On Thu, Jun 5, 2014 at 4:55 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > On Thu, 05 Jun 2014, Grant Likely wrote: >> On Thu, Jun 5, 2014 at 11:37 AM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> > On Thu, 05 Jun 2014, Grant Likely wrote: >> > >> >> On Wed, 4 Jun 2014 13:09:56 +0100, Lee Jones <lee.jones@xxxxxxxxxx> wrote: >> >> > Currently this is a helper function for the I2C subsystem to aid the >> >> > matching of non-standard compatible strings and devices which use DT >> >> > and/or ACPI, but do not supply any nodes (see: [1] Method 4). However, >> >> > it has been made more generic as it can be used to only make one call >> >> > for drivers which support any mixture of OF, ACPI and/or I2C matching. >> >> > >> >> > The initial aim is for of_match_device() to be replaced by this call >> >> > in all I2C device drivers. >> >> > >> >> > [1] Documentation/i2c/instantiating-devices >> >> > >> >> > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> >> >> >> >> I don't like this. It drops all type safety on the match entry >> >> and the caller has no idea what it got back. >> > >> > Okay, so what's the best way forward? >> > >> > Introduce a i2c_of_match_device() call instead? >> >> I still think the way to do it is to emulate the missing i2c_device_id >> when calling the drivers .probe() hook by having a temporary copy on >> the stack and filling it with data from the OF or ACPI table.... > > That's the opposite of what I'm trying to achieve. I'm trying to get > rid of unused i2c_device_id tables, rather than reinforce their > mandatory existence. I think an i2c_of_match_device() with knowledge > of how to match via pure DT principles (of_node/compatible) and a > fall-back, which is able to match on a provided of_device_id table > alone i.e. without the requirement of an existing of_node. What I'm suggesting does allow all those tables to be removed, but without a painful API breakage... having said that, it is only the drivers that drop their i2c_device_id tables that need to support the fallback behaviour, so it would be fine to pass null into the i2c_device_id argument and make the driver call the new function that returns an of_device_id regardless of whether a node is attached. > I've also been mulling over the idea of removing the second probe() > parameter, as suggested by Wolfram. However, this has quite deep > ramifications which would require a great deal of driver adaptions. That is of course the ideal. It would be a lot of work (I count 633 users), but it would get i2c exactly where you want it to be. I did that kind of work when I merge platform_bus_type with of_platform_bus_type. You can mitigate it though by creating a .probe2 hook that doesn't have the parameter and then change over all the users in separate commits, finally removing the old hook when safe to do so. g. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
