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Scholar vanmierlo
Scholar
9,489 Views
Registered: ‎06-10-2008

what are all those /dev/tty's ?

Hi,

 

When I build a petalinux 2014.4 setup for a Zynq I see one tty in /dev/ and 64 ttyN devices. What are they (supposed to be) connected to? There is also ttyPS0 (and possibly ttyPS1) which is/are the ARM native uart. And if I add a uartlite to the PL I also get ttyUL0. So it's not these they're pointing to.

 

Maarten

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6 Replies
Xilinx Employee
Xilinx Employee
9,481 Views
Registered: ‎08-01-2008

Re: what are all those /dev/tty's ?

You can below ARs

http://www.xilinx.com/support/answers/63280.html
Thanks and Regards
Balkrishan
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Scholar sampatd
Scholar
9,476 Views
Registered: ‎09-05-2011

Re: what are all those /dev/tty's ?

The Linux kernel subsystem comprises of Character, Block, and Network drivers. The char and block drivers are present as device files in /dev. A char driver is one that can be accessed as a stream of bytes - /dev/ttyxx usually represent character drivers in the kernel.

The Zynq PS uart1 shows up as /dev/ttyPS0 in the kernel.

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Scholar vanmierlo
Scholar
9,469 Views
Registered: ‎06-10-2008

Re: what are all those /dev/tty's ?

@balkris Thanks, interesting article but it says nothing about /dev/ttyxx only /dev/ttyPS0.

 

@sampatd I know that /dev/ttyxx represent character devices. My question is: what are these ones pointing to? I don't believe I have any other character devices that would qualify as a /dev/tty, but otherwise I would like to know which. Or are these some sort of mount points that newly plugged-in devices can take over? Not my experience. If I plug in a USB-UART it gets yet another /dev/ttyUSBx entry. So what's the use these 65 entries?

 

Maarten

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Xilinx Employee
Xilinx Employee
9,444 Views
Registered: ‎12-17-2007

Re: what are all those /dev/tty's ?

This is a general Linux question. Perhaps this can clarify it for you:

http://superuser.com/questions/449781/why-is-there-so-many-linux-dev-tty
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Scholar vanmierlo
Scholar
9,438 Views
Registered: ‎06-10-2008

Re: what are all those /dev/tty's ?

Ok, thanks. But what are they doing in my Zynq embedded linux? I have no keyboard with Ctrl, Alt or F2 keys. I also have no display. And even if I had, how would I press Ctrl-Alt-F63? Pressing Ctrl-Alt-F2 in a PuTTY SSH connection doesn't do anything. And neither does this in TeraTerm connected to the UART (ttyPS0). I still feel like most of them should disappear.

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Scholar milosoftware
Scholar
9,424 Views
Registered: ‎10-26-2012

Re: what are all those /dev/tty's ?

There's a kernel option to make them go away. I don't recall which one though.

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