[PATCH v2 09/13] tftp: implement 'windowsize' (RFC 7440) support

[Sascha Hauer]

On Tue, Aug 09, 2022 at 11:28:16AM +0200, Enrico Scholz wrote:
> Sascha Hauer <sha at pengutronix.de> writes:
> 
> >> +config FS_TFTP_MAX_WINDOW_SIZE
> >> +	int
> >> +	prompt "maximum tftp window size (RFC 7440)"
> >> +	depends on FS_TFTP
> >> +	default 128
> >> +	range 1 128
> >> +	help
> >> +	  The maximum allowed tftp "windowsize" (RFC 7440).  Higher
> >> +	  value increase speed of the tftp download with the cost of
> >> +	  memory (1432 bytes per slot).
> >> +
> >> +	  Requires tftp "windowsize" (RFC 7440) support on server side
> >> +	  to have an effect.
> >
> > Can we agree on some sane default here and drop this from Kconfig?
> 
> I think, it is difficult to find a sane default.  Processors like iMX8
> can deal with large window sizes, but low end ones like iMX6ULL can not
> handle data fast enough and require smaller sizes (around max 30).
> 
> Workloads like writing to slow memory (cp /mnt/tftp/... /dev/nand) might
> require smaller sizes too.  Or networks with high drop rates.
> 
> That's why, I think it should be possible to configure it in some
> _defconfig.

It's exposed to global.tftp.windowsize and with this you can store a
good value on the device and you can provide different defaults for different
boards in their default environments during compile time. It's much more
flexible than Kconfig.

Sascha

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