Re: [PATCH v4] uartlite: Adding a kernel parameter for the number of uartlites

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On Tue, Feb 14, 2017 at 10:03:08AM -0700, Sam Povilus wrote:
> On Tue, Feb 14, 2017 at 9:36 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Tue, Feb 14, 2017 at 08:59:08AM -0700, Sam Povilus wrote:
> > > The number of uartlites should be set by a kernel parameter instead of
> > > using a #define. This allows the user to set the number of uartlites
> > > using only kconfig and not modifying kernel source.
> > >
> > > The uartlite is used by FPGAs that support a basically unlimited number
> > > of uarts so limiting it at 16 dosn't make sense as users might need more
> > > than that.
> >
> > Shouldn't you bound the size here?  What happens if you ask for 10000
> > uarts?
> >
> > thanks,
> >
> > greg k-h
> 
> Theoretically there is no limit except FPGA hardware and who knows
> what FPGA designers are thinking.  From my understanding fom a kernel
> standpoint it changes the number of  "struct uart_port"s declared
> and therefore the amount of memory used by the module, and how
> much time it takes to do lookup.

There are other internal issues when you try to create zillions of uart
devices, so please, set a sane boundry for this.

How many uarts did you test this patch with?

thanks,

greg k-h
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