Re: [PATCH 1/1] xilinx ps uart: Adding a kernel parameter for the number of xilinx ps uarts

[Alan Cox]

> We have in soc vendor tree similar patch but the reason is different.
> 
>     tty: serial: Added a CONFIG_SERIAL_XILINX_NR_UARTS option.
> 
>     This patch Adds CONFIG_SERIAL_XILINX_NR_UARTS option to allow
>     the user to provide the Max number of uart ports information.
>     If multiple cards (or) PL UARTS are present, the default limit
>     of 2 ports should be increased.
> 
> I haven't checked all drivers but in our case we have added this as
> quick fix for scenarios where you use serial aliases where alias is
> pointed to serial2 or more.
> In cdns_uart_init() cdns_uart_uart_driver is passed which contains .nr
> which is required to be passed.
> 
> What's the best driver to look at dynamic allocation?

So there are quite a few that dynamically allocate the objects as they
are enumerated (eg max3100), but have a maximum set that is just pointers
(so for the max number of ports cheaper than the dynamic code)

The other question is why is it a CONFIG_ option. I'm assuming these
platforms are all ARM and in that case you could just pass the value in
the device tree, or hard code a safe maximum number of pointers to a
value which is the worst case and then install them as they are
enumerated.

There are lots of options better than breaking the "one kernel many
platforms" model.

Alan