[Fault-injection-developer] RE: [BUG] [2.5.49] symbol_get doesn't work

[Wang, S. <sta...@in...>]

Hi, Rusty
I get it now :)

Thanks,
Stanley

> -----Original Message-----
> From: Rusty Russell [mailto:ru...@ru...]
> Sent: 2002=E5=B9=B411=E6=9C=8829=E6=97=A5 8:02
> To: Wang, Stanley
> Cc: 'lin...@vg...'; dw...@tw...
> Subject: Re: [BUG] [2.5.49] symbol_get doesn't work=20
>=20
>=20
> In message=20
> <957...@pd...> you
>  write:
> > Hi, Rusty
> > Thanks for your respondence.
> > You means that the purpose of using symbols_get() is just adding =
=3D
> > module's
> > reference count, right?
> > If so, I think we don't need a pointer to be returned by=20
> symbol_get(). =3D
> > We
> > could use the symbols desired
> > directly after we called symbol_get().=3D20
> > How do you think about it ?
>=20
> Hi Wang,
>=20
> 	No, you do *not* normally need to use symbol_get(): you just
> use the symbol like normal and the loader will make sure reference
> counts are adjusted etc.
>=20
> 	Here's an example of use, from my (completely untested) "make
> mtd use symbol_get()" patch, which allows mtd to look for support for
> a given command set at runtime (rather than forcing all command set
> modules to be present to load at all):
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> typedef struct mtd_info *cfi_cmdset_fn_t(struct map_info *, int);
> =20
> static struct mtd_info *unknown_cmdset(struct map_info *map,=20
> int primary)
> {
> 	struct cfi_private *cfi =3D map->fldrv_priv;
> 	__u16 type =3D primary?cfi->cfiq->P_ID:cfi->cfiq->A_ID;
>=20
> 	printk(KERN_NOTICE "Support for command set %04X not present\n",
> 	       type);
> 	return NULL;
> }
>=20
> /* when we are built without module support, so we still link */
> cfi_cmdset_fn_t cfi_cmdset_0001 __attribute__((weak,=20
> alias("unknown_cmdset")));
> cfi_cmdset_fn_t cfi_cmdset_0002 __attribute__((weak,=20
> alias("unknown_cmdset")));
> cfi_cmdset_fn_t cfi_cmdset_0003 __attribute__((weak,=20
> alias("unknown_cmdset")));
>=20
> static inline struct mtd_info *cfi_cmdset_unknown(struct=20
> map_info *map,=20
> 						  int primary)
> {
> 	struct cfi_private *cfi =3D map->fldrv_priv;
> 	__u16 type =3D primary?cfi->cfiq->P_ID:cfi->cfiq->A_ID;
> 	cfi_cmdset_fn_t *probe_function =3D NULL;
>=20
> 	switch (type) {
> 	case 1:
> 		probe_function =3D symbol_get(cfi_cmdset_0001);
> 		break;
> 	case 2:
> 		probe_function =3D symbol_get(cfi_cmdset_0002);
> 		break;
> 	case 3:
> 		probe_function =3D symbol_get(cfi_cmdset_0003);
> 		break;
> 	}
> 	if (probe_function) {
>  		struct mtd_info *mtd;
> =20
>  		mtd =3D (*probe_function)(map, primary);
>  		return mtd;
>  	}
> 	return unknown_cmdset(map, primary);
>  }
> =20
> --
>   Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
>=20