Hi Greg, On Mon, Oct 21, 2024 at 8:39 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > On Sun, Oct 20, 2024 at 05:36:29PM +0300, Laurent Pinchart wrote: > > On Fri, Oct 18, 2024 at 04:31:21PM +0200, Greg KH wrote: > > > On Fri, Oct 18, 2024 at 05:25:22PM +0300, Laurent Pinchart wrote: > > > > On Fri, Oct 18, 2024 at 04:09:26PM +0200, Greg KH wrote: > > > > > On Fri, Oct 18, 2024 at 03:36:48PM +0200, Geert Uytterhoeven wrote: > > > > > > On Fri, Oct 18, 2024 at 3:10 PM Laurent Pinchart wrote: > > > > > > > On Fri, Oct 18, 2024 at 09:45:52AM +0200, Geert Uytterhoeven wrote: > > > > > > > > Each bridge instance creates up to four auxiliary devices with different > > > > > > > > names. However, their IDs are always zero, causing duplicate filename > > > > > > > > errors when a system has multiple bridges: > > > > > > > > > > > > > > > > sysfs: cannot create duplicate filename '/bus/auxiliary/devices/ti_sn65dsi86.gpio.0' > > > > > > > > > > > > > > > > Fix this by using a unique instance ID per bridge instance. > > > > > > > > > > > > > > Isn't this something that should be handled by the AUX core ? The code > > > > > > > below would otherwise need to be duplicated by all drivers, which seems > > > > > > > a burden we should avoid. > > > > > > > > > > > > According to the documentation, this is the responsibility of the caller > > > > > > https://elixir.bootlin.com/linux/v6.11.4/source/include/linux/auxiliary_bus.h#L81 > > > > > > I believe this is the same for platform devices. > > > > > > See also the example at > > > > > > https://elixir.bootlin.com/linux/v6.11.4/source/include/linux/auxiliary_bus.h#L116 > > > > > > > > > > > > Note: the platform bus supports PLATFORM_DEVID_AUTO, but the auxiliary > > > > > > bus does not. > > > > > > > > > > Yes, it does not as it's up to the caller to create a unique name, like > > > > > your patch here does. I'd argue that platform should also not do > > > > > automatic device ids, but that's a different argument :) > > > > > > > > __auxiliary_device_add() creates the device name with > > > > > > > > dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id); > > > > > > > > I'm not calling for a PLATFORM_DEVID_AUTO-like feature here, but > > > > shouldn't the first component of the device name use the parent's name > > > > instead of the module name ? > > > > > > Why would the parent's name not be the module name? That name is > > > guaranteed unique in the system. If you want "uniqueness" within the > > > driver/module, use the name and id field please. > > > > > > That's worked well so far, but to be fair, aux devices are pretty new. > > > What problem is this naming scheme causing? > > > > Auxiliary devices are created as children of a parent device. When > > multiple instances of the same parent type exist, this will be reflected > > in the /sys/devices/ devices tree hierarchy without any issue. The > > problem comes from the fact the the auxiliary devices need a unique name > > for /sys/bus/auxialiary/devices/, where we somehow have to differenciate > > devices of identical types. > > > > Essentially, we're trying to summarize a whole hierarchy (path in > > /sys/devices/) into a single string. There are different ways to solve > > this. For platform devices, we use a device ID. For I2C devices, we use > > the parent's bus number. Other buses use different schemes. > > > > Geert's patch implements a mechanism in the ti-sn65dsi86 driver to > > handle this, and assign an id managed by the parent. In a sense we could > > consider this to be similar to what is done for I2C, where the bus > > number is also a property of the parent. However, the big difference is > > that the I2C bus number is managed by the I2C subsystem, while here the > > id is managed by the ti-sn65dsi86 driver, not by the auxiliary device > > core. This would require duplicating the same mechanism in every single > > driver creating auxiliary devices. This strikes me as a fairly bad idea. > > The problem should be solved by the core, not by individual drivers. > > The "id" is just a unique number, it is "managed" by the thing that is > creating the devices themselves, not the aux core code. I don't see why > the i2c bus number has to match the same number that the ti driver > creates, it could be anything, as long as it doesn't match anything else > currently created by that driver. Laurent does not say it has to match the i2c bus number. He does think the auxilliary bus should provide a mechanism to allocate these IDs (e.g. usin g AUX_DEVID_AUTO?). However, using i2c_client->adapter->nr instead of ida_alloc() in the TI driver does sound like a good idea to me... > If we had the aux core code create the id, it would just use a unique > counter, and that would not reflect any mapping to anything, so I don't > see how that is any different here. And then we would get something like: /sys/bus/auxiliary/devices ├── ti_sn65dsi86.gpio.0 ├── ti_sn65dsi86.pwm.1 ├── ti_sn65dsi86.aux.2 ├── ti_sn65dsi86.bridge.3 ├── ti_sn65dsi86.gpio.4 ├── ti_sn65dsi86.pwm.5 ├── ti_sn65dsi86.aux.6 └── ti_sn65dsi86.bridge.7 Which is similar to the first approach I tried (calling ida_alloc() in ti_sn65dsi86_add_aux_device() instead of ti_sn65dsi86_probe()). Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
