PROCESSOR-SDK-AM62X: Based on AM62x - Consultation on Devmem2 Tool Issues

?? ? said:

A file system built on yocto, with built-in devmem2, can read odd addresses normally:

If you look at the Yocto recipe for the devmem2 tool we are using in our SDKs located at ./meta-openembedded/meta-oe/recipes-support/devmem2/devmem2_2.0.bb...

SUMMARY = "Simple program to read/write from/to any location in memory"
LICENSE = "GPL-2.0-or-later"
LIC_FILES_CHKSUM = "file://devmem2.c;endline=38;md5=a9eb9f3890384519f435aedf986297cf"

SRC_URI = "git://github.com/denix0/devmem2.git;protocol=https;branch=main"
SRCREV = "5b395a946894eb4f4ef5d07c80a50a88573a541e"

S = "${WORKDIR}/git"

CFLAGS += "-DFORCE_STRICT_ALIGNMENT"

do_compile() {
    ${CC} -o devmem2 devmem2.c ${CFLAGS} ${LDFLAGS}
}

do_install() {
    install -d ${D}${bindir}
    install devmem2 ${D}${bindir}
}

You can find the server where it resides and the source revision https://github.com/denix0/devmem2

Then if you notice how the Yocto recipe sets a build flag called FORCE_STRICT_ALIGNMENT, which when you look at the source code will explain the "more tolerant" behavior you observed:

From https://github.com/denix0/devmem2/blob/main/devmem2.c ...

static inline void *fixup_addr(void *addr, size_t size)
{
#ifdef FORCE_STRICT_ALIGNMENT
	unsigned long aligned_addr = (unsigned long)addr;
	aligned_addr &= ~(size - 1);
	addr = (void *)aligned_addr;
#endif
	return addr;
}

Regards, Andreas