[PATCH 7/8] i2c: add 'transferred' field to struct i2c_msg

On Sat, Oct 27, 2012 at 06:02:35PM +0100, Al Viro wrote:

On Sat, Oct 27, 2012 at 05:40:13PM +0100, Al Viro wrote:

quoted

You are wrong.  Assumption that pointers are aligned to 32bit boundary
is simply not true.  In particular, on m68k alignment is 16bit, i.e. there
struct foo {
	char x;
	void *p;
}; will have 1 byte occupied by x, followed by 1-byte gap, followed by 4 bytes
occupied by p.

Note, BTW, that m68k includes things like coldfire, etc. and I wouldn't be
surprised by e.g. coldfire-based SoC with i2c on it.

BTW, that's easily verified - take a cross-compiler and do this:
; cat >a.c <<'EOF'
struct { char x; void *y; } v;
int z = (char *)&v.y - (char *)&v;
EOF
; m68k-linux-gnu-gcc -S a.c
; grep -A1 'z:' a.s
z:
        .long   2
;
and watch what it puts into z.  gcc is very liberal about what it considers
a constant expression, so it allows that sort of expressions as initializers
for global variables.  Not a portable C, but convenient for experiments like
that; just grab a cross-toolchain and feed it testcases of that kind...

... and google for i2c coldfire immediately turns up this:
http://mailman.uclinux.org/pipermail/uclinux-dev/2012-May/051874.html
with
+config I2C_COLDFIRE
+       tristate "Freescale Coldfire I2C driver"
+       depends on !M5272
+       help
+         This driver supports the I2C interface availible on most Freescale
+         Coldfire processors.
+
+         This driver can be built as a module.  If so, the module
+         will be called i2c-coldfire.

in it, along with addition of drivers/i2c/busses/i2c-coldfire.c...  IOW,
i2c on m68k is quite real.  Sorry, no go - you don't even have an excuse
of i2c never existing on the architecture in question.