On Fri, 12 Sep 2014, Javier Martinez Canillas wrote: > [adding Sjoerd as cc who was the one that raised the module auto-loading issue] > > Hello, > > On Fri, Sep 12, 2014 at 3:46 PM, Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote: > >> > >> Placing this firmly back on your plate. I truly hope we don't miss > >> another merge-window. This patch-set has the support of some pretty > >> senior kernel maintainers, so I hope acceptance shouldn't be too > >> difficult. > >> > >> As previously discussed I believe it should be okay for an I2C device > >> driver _not_ supply an I2C ID table to match to. The I2C subsystem > >> should be able to match via other means, such as via OF tables. The > >> blocking factor during our previous conversation was to keep > >> registering via sysfs up and running. This set does that. > > > > As mentioned in another thread, modaliases are one other possible side > > effect. As Javier correctly mentions, the beaviour does not really > > change with your patchset. Yet, if we remove i2c_device_id from drivers > > too carelessly, they might not be bound anymore. > > > > Right, removing the I2C ID table even from drivers that don't really > need it (e.g: IP blocks only present in DT platforms) will as you said > break module auto-loading. Probing will work since the OF table is > used to match the device in i2c_device_match() but is the I2C table > what is used to fill the valid module aliases with the current > behavior of i2c_device_uevent(), the aliases filled from the OF table > are never used. > > So what I propose is to do it incrementally: > > 1) Merge Lee's series since that is definitely a step in the right > direction to not make an I2C table mandatory (still will be needed for > module auto loading though). > > 2) On a follow-up series, make sure that all I2C drivers have a proper > OF table and that are using the MODULE_DEVICE_TABLE(of,...) macro to > fill the of:<foo> module aliases. That way the modules will have the > proper aliases of the form "of:<foo>" besides the "i2c:<foo>" one. > (even when always i2c:<foo> is reported to user-space currently). > > 3) Apply the patch I posted [0] that changes the behavior of > i2c_device_uevent() to report the OF uevent env vars to user-space in > case of DT probing which after 2) should not regress any driver module > auto-loading since all drivers should fill the of:<foo> aliases. This sounds resonable. > After this, DT-only drivers will only need an OF table and legacy > drivers will only need an I2C table. Drivers that support both will > still need the two tables though which is a drawback of this approach > since unnecessary duplication will exist on these drivers and can > cause issues when both tables are not in sync as we saw on the issue > reported by Sjoerd on [1]. > > So an alternate approach could be to do the opposite, just remove the > OF tables entirely from the I2C drivers and only use the I2C table > even for DT-only drivers. This is possible since i2c_device_match() > will succeed even without an OF table because i2c_match_id() matches > for compatible strings and what is reported as uevent is what is in > the I2C table anyways. I believe that is what Sjoerd suggested but > I'll let him comment on that in case I misunderstood. This would be really bad. It would go completely against what I have working to achieve and OF conventions. > By the way, the SPI subsystem has the same behavior, I raised the issue on [2]. > > Best regards, > Javier > > [0]: https://lkml.org/lkml/2014/9/11/269 > [1]: https://lkml.org/lkml/2014/9/9/100 > [2]: https://lkml.org/lkml/2014/9/11/458 -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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
