Hi Alexander, On Wed, 22 Aug 2012 09:57:07 +0200 Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx> wrote: > Hello, > > On Wednesday 22 August 2012 15:29:18, Feng Tang wrote: > > On Wed, 22 Aug 2012 08:30:35 +0200 > > Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > Hello, > > > > > > I just noticed the 3.4 linux kernel fails to sucessfully probe the i2c-eg20t > > > driver. I returns with EBUSY error. It worked on the 3.0 kernel. To my view it > > > is caused the commit 07e8a51ff68353e01d795cceafbac9f54c49132b ( i2c-eg20t: use > > > i2c_add_numbered_adapter to get a fixed bus number). > > > The reason it actually fails is that the i2c-isch driver is registered > > > beforehand which gets bus number 0. But this one is the bus number the eg20t > > > driver wants to register. > > > > Make sense. > > > > > A possibility is that if i2c_add_numbered_adapter failed with EBUSY just use > > > i2c_add_adapter to get at least the driver working, but with a non-fixed bus > > > number. Opinions? > > > > Or can we give it a fixed offset, like let the i2c_eg20t controller bus number > > start with 4? I don't expect there will be more than 4 other i2c controllers > > on EG20T compatible platforms. > > Why use a fixed one? Give the driver (and maybe every i2c bus driver) a parameter which sets the base bus number it should use. > E.g. i2c-eg20t.base-bus-num=2 so it will register the bus numbers starting from 2. If this parameter is unset. It would use the first free one, thus simply using i2c_add_adapter. The reason we need a fixed number is it is easier for platform code which needs to register dozens of i2c devices to different controllers with i2c_register_board_info, and they need provide a bus number for each i2c device, this _binding_ info is not detectable but have to be fixed. Yes, your module parameter "base-bus-num" sounds like a plan too, at the cost of some extra setting in the kernel cmdline. And I'm fine with all solutions as long as I can get a _fixed_ bus number so that I can easily write the platform config code (I guess this is same for device tree, and even ACPI 5.0) Thanks, Feng -- 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
