On Mon, Nov 18, 2013 at 03:14:41PM +0100, Jean Delvare wrote: > Hi Guenter, > > On Sun, 17 Nov 2013 13:13:43 -0800, Guenter Roeck wrote: > > On 11/17/2013 12:41 PM, Jean Delvare wrote: > > > On Sun, 17 Nov 2013 10:56:24 -0800, Guenter Roeck wrote: > > >> This retains the old mux name if the mux is not an i2c device, and adds > > >> the i2c device address if it is. This solves the problem for me. > > >> > > >> Comments ? > > > > > > This "for me" worries me a bit. You basically restored the uniqueness > > > for the multiple I2C-based multiplexer case. But for multiple > > > GPIO-based multiplexers, for example, the name confusion still exists. > > > > Only if some genius connects multiple separate gpio based multiplexers > > to the same bus. > > This is totally possible, for a variety of reasons, including physical > location of the GPIO pins and bus segment ends, but also economical > (using the same chips on several boards.) > Ok. > > In practice, though, that can be modeled as single > > gpio mux with more pins, so I didn't think that is that much of a problem. > > I admit I had not considered this. But would it work if the different > GPIO pins are on different chips (say south bridge and Super-I/O for > example)? The i2c-mux-gpio driver assumes a single chip, at least when > passed by name. > ... so you could or should not pass a name if that is the case. > > > If we are going to address this problem, I believe we should do so in a > > > way which doesn't need revisiting in a couple months. You are changing > > > adapter names people or tools may be relying on, we really don't want > > > to do this too often. > > > > Good point. One possible solution might be to add the mux type into the name. > > i2c-2-mux-i2c-76 (chan_id 0) > > i2c-2-mux-gpio-77 (chan_id 0) > > Yes, that's pretty much what I had in mind. > > > We could add an additional parameter to the API, such as > > const char *qualifier > > to provide the "i2c-76" or "gpio-77" string. If the qualifier is NULL, > > the name would revert to the old naming scheme. Would that make sense ? > > Yes, although your first draft gave me some hope that i2c-mux could do > some magic to guess the type and identifier automatically. But maybe > it's not that clean to have to touch i2c-mux for every new i2c-mux-* > driver. Not that I expect too many of them... so it's mostly a matter > of principle. An explicit qualifier as you suggest above might be > cleaner. > Another option would be to use the patch I provided, except to create names such as i2c-2-mux-i2c-76. The API change could then be added later if/as needed. But, yes, an API change would be cleaner. Before I submit a "final" patch, it would be great to get feedback and direcetion from Wolfram ... after all, he'll have to approve it at the end. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
