Barry Song wrote: > On Fri, Dec 11, 2009 at 10:17 AM, Mike Frysinger <[email protected]> wrote: >> On Thu, Dec 10, 2009 at 21:05, Barry Song wrote: >>> 2009/12/11 David Miller <[email protected]>: >>>> From: Mike Frysinger <[email protected]> >>>>> On Thu, Dec 10, 2009 at 05:48, Wolfgang Grandegger wrote: >>>>>> Wolfgang Grandegger wrote: >>>>>>> Mike Frysinger wrote: >>>>>>>> On Thu, Dec 10, 2009 at 04:11, Wolfgang Grandegger wrote: >>>>>>>>> Well, I'm still not a friend of the following inline functions, >>>>>>>>> especially the *one-liners* which are called just *once*. With the >>>>>>>>> usage >>>>>>>>> of structs they seem even more useless. >>>>>>>> seems like it would make more sense to not even use the read/write >>>>>>>> functions either. �,A just declare the regs as volatile and assign/read >>>>>>>> the struct directly. >>>>>>> Two times no. Don't use volatile and proper accessor functions. See: >>>>>>> >>>>>>> http://lxr.linux.no/#linux+v2.6.32/Documentation/volatile-considered-harmful.txt >>>>>> I was just wondering if bfin_read/write16 would not be the proper >>>>>> accessor functions. readw/writew seems to be implemented differently: >>>>>> >>>>>> http://lxr.linux.no/#linux+v2.6.32/arch/blackfin/include/asm/io.h#L44 >>>>>> >>>>>> Puh, they do an cli,nop,nop,sync..sti for the access. This also nicely >>>>>> shows why accessor functions should be used to access device registers. >>>>>> >>>>>> Well, just curious. I don't really know the blackfin arch. >>>>> the common I/O functions need to account for issues surrounding the >>>>> bus that has arbitrary devices memory mapped to it. on-chip devices >>>>> (like what we're talking about here) do not have these issues and so >>>>> using the common functions is awful overhead. >>>> Then create special accessors (perhaps with the same names as the >>>> existing ones, but with "__" prepended) that lack all of the >>>> interrupt disabling, syncs, etc. >>>> >>>> Really it _is_ cleaner and makes your driver look a lot nicer. >>> I think Mike has said the functions are bfin_read/bfin_write in >>> blackfin arch since those CAN registers are located in memory mapped >>> area but not async memory and have less overhead than common io >>> functions? Is it acceptable to use those functions in this driver? >> yes, bfin_{read,write} should be used > > Wolfgang/David, are you ok with that too? If so, I will send a -v4 > patch using bfin_read/write, with all fix according to your other > comments.
I understood from Mike that these are the proper functions to be used for accessing on-chip registers. Wolfgang. _______________________________________________ Socketcan-core mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-core
