Am 07.05.2013 13:36, schrieb Wolfgang Denk:
Dear Dirk Eibach,
In message cf2913653766edc89705f49e08758df7@gdsys.cc you wrote:
OK - but I don't see why mclink_send() could not be used in the same way, i. e. taking a struct member as argument?
Certainly it *can* be used using *pointers* to struct members as argument.
What I stated yesterday was: "We have FPGAs that are memory mapped and others that are not. They must be accessed by the same drivers. So the alternative would be to create FPGA instances at address NULL and getting the register offesets by casting pointers to u16. Not very nice either."
Yes, you wrote that. I did not understand it then, nor do I understand it now. What do you mean by "create FPGA instances at address NULL"? in any case, "getting the register offsets by casting pointers to u16" makes no sense, as this is exactly what we try to avoid. By referencing a C struct you do NOT use any offsets. You use references to struct elements; where needed, you let the compiler to the address calculations (and the type checking).
No offsets. No casts.
OK. Once more. 3 of our 4 FPGAs are *not* memory mapped. There is no base address. This is what I want to show by:
struct ihs_fpga system_fpgas[] = { (struct ihs_fpga *)CONFIG_SYS_FPGA_BASE(0), (struct ihs_fpga *)NULL, (struct ihs_fpga *)NULL, (struct ihs_fpga *)NULL, };
For accessing registers of those (not memory mapped) FPGAs I need an u16 register-index. That is what I want to show by:
mclink_send(fpga - 1, (u16)addr, data);
This is the cast I am talking about.
This is the reason why I still need the fpga index parameter.
Cheers Dirk