Re: [RFC][PATCH] powerpc: Use the #address-cells information to parsememory/reg

[Suzuki Poulose]

On 06/06/11 14:21, Sebastian Andrzej Siewior wrote:
> Suzuki Poulose wrote:
> > Could you please let me know your thoughts/comments about this patch ?
>
> I'm mostly fine with it.
>
> Maaxim copied fs2dt.c from ppc64 to ppc. So I guess ppc64 has the same
> problem.

Yes, you are right. Porting this patch over to ppc64 is in my TODO list.

> ARM and MIPS is soon having DT support and kexec is probably also
> on their list so I would hate to see them to either copy the DT parsing
> file or having their own implementation.
>
> Maybe we should try to use libfdt for dt parsing. It has /proc import
> support so it should be fine for our needs. It is already in tree and used
> by ppc32 if a basic dtb is specified. I'm not sure if the /proc interface
> is part of dtc or libfdt.
>
> I'm not saying this has to be done now but maybe later before ARM and/or
> MIPS comes along needs something similar for their needs. If the libfdt is
> too complex for sucking in the dtb from /proc then maybe something else
> that generic and can be shared between booth ppc architectures and the
> other ones.
OK

> > > Index: kexec-tools-2.0.4/kexec/arch/ppc/kexec-ppc.c
> > > ===================================================================
> > > --- kexec-tools-2.0.4.orig/kexec/arch/ppc/kexec-ppc.c
> > > +++ kexec-tools-2.0.4/kexec/arch/ppc/kexec-ppc.c
> > > @@ -34,6 +35,92 @@ unsigned int rtas_base, rtas_size;
> > > int max_memory_ranges;
> > > const char *ramdisk;
> > >
> > > +/*
> > > + * Reads the #address-cells and #size-cells on this platform.
> > > + * This is used to parse the memory/reg info from the device-tree
> > > + */
> > > +int init_memory_region_info()
> > > +{
> > > + size_t res = 0;
> > > + FILE *fp;
> > > + char *file;
> > > +
> > > + file = "/proc/device-tree/#address-cells";
> > > + fp = fopen(file, "r");
> > > + if (!fp) {
> > > + fprintf(stderr,"Unable to open %s\n", file);
> > > + return -1;
> > > + }
> > > +
> > > + res = fread(&dt_address_cells,sizeof(unsigned long),1,fp);
> > > + if (res != 1) {
> > > + fprintf(stderr,"Error reading %s\n", file);
> > > + return -1;
> > > + }
> > > + fclose(fp);
> > > + dt_address_cells *= sizeof(unsigned long);
>
> This should be sizeof(unsigned int). I know we on 32bit.
OK. I was using (unsigned long) to get the word size on the machine. Given
this code is duplicated in ppc64, thought of having a generic code which works
fine for all ppcXX. As you mentioned, if we go about moving to a single copy of
fdt code, using long would help us.

> > > + file = "/proc/device-tree/#size-cells";
> > > + fp = fopen(file, "r");
> > > + if (!fp) {
> > > + fprintf(stderr,"Unable to open %s\n", file);
> > > + return -1;
> > > + }
> > > +
> > > + res = fread(&dt_size_cells,sizeof(unsigned long),1,fp);
> > > + if (res != 1) {
> > > + fprintf(stderr,"Error reading %s\n", file);
> > > + return -1;
> > > + }
> > > + fclose(fp);
> > > + dt_size_cells *= sizeof(unsigned long);
>
> same here.

Thanks
Suzuki
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/