to one of its UARTs. Then you can
> > > use the serdev ldisc adapter to attach the ldisc automatically at boot.
> >
> > It is evident that I am lacking some skills (I will try to fix it :)).
>
> We're all here to learn something!
>
> > I think it is equally clear that it is not worth going down this path.
>
> If you have a static attached serial devices serdev is the way to go.
> But slcan has so many drawbacks compared to "real" CAN adapters that I
> hope the no one uses them in such a scenario.
>
> > > If you are actively developing for such a use case, please let us know,
> > > so we know what you're after and can help you better :)
> >
> > I don't have a use case, other than to try, if possible, to make the driver
> > autonomous from slcand / slcan_attach for the CAN bus setup.
>
> From my point of view your job is done!

Ok.

>
> > Returning to Marc's previous analysis:
> > "... Some USB CAN drivers query the bit timing const from the USB device."
> >
> > Can we think of taking the gs_usb driver as inspiration for getting/setting the
> > bit timings?
> >
> > https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/gs_usb.c#L951
> > https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/gs_usb.c#L510
> >
> > and, as done with patches:
> >
> > can: slcan: extend the protocol with CAN state info
> > can: slcan: extend the protocol with error info
>
> You can define a way to query bit timing constants and CAN clock rate,
> but you have to get this into the "official" firmware. You have to roll
> out a firmware update to all devices. What about non official firmware?
>
> > further extend the protocol to get/set the bit timing from / to the adapter ?
> > In the case of non-standard bit rates, the driver would try, depending on the
> > firmware of the adapter, to calculate and set the bit timings autonomously.
>
> If an adapter follows 100% the official firmware doc the BTR registers
> are interpreted as SJA1000 with 8 MHz CAN clock.

I checked the sources and documentation of the usb adapter I used (i.
e. Https://www.fischl.de/usbtin/):
...
sxxyyzz[CR] Set can bitrate registers of MCP2515. You
can set non-standard baudrates which are not supported by the "Sx"
command.
xx: CNF1 as hexadecimal value (00-FF)
yy: CNF2 as hexadecimal value (00-FF)
zz: CNF3 as hexadecimal value
...

Different from what is reported by can232_ver3_Manual.pdf :

sxxyy[CR] Setup with BTR0/BTR1 CAN bit-rates where xx and yy is a hex
value. This command is only active if the CAN

And here is the type of control carried out by the slcan_attach for
the btr parameter:
https://github.com/linux-can/can-utils/blob/master/slcan_attach.c#L144
When I would have expected a different check (i. e. if (strlen(btr) > 4).
Therefore it is possible that each adapter uses these bytes in its own
way as well as
in the content and also in the number of bytes.

Thanks and regards,
Dario

>
> See
>
> | https://lore.kernel.org/all/[email protected]
>
> where I compare the 125 Kbit/s BTR config of the documentation with the
> bit timing calculated by the kernel algorithm.
>
> regards,
> Marc
>
> --
> Pengutronix e.K. | Marc Kleine-Budde |
> Embedded Linux | https://www.pengutronix.de |
> Vertretung West/Dortmund | Phone: +49-231-2826-924 |
> Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |

--

Dario Binacchi

Embedded Linux Developer

[email protected]

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Amarula Solutions SRL

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2022-07-31 18:59:42

by Marc Kleine-Budde

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Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

On 31.07.2022 17:54:01, Dario Binacchi wrote:
> > If an adapter follows 100% the official firmware doc the BTR registers
> > are interpreted as SJA1000 with 8 MHz CAN clock.
>
> I checked the sources and documentation of the usb adapter I used (i.
> e. Https://www.fischl.de/usbtin/):
> ...
> sxxyyzz[CR] Set can bitrate registers of MCP2515. You
> can set non-standard baudrates which are not supported by the "Sx"
> command.

I hope the effective clock speed is documented somewhere, as you need
this information to set the registers.

> xx: CNF1 as hexadecimal value (00-FF)
> yy: CNF2 as hexadecimal value (00-FF)
> zz: CNF3 as hexadecimal value
> ...
>
> Different from what is reported by can232_ver3_Manual.pdf :
>
> sxxyy[CR] Setup with BTR0/BTR1 CAN bit-rates where xx and yy is a hex
> value. This command is only active if the CAN
>
> And here is the type of control carried out by the slcan_attach for
> the btr parameter:
> https://github.com/linux-can/can-utils/blob/master/slcan_attach.c#L144
> When I would have expected a different check (i. e. if (strlen(btr) > 4).
> Therefore it is possible that each adapter uses these bytes in its own
> way as well as
> in the content and also in the number of bytes.

I expected something like that.

regards,
Marc

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