On Tue, Sep 08, 2015 at 09:48:48AM +0200, Hans de Goede wrote: > Hi, > > On 07-09-15 22:52, Maxime Ripard wrote: > >Hi, > > > >On Mon, Sep 07, 2015 at 11:30:03AM +0200, Hans de Goede wrote: > >>>>>bma250 already has devicetree support. It is used in Gemei G9 > >>>>>tablet (sun4i-gemei-g9.dts). > >>>> > >>>>Yes I've seen that, but does it actually work? I've not tried but > >>>>I do not see any compatible string in the actual bma250 code in > >>>>the kernel, so I believe that this part of the sun4i-gemei-g9.dts > >>>>file does not work ? > >>> > >>>It worked (even without IRQs) when I submitted the patch. Driver > >>>itself is under iio/accel/bma180.c > >> > >>That is really weird, because: > >> > >>https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/iio/accel/bma180.c > >> > >>Does not have an of_match_table ... ?? > > > >Not really, when using DT, i2c will set the i2c_client name to the > >device part of the compatible [1] [2], and then if the of_device_id > >lookup fails, will fallback to matching the i2c_client name to the > >i2c_device_id [3]. Which in our case matches. > > > >Maxime > > > >[1] http://lxr.free-electrons.com/source/drivers/i2c/i2c-core.c#L1281 > >[2] http://lxr.free-electrons.com/source/drivers/i2c/i2c-core.c#L969 > >[3] http://lxr.free-electrons.com/source/drivers/i2c/i2c-core.c#L461 > > Hmm, not sure whether that is a useful feature or an ugly hack :) Don't shoot the messenger :) But I don't know either. > It is sorta unexpected either way. But I can make good use of this to > enable the accelerometer and maybe also some touchscreens on a bunch of > boards I have. > > Still should we rely on this? This means relying on Linux kernel behavior, > rather then something documented in Documentation/devicetree/bindings/... AFAIK, the behaviour isn't going away, there's been a few patches to remove the need for i2c_device_id, and they've all been nacked, so I'd say we can use it as is. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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