Messages in this thread | | | Date | Fri, 14 Jun 2002 14:31:40 +0200 | From | Robert Schwebel <> | Subject | Accessing odd bytes |
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I have a strange effect on an embedded system (AMD Elan SC410, Linux-2.4.18) while accessing a static RAM. The RAM is mapped to the bus at 0x0200'0000. If I map it to user space this way:
pSRAM = (unsigned short *)mmap(0, 0x00040000, PROT_READ + PROT_WRITE, MAP_SHARED, FD, 0x2000000);
and fill it like this:
pByte=(char*)pSRAM; for (i=0; i<10; i++) { *pByte++=(char)i; }
pByte=(char*)pSRAM; for (i=0; i<10; i++) { printf("i: %02i -> %03i\n", i, *pByte++); }
I see a mirroring effect:
i: 00 -> 001 i: 01 -> 001 i: 02 -> 003 i: 03 -> 003 i: 04 -> 005 i: 05 -> 005 i: 06 -> 007 i: 07 -> 007 i: 08 -> 009 i: 09 -> 009
Now I'm wondering how the kernel/processor handles odd byte access exceptions. Can anybody give me a pointer where I could search or what my problem could be?
Robert -- +--------------------------------------------------------+ | Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de | | Pengutronix - Linux Solutions for Science and Industry | | Braunschweiger Str. 79, 31134 Hildesheim, Germany | | Phone: +49-5121-28619-0 | Fax: +49-5121-28619-4 | +--------------------------------------------------------+ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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