Steve, Please keep list C-C'd, On Sat, Sep 26, 2009 at 12:13 PM, Steve Sakoman <sako...@gmail.com> wrote:
> On Sat, Sep 26, 2009 at 9:02 AM, Ben Warren <biggerbadder...@gmail.com> > wrote: > > Hi Olof, > > On Sat, Sep 26, 2009 at 8:53 AM, Olof Johansson <o...@lixom.net> wrote: > >> > >> On Sep 26, 2009, at 1:13 AM, Dirk Behme wrote: > >> > >>> Olof Johansson wrote: > >>>> > >>>> Add setup for ethernet on Tobi, allowing kernel/ramdisk to be loaded > >>>> over tftp. > >>>> Based on the omap3 evm code. I added a new highlevel define for Tobi > >>>> to avoid having it dependent on CMD_NET (which would seem backward in > >>>> this case). > >>> > >>> First: This is only a request for comment for possible future > >>> improvement. It doesn't ask for any changes in this patch or is any > nack. > >>> Now to the content ;) > >>> > >>> It seems that Steve found a way for runtime detection of smc911x making > >>> CONFIG_OMAP3_OVERO_TOBI more or less obsolete (from [1]) : > >> > >> Looks like a good idea. I guess the risk is if there's ever another > >> carrier board with something on the same chip select that happens to > return > >> something at that address, thus causing false detection. Is that a valid > >> concern? > >> > > It is a good idea in principle, but just reading and expecting > *something* > > is a fatal flaw. I don't know about these ones in particular, but > > memory-mapped chips often have ID registers that are RO and have > > well-documented contents. If somebody can find something like that here, > > let's do it. > > Agreed, I didn't have a spec at hand to investigate this, so that's > why I didn't think that this was a good patch for all systems with > smc911x. I know it to work on Overo because reads to non-existent > GPMC locations give all ones (hence the test for -1). > > I would definitely prefer a register with known contents. > > There was a question as to whether the code returned the proper value. > Returning a 0 from this routine when no chip is found results in a > reasonable error message: > > Net: No ethernet found. > > Yes, returning 0 is the correct value. The undocumented API is that Ethernet initialize() functions return the number of interfaces added, or -1 on error. I wouldn't consider this an error condition. regards, Ben
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