Jean Delvare wrote: > Hi Mark, > > >>This is a good time to bring up the i2c-virtual driver as an >>alternative to the -s4882.c style of multiplexing driver. I believe >>this is a cleaner and more general approach to bus multiplexing. > > > I agree it is more general, and possibly cleaner as a result. However, > it will fail to be as flexible as the s4882 style approach. > > The S4882 has 8 busses, 2 for each CPU. The 2 busses of each CPU are > "compatible" (no common address) so I merged them, which results in > better performance (less switching required) and lower memory footprint. > I don't think you'll be able to do that with the i2c-virtual approach. > > In the NCLV-D case, it has 4 different bus lines, but we only really > want to handle 2. How can you do that with i2c-virtual? > i2c-virtual is the generic part. It would be handled in a new nclv-d module for the specifics of that board. > Also, I think I remember that i2c-virtual somehow assumes that the > multiplexer itself is an i2c chip, right? This is not the case for the > NCLV-D. > no the mux itself can be anything. It is controlled by another driver which does the specific switching. See pca954x.c. i2c-virtual.c only contains the generic part. While pca954x is large, it is overly complex and needs a lot of cleanup. I belive a module for NCLV could be fairly small. > > >>The i2c-virtual driver is checked in to sensors but the small changes >>required to i2c-core.c are not checked in. I held off late last year >>because 2.9.0 was coming out soon. Now that 2.9.1 is out it's time to >>look at it again. I have to rework the i2c-core changes because they >>conflicted with other recent changes to i2c-core. > > > Yeah, I remember that. > > The more I think of it, the more obvious it is that such a change > doesn't belong to the 2.4 kernel, but 2.6. I do not want any more > changes to the i2c subsystem of Linux 2.4 (except for bug fixes and > documentation updates, of course). It's more than time to move the > development effort to 2.6, and only do support on 2.4. > > well it's a modest change and CVS / 2.4 is a better sandbox to test out the changes, at least for me. 2.4 was where the virtual driver was developed by the original submitter Ken Harrenstein. >>attached are the proposed changes to i2c-core for comment. > > > Eerk. By brain doesn't read non-unified patches very well, sorry. > eerk :) here is unified diff -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: i2c-core.diff Url: http://lists.lm-sensors.org/pipermail/lm-sensors/attachments/20050418/2660b11b/attachment.pl
