Re: [PATCH v2] serial_core: fix uart PORT_UNKNOWN handling

[One Thousand Gnomes]

On Wed, 23 Apr 2014 12:33:22 +0200
Thomas Pfaff <tpfaff@xxxxxxx> wrote:

> From: "Thomas Pfaff" <tpfaff@xxxxxxx>
> 
> While porting a RS485 driver from 2.6.29 to 3.14, i noticed that the serial tty 
> driver could break it by using uart ports that it does not own :
> 
> 1. uart_change_pm ist called during uart_open and calls the uart pm function
>    without checking for PORT_UNKNOWN.
>    The fix is to move uart_change_pm from uart_open to uart_port_startup.
> 2. The return code from the uart request_port call in uart_set_info is not
>    handled properly, leading to the situation that the serial driver also
>    thinks it owns the uart ports.
>    This can triggered by doing following actions :
> 
>    setserial /dev/ttyS0 uart none    # release the uart ports
>    modprobe lirc-serial              # or any other device that uses the uart
>    setserial /dev/ttyS0 uart 16550   # gives no error and the uart tty driver
>                                      # can use the ports as well
> 
> Signed-off-by: Thomas Pfaff <tpfaff@xxxxxxx>
Reviewed-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
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