Re: i2c: introduce i2c helper i2c_find_client_by_name()

[Bin Gao]

On 6/19/2013 3:13 AM, Wolfram Sang wrote:
> > Even you prefer to extend v4l2, you still need this helper.
> > The idea is just to move the unregister/register from a specific ISP driver
> > to v4l2.
> >
> > I think you misunderstood my pionts somehow. Let me clarfiy a little bit:
> >
> > Current solution:
> > 1. Platform codes(on top of DT/ACPI5/SFI) don't call i2c_register_board_info(),
> > instead, prepare a table(kind of platform data) that has all camera i2c device information.
> > 2. ISP driver registers devices listed in the table to i2c core - this makes sure
> > v4l2 takes over these devices.
> > The problem with this solution is that when a camera device runs on both ACPI5 and
> > SFI, the platform codes will get a bit complicated and it's difficult to ensure one
> > binary kernel runs on both platforms(ACPI5 and SFI).
> > (To extend v4l2 with this solution doen't resolve my problem)
> >
> > Solution I'm suggesting:
> > 1. Let the platform codes call i2c_register_board_info() anyway.
> > 2. Since ISP driver knows which camera devices it supports, so it simply unregisters
> > those devices (get the client by the introduced helper), then register it within v4l2.
> > This solution ensure one binary kernel can run on both platforms.
> > (To extend v4l2 with this solution could not be feasible, the device table is
> > ISP driver specific, not v4l2 specific)
>
> I also wonder about the need to unregister. I have to admit I don't know
> much about I2C handling in v4l2. But if it requires unregistering from
> i2c core and registering to v4l2 core, then it sounds to me like we
> could check if there is a more fundamential cleanup needed? Deferring
> for now, looks like an issue worth looking at, yet there are other
> things in the queue first.

Platform codes are supposed to call i2c_register_board_info() or 
i2c_new_device() to register devices, we don't want to change this.
Not sure v4l2 can still take over the devices without 
unregistering/registering. Need look deeply into the v4l2 code...

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