On Thu, 19 Feb 2009, Wolfgang Denk wrote: > Dear k...@koi8.net, > > In message <pine.lnx.4.64ksi.0902191141090.18...@home-gw.koi8.net> you wrote: > > > > > in board config file ... OK, we are worser against your approach, because > > > we have for all I2C_SDA, I2C_SCL accesses + 1 switch, but I don;t think > > > this is such a problem. > > > > First of all, you are using an external global variable for object methods. > > That is a VERY BAD practice and I can't even imagine a use case that would > > justify this. > > We are pretty pragmatic here. If it solves a problem efficiently, we > use even global variables.
But not in object methods... And it must serve some purpose. I'm a sinner myself and I have to confess to even using goto's sometimes but it must have some reason... > > That means you'll have to rewrite the entire U-Boot. 99% of the boards have > > only one bus so they did not switch busses. That means they never called > > that i2c_set_bus_num() relying on i2c_init() in libxxx/board.c instead. > > I cannot follow your argument. > > Yes, the status quo is as you describe, it relies on i2c_init() and > is simple-minded and does not support an arbitry number of > arbitrarily complex I2C bus trees and multiplexors and expanders and > what else. But it was sufficient for the first 10 years and 500 > boards of U-Boot development. > > Now we are discussion a major redesign, so what is the big problem of > changing this part? "rewrite the entire U-Boot"? Please stay serious. > Compared to the other changes you suggest, this is not that big a > part. No, my changes are limited. Look, somebody must initialize an adapter. As for now it is done with a single i2c_init() usually in libxxx/board.c. Then the entire code assumes adapter is already initialized and just issues i2c_read/write() as it see fits. 99% of this code is written on assumption that there is only one I2C bus so it doesn't use i2c_set_bus_num() or whatever, it just fires up i2c_read() and that's it. This would perfectly work with my changes without modifying that code -- the only bus is bus number 0 so there is nothing wrong with not setting the bus for each I2C access; it is already at that only bus. Now, if we have adapter initialization moved to i2c_set_bus() all that code will cease to work because i2c_set_bus() is never called thus adapter will never be initialized and all those i2c_read() and friends will fail. That means that we should read through each and every board's code to find where i2c functions are used and add i2c_set_bus() calls as needed. That is not INSTEAD of that big rewrite, that is _IN ADDITION_ to it. That is a very sizeable chunk of additional changes. I DID think of adding adapter initialization to i2c_set_bus() initially but then it turned out it generated more problems than it solved (and it solved none) so I dropped that idea. > > Sorry guys, I do not have THAT much free time that my employer would let me > > to spend on this. > > Well, you at least have some commercial motivation to spend time for > this code and discussion, while for me it's all my "free" time (and I > better don't tell you what my wife says of my interpretation "free" > here). Eh, you won't believe what constitutes my "free" time and for how long ahead that "free" time is planned out. I don't think mere mortals live that long... :) --- ****************************************************************** * k...@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * ****************************************************************** _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
