Hello ksi,
ksi@koi8.net wrote:
On Thu, 19 Feb 2009, Heiko Schocher wrote:
Hello ksi,
ksi@koi8.net wrote:
On Wed, 18 Feb 2009, Heiko Schocher wrote:
Hello Wolfgang,
Wolfgang Denk wrote:
Dear ksi@koi8.net,
In message Pine.LNX.4.64ksi.0902171233390.30435@home-gw.koi8.net you wrote:
[...]
> What makes you insist that we cannot change a variable if we need to > be able to change one? It is NOT just variable. My approach uses i2c _BUS_, not _ADAPTER_. And number of busses can be bigger than number of adapters (e.g. when some busses a reached via muxes or switches.) When doing i2c_set_current_bus() you are switching _NOT_ adapters, but busses. That involves not only changing that global variable but also reprogramming muxes/switches for i2c_set_current_bus() to be consistent and hardware independent. Otherwise your code should know if that particular bus it is switching to is directly connected or switched and check the bus it is switching from for muxes. If they are switched, your code should disconnect the current bus switches, then do that i2c_set_current_bus() and connect the switches to the new bus after that.
That means that code MUST somehow know the topology to take appropriate actions and properly configure those switches. That means you should somehow describe that topology for each and every board in CONFIG_* terms and make each and every place at U-Boot that invokes _ANY_ i2c function to take care of that switching.
You convinced me. This code must not be used before relocation to RAM, then.
But is is possible to use that code when running from flash, if this current pointer is writeable ...
It is not the pointer that must be writeable, it's what it is pointing to...
But in your approach this is also not writeable! So we lost nothing, when using such a pointer.
No, we did NOT. I can still cal adap[N]->init() and it will init the proper
For what you will do this, when you can;t use the adapter, when running from flash? See Later, why you cannot use it.
adapter. It does NOT require any global variables for it, it is self-sufficient.
But you could not switch busses, nor work with it, first because i2c_set_bus_num() don;t work for you and i2c_cur_bus is not writeable, so _all_ accesses with the API in i2c-core.c like for example
int i2c_read(u_int8_t chip, unsigned int addr, int alen, u_int8_t *buffer, int len) { return(ADAP(i2c_cur_bus)->read(chip, addr, alen, buffer, len)); }
_will_ fail, when running from flash, because i2c_cur_bus is not writeable!
So why will you initialize all adapters when running from flash?
But this is no problem, when we make i2c_cur_bus or this pointer I would like to see, writeable. And think about my proposal for i2c_set_bus_num() and we have there also no problem with calling init() for an adapter.
bye Heiko