[PATCH 2/2] bootcount: Add driver model I2C driver

[Simon Glass]

Hi Philip,

On Tue, 17 Oct 2023 at 06:57, Philip Oberfichtner <pro at denx.de> wrote:
>
> Hi Simon,
>
> maybe you can give me a hint on how to implement this cleanly in driver
> model?
>
> To sum it up, I'd like to have a phandle pointing to *any* I2C device,
> not knowing which UCLASS actually fits. Then the device and the parent
> bus should be probed/prepared such that dm_i2c_read() can be used.
>
> Any ideas on this?

I suggest a phandle to the i2c device.

You can use oftree_get_by_phandle() to get the node and then
device_find_global_by_ofnode() to get the device.

This is expensive, although eventually I suspect we will fix that with
OF_LIVE. I think it should be implemented as a new function in i2c.h
so we can change the impl later easily.

If you want to be more efficient you could do something like:

int phandle = ??

struct uclass *uc;
struct udevice *bus;

uclass_id_foreach_dev(UCLASS_I2C, bus, uc) {
   struct udevice *dev;

   device_foreach_child(dev, bus) {
      if (!dev_read_u32(dev, "phandle", &val) && val == phandle)
         return dev;
   }
}

but honestly now I look at it, that is awful. We try to avoid exposing
the internals of phandle because it allows us to (one day) maintain a
list of them.

[..]

Regards,
Simon