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Re: [avr-libc-dev] Inclusion of far pointer library (patch #6352)broke a

From: Jan Waclawek
Subject: Re: [avr-libc-dev] Inclusion of far pointer library (patch #6352)broke avr-libc build
Date: Sun, 13 Jun 2010 22:15:14 +0200

>Regarding the linker script section names, that should certainly be
>mentioned in the description (so it eventually goes into the avr-libc
>documentation), independent of whether Eric provides a patch in the
>next version of the WinAVR successor.  Can you please submit a
>paragraph for that, Jan?

It's all in an avrfreaks.net thread linked from 
https://savannah.nongnu.org/bugs/?26365 , namely 

Around two thirds down, search for "linker script".

Maybe a bit more narrative than standard documentation, but I wanted to spawn a 
discussion first, I did not expect it will be included that soon.

._progmem_far (together with PFSTR macro and the xxx_PF() functions) is 
intended to provide a relatively easy and transparent relief from a pressure on 
the lower 64k FLASH by moving mainly strings to above the .data initialisers. 

._progmem_segment1 etc: "The purpose of "segmented" usage is to allow for 
faster and more comfortable address calculation, if we know beforehand that we 
can fit all FLASH data into a 64k "segment", (segment1 is 0x10000-0x1FFFF, 
segment2 is 0x20000-0x2FFFF, segment3 is 0x30000-0x3FFFF). To access them, we 
still need the pgm_read_xxx_far() (and xxx_PF()) family, but we can use the 
"native" pointer mechanism and then add the segment address."

Is this sufficient enough?


PS. Sorry for the late response, couldn't get to computer sooner.

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