Wolfgang,

Thanks for your reply. Maybe my configuration was wrong at that time when I compile sources. Now it works as you described. (It was non-sense to me too.) It means "__attribute__((packed))" doesn't affect 4byte access to serial controller.

Thanks, Woojung

Wolfgang Denk wd@denx.de To: Woojung Huh/SMSC@SMSC Sent by: cc: U-Boot-Users@lists.sourceforge.net wd@denx.de Subject: Re: [U-Boot-Users] struct NS16550 {...} __attribute__ ((packed)) at ns16550.h

04/22/2005 02:39 PM

In message OF34DF8405.50E611E8-ON85256FEB.0051A68A-85256FEB.00522DF9@smsc.com you wrote:

We are using u-boot for proprietary ARM board with NS16550 compatible serial controller. It is configured as 4bytes access to serial controller, so set CFG_NS16550_REG_SIZE to 4. But, because of "__attribute__ ((packed))" of struct NS16550, all register accesses to NS16550 are generated to byte access (LDRB, STRB in ARM).

No, this staement makes no sense to me.

I think it should NOT have __attribute__ ((packed)) if NS16550 is configured as 4bytes access. Am I missed something?

I think so.

"__attribute__ ((packed))" only affects the alignment of the entries in the structure. It has no influence on how to access these entries. If your access is a 32 bit read or write access then it will not be changed whether there is a "__attribute__ ((packed))" in place or not.

Best regards,

Wolfgang Denk

-- Software Engineering: Embedded and Realtime Systems, Embedded Linux Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de Every program has at least one bug and can be shortened by at least one instruction -- from which, by induction, one can deduce that every program can be reduced to one instruction which doesn't work.