On Wed, Oct 30, 2024 at 12:28:46PM +0200, Laurent Pinchart wrote: > On Wed, Oct 30, 2024 at 11:25:40AM +0100, Geert Uytterhoeven wrote: > > On Mon, Oct 28, 2024 at 2:34 PM Dmitry Baryshkov wrote: > > > On Tue, Oct 22, 2024 at 07:37:01AM -0700, Doug Anderson wrote: > > > > On Tue, Oct 22, 2024 at 12:12 AM Geert Uytterhoeven wrote: > > > > > > > > > > However, using i2c_client->adapter->nr instead of ida_alloc() > > > > > > > > > > in the TI driver does sound like a good idea to me... > > > > > > > > > > > > > > > > > > Great! > > > > > > > > > > > > > > > With the I2C adapter numbers, that becomes: > > > > > > > > > > > > > > > > /sys/bus/auxiliary/devices > > > > > > > > ├── ti_sn65dsi86.gpio.1 > > > > > > > > ├── ti_sn65dsi86.pwm.1 > > > > > > > > ├── ti_sn65dsi86.aux.1 > > > > > > > > ├── ti_sn65dsi86.bridge.1 > > > > > > > > ├── ti_sn65dsi86.gpio.4 > > > > > > > > ├── ti_sn65dsi86.pwm.4 > > > > > > > > ├── ti_sn65dsi86.aux.4 > > > > > > > > └── ti_sn65dsi86.bridge.4 > > > > > > > > > > > > > > > > > adapter->nr instead like other aux subsystems already do. > > > > > > > > > > > > > > Unfortunately the devil is in the details, as usual: there can be > > > > > > > multiple instances of the sn65dsi86 bridge on a single I2C bus, > > > > > > > so adapter->nr is not guaranteed to generate a unique name. > > > > > > > > > > > > In the case of sn65dsi86 I think we'd actually be OK. The TI bridge > > > > > > chip is always at bus address 0x2d so you can't have more than one on > > > > > > the same bus. Unless you added something funky atop it (like a mux of > > > > > > some sort) you might be OK. > > > > > > > > > > It's 0x2c on mine ;-) > > > > > > > > > > 8.5.1 Local I2C Interface Overview > > > > > The 7-bit device address for SN65DSI86 is factory preset to 010110X > > > > > with the least significant bit being determined by the ADDR control > > > > > input. > > > > > > > > Doh! I missed that in my search of the doc. I guess because they > > > > decided to specify the address in binary in that part so my searching > > > > for both the 7-bit and 8-bit I2C address didn't trigger. Oh well. > > > > > > > > > > > Changing the auxiliary bus to use the parent's name instead of the > > > > > > > module name, as suggested by Laurent, would fix that. > > > > > > > > > > > > Right. On my system dev_name() of the sn65dsi86 device is "2-002d". If > > > > > > we had a second on i2c bus 4, we'd have: > > > > > > > > > > > > /sys/bus/auxiliary/devices > > > > > > ├── 2-002d.gpio.0 > > > > > > ├── 2-002d.pwm.0 > > > > > > ├── 2-002d.aux.0 > > > > > > ├── 2-002d.bridge.0 > > > > > > ├── 4-002d.gpio.0 > > > > > > ├── 4-002d.pwm.0 > > > > > > ├── 4-002d.aux.0 > > > > > > └── 4-002d.bridge.0 > > > > > > > > > > > > ...and I think that's guaranteed to be unique because all the i2c > > > > > > devices are flat in "/sys/bus/i2c/devices". > > > > > > > > > > Correct. > > > > > > > > So given everything, using the dev_name() of the "parent" sounds > > > > pretty good and seems like it addresses everyone's concerns. Was there > > > > a part of the conversation where someone pointed out problems with it > > > > that I missed? Is the next step to post a patch implementing that? > > > > It'll change sysfs paths and dev names for everyone using AUX bus, but > > > > presumably that's OK? > > > > > > It also requires changing in the way the auxiliary_match_id() works. > > > Currently matching is done using modname + ID. > > > > Right, so just using the parent's name instead of modname won't work, > > as the former is not a fixed string. > > > > > So, maybe using MODNAME.NAME.parent-name.ID is better (e.g. > > > ti_sn65dsi86.gpio.2-002d.1). It will still require changes to the > > > match_id function, but they won't be that intrusive (one just has to > > > skip two parts of the name instead of skipping just one). > > > > IMHO this is becoming too complex. What if the parent's name contains > > a period? > > > > So just using ida_alloc() in the caller seems like the most > > straight-forward solution. > > Why would we duplicate that in every user, when it should really be the > responsibility of the bus ? We need a better solution. Make AUX bus keep a hashtable of parent -> ID relationship and get from the table / allocate via IDA the ID each time somebody adds new AUX device? -- With best wishes Dmitry
