Re: [PATCH v1] PowerPC: Add support for Dense Math registers (RFC02653)

[Ulrich Weigand <Ulrich.Weigand@de.ibm.com>]

Abhay Kandpal <abhay@linux.ibm.com> wrote:
 
>The existing names encode the base ISA level, but DMR is a later ISA
>feature layered on an isa207-derived description, so isa207-dmr would 
>misstate the ISA level. A few options:
>
>1. powerpc-isa207-dmr-vsx64l - names the base feature set the description extends
>2. powerpc-isa32-dmr-vsx64l - names DMR's own ISA level (ISA 3.2)
>3. powerpc-dmr-vsx64l - as posted, no ISA level

I'm not familiar with ISA 3.2 - is DMR mandatory or optional in 3.2?
And are there any *other* 3.2 features that GDB needs to implement?

I'd prefer "powerpc-isa32-vsx64l" to refer to an implementation of
all mandatory features (including DMR if mandatory), and if DMR is
optional, then in addition "powerpc-isa32-dmr-vsx64l" for the
combination of mandatory ISA 3.2 features plus DMR.

 
>So in v2 I'll convert the native side to the regset mechanism
>throughout: fetch_regset/store_regset with NT_PPC_DMR in
>fetch_register, fetch_ppc_registers, store_register and
>store_ppc_registers, and a regset-based availability check in
>read_description. That removes the need for the 
>PTRACE_GETDMREGS/PTRACE_SETDMREGS defines, so I'll drop the 
>block rather than move it - unless something still needs them,
>in which case I'll relocate it as you suggest.

No, if they're not needed, it's better to drop these defines.

>Yes - PPC_FEATURE2_DMF (0x00008000, Dense Math Facility). I'll add
that
>check. The kernel does save and restore these registers across context 
>switches. The hwcap bit and the DMR ptrace support are currently in 
>separate kernel branches here, so I'm assembling a tree with both before
>validating v2.

Thanks!

Bye,
Ulrich