Re: Memory-mapped peripheral registers, remote protocol and memory maps

[Yao Qi <yao at codesourcery dot com>]

On 11/29/2012 03:23 AM, Jon Beniston wrote:
> How is the access of memory-mapped peripheral registers handled over the
> remote protocol? By this, I mean how can you force a 32-bit read/write,
> rather than 4 byte accesses, to read/write a 32-bit memory-mapper register?
>
> I can see that you can define memory regions with the mem command, and set
> the memory access size to 32, but how does this map over the remote
> protocol?   The remote protocol documentation for the 'm' packet says: "The
> stub need not use any particular size or alignment when gathering data from
> memory for the response; even if addr is word-aligned and length is a
> multiple of the word size, the stub is free to use byte accesses, or not.
> For this reason, this packet may not be suitable for accessing memory-mapped
> I/O devices.". Is there another packet that is suitable? It doesn't look
> like the code in remote.c uses this attribute.

I don't understand your problem.  Anything wrong when you use 'm' packet 
to read the content of memory-mapped register?  Supposing a 32-bit 
register is mapped at address 0x00d000, packet 'm 0x0x00d000 4' should 
be able read the contents of this register.  Your stub should know where 
each register is mapped, and when gets a 'm' packet, get the content of 
register by some way, and reply it to GDB.  In this way, the 
memory-mapped registers are transparent to GDB, and user has to access 
them via address.

--
Yao (éå)