El vie, 15-08-2008 a las 22:46 +0300, Vesa Jääskeläinen escribió: > Javier Martín wrote: > > I take that by "convenient to use" and your earlier "code safety" > > reference, you imply a function that returns a typed pointer to the > > structure, like "bda* var = grub_getbda();" in i386-pc, so that fields > > of such struct can be directly accessed by var->free_mem_kb. > > > > However, this requires that a function is created for each firmware > > structure that is deemed interesting by GRUB developers. In this > > proposal, only one (very lightweight) function is created and then IDs > > are defined for the structs. WRT "code safety", malloc and friends also > > return a void* that you have to cast, so nothing new under the sky. > > In your case there is really no change. > > You create new switch branch (which is most likely implemented by > function somewhere). > > In order to access this void * you have to know its contents. Why not > use structure to define its contents where viable? True, I just wanted to avoid defining structures that would only be used once or twice, but you're right. > > When using malloc() you know that memory returned is not formatted in > anyway. Therefore it is safe to cast. > > You just want to make it more complex that it needs to be in my eyes. > > >> You have still not provided a single GOOD example where this would be > >> used AND would provide some ADDED VALUE. Unless you provide a convincing > >> one (while I pretty much doubt) I do not see this feature to be in our > >> official tree. > > An use case would be in the proposed drivemap module, in the function > > installing an interrupt handler in the real-mode IVT: instead of the > > current code with magic addresses, > > > > /* Real mode IVT slot (seg:off far pointer) for interrupt 0x13. */ > > grub_uint32_t *ivtslot = (grub_uint32_t*)0x0000004c; > > > > The module could be like this: > > > > /* Real mode IVT slot (seg:off far pointer) for interrupt 0x13. */ > > grub_uint32_t *ivtslot = 19 + > > (grub_uint32_t*)grub_machine_get_fwstruct(GRUB_I386_PC_IVT); > > The better way that complies with all your error cases provided: > > grub_ivt_entry_t *entry; > entry = grub_get_ivt_entry(0x13); > *entry = new_value; This was another of the solutions I was considering in this thread (the "many-functions approach"), I just found the single-function solution more elegant in the case of "large numbers" (>10) of structures becoming visible through this method, but your snippet looks fine and "safer".
> > of course grub_ivt_entry_t could be renamed to be something like > grub_realmode_addr_t. grub_realmode_farptr_t would suit better IMO. -Habbit > > . > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > http://lists.gnu.org/mailman/listinfo/grub-devel
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