Generic get_something from an i2c_client

[Marc Gonzalez <marc.w.gonzalez@free.fr>]

Hello,

In media drivers, TS drivers typically hard-code their front-end (demod and tuner)
init by loading the modules themselves.

I feel this is not a good solution for SoCs, where the TS HW might be on the SoC,
and the front-end be on the board. So we may have different front-ends for
different boards, and the driver would have to hard-code all of them.

Am I making sense?

Here's an example of what I mean:
https://elixir.bootlin.com/linux/latest/source/drivers/media/usb/dvb-usb-v2/dvbsky.c#L466

I've been working on defining the demod in DT, and having a phandle
to the demod in the TSIF node.

I've got everything working like I had hoped, but I have many ugly hacks.

The TSIF driver needs to register the frontend, which is created in
the demod driver.

So I have:

	struct device_node *toto = of_parse_phandle(np, "demod", 0);
	if (!toto) panic("of_parse_phandle");
	struct i2c_client *demod = of_find_i2c_device_by_node(toto);
	if (!demod) panic("of_find_i2c_device_by_node");
	printk("\tdemod=%px\n", demod);
	struct dvb_frontend *get_fe(struct i2c_client *client);
	my_dvb_frontend = get_fe(demod);

The problem is get_fe(). It needs to be a call-back, so that every
demod can implement his own version. But only a few i2c_client's
have a dvb_frontend to return.

Could we have a generic void *get_something() callback in struct i2c_client?
(Seems like the wrong place)

How can I solve this conundrum?

Maybe look above i2c, in struct device?

Regards.