serial tty name

[Richard Zhao]

How to map different uart port to ttymxc0 (take imx for example)?

In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.

But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.

Is there a way to fix it?


Thanks
Richard

[Igor Grinberg]

Hi Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

As for fix in userspace, you can spawn getty on every ttymxc*,
so you will get it always.

Another (userspace) fix would be:
Instead of getty, add a script (say getty.sh) which will do something like:
-----------
CONSOLE=`cat /proc/cmdline | tr " " "\n" | grep console= | tr "=" " " | tr "," " "`
TTY=`echo $CONSOLE | cut -d' ' -f 2`
SPEED=`echo $CONSOLE | cut -d' ' -f 3`

/sbin/getty -L $TTY $SPEED vt100
--------------

I use the above, because I have not just multiple boards,
but multiple platforms each with its own tty name...

[Uwe Kleine-König]

Post by Igor Grinberg
Hi Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

As for fix in userspace, you can spawn getty on every ttymxc*,
so you will get it always.
-----------
CONSOLE=`cat /proc/cmdline | tr " " "\n" | grep console= | tr "=" " " | tr "," " "`
TTY=`echo $CONSOLE | cut -d' ' -f 2`
SPEED=`echo $CONSOLE | cut -d' ' -f 3`
/sbin/getty -L $TTY $SPEED vt100
--------------

what about:

eval "$(sed 's/.*console=\([^,]*\),\([0-9]*\).*/tty=\1; speed=\2/'" /proc/cmdline)"

this should prevent getting a "useless use of cat award".

Best regards
Uwe

[Richard Zhao]

Post by Uwe Kleine-König

Post by Igor Grinberg
Hi Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

As for fix in userspace, you can spawn getty on every ttymxc*,
so you will get it always.
-----------
CONSOLE=`cat /proc/cmdline | tr " " "\n" | grep console= | tr "=" " " | tr "," " "`
TTY=`echo $CONSOLE | cut -d' ' -f 2`
SPEED=`echo $CONSOLE | cut -d' ' -f 3`
/sbin/getty -L $TTY $SPEED vt100
--------------

eval "$(sed 's/.*console=\([^,]*\),\([0-9]*\).*/tty=\1; speed=\2/'" /proc/cmdline)"
this should prevent getting a "useless use of cat award".

Thanks.
Richard

Post by Uwe Kleine-König
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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[Rob Herring]

Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

That's what the aliases are for.

Rob

[Richard Zhao]

Post by Igor Grinberg
Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

That's what the aliases are for.

so, why do I see people define uart aliases in $SOC.dtsi, rather not in $BOARD.dts?

Thanks
Richard

Post by Igor Grinberg
Rob
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[Shawn Guo]

Post by Igor Grinberg
Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

That's what the aliases are for.

I understand it differently. The aliases was introduced to help
tty/serial driver identify the correct hardware port for given serial
node from device tree. (Ab)using it to fool 'console' setting may
eventually confuse users, saying they will think the uart port on his
board is UART0.

[Jason Liu]

Post by Igor Grinberg
Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0"  to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

That's what the aliases are for.

I understand it differently.  The aliases was introduced to help
tty/serial driver identify the correct hardware port for given serial
node from device tree.  (Ab)using it to fool 'console' setting may
eventually confuse users, saying they will think the uart port on his
board is UART0.

We absolutely need document this in detail to avoid confusion. Otherwise,
the ARM DT support will also mess up in the end.

--
Regards,
Shawn
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[Richard Zhao]

Post by Jason Liu

Post by Igor Grinberg
Richard,

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0"  to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

That's what the aliases are for.

I understand it differently.  The aliases was introduced to help
tty/serial driver identify the correct hardware port for given serial
node from device tree.  (Ab)using it to fool 'console' setting may
eventually confuse users, saying they will think the uart port on his
board is UART0.

We absolutely need document this in detail to avoid confusion. Otherwise,
the ARM DT support will also mess up in the end.

Yes, why not come a patch to doc it?

THanks
Richard

Post by Jason Liu

--
Regards,
Shawn
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[Shawn Guo]

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

I'm using Linaro rootfs and do not see this problem at all. So as
people have suggested, you need to fix it in your user space.

[Richard Zhao]

Post by Shawn Guo

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

I'm using Linaro rootfs and do not see this problem at all. So as
people have suggested, you need to fix it in your user space.

Why not past your linaro rootfs solution?

Thanks
Richard

Post by Shawn Guo
--
Regards,
Shawn
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linux-arm-kernel mailing list
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[Shawn Guo]

Post by Richard Zhao

Post by Shawn Guo

Post by Richard Zhao
How to map different uart port to ttymxc0 (take imx for example)?
In rootfs, it usually "getty ttymxc0" to get
serial console. And the rootfs may be shared by different boards.
Traditionaly way is to set right platform device ID.
But with DT, UART2 always generate ttymxc1, UART3 for ttymxc2. You
always needs to modify the getty command when your change another board.
Is there a way to fix it?

I'm using Linaro rootfs and do not see this problem at all. So as
people have suggested, you need to fix it in your user space.

Why not past your linaro rootfs solution?

You do have Linaro rootfs, don't you?