Re: [U-Boot-Users] struct NS16550 {...} attribute ((packed)) at ns16550.h

22 Apr 2005


      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.

Re: [U-Boot-Users] struct NS16550 {...} __attribute__ ((packed)) at ns16550.h

Wolfgang Denk

Re: [U-Boot-Users] struct NS16550 {...} attribute ((packed)) at ns16550.h