Hi, Andy Green <andy at warmcat.com> writes: > A whole other way forward is to consider to replace the EEPROM from > the original proposal (which does provide its own advantages such as > simplicity, I accept) with something else that ends up on another > PC. In this concept some logic presents a fake I2C peripheral to the > DDC interface at an I2C address of our choosing. This logic acts as a > bidirectional "UART" type of thing, allowing transfer of data in both > directions between the Linux box being debugged and another PC. Right. I think one could use something like ATMEL 89F2051 (20-pin 8051 non-SMD clones with flash and hardware UART) or something similar. Client I2C is difficult in Linux (using general purpose I/O port) but with a dedicated CPU it's not a problem (not sure about 400 kHz access). > http://warmcat.com/milksop/filtror.html Well, that's a bit more complicated. I'm not going to try that on an experimental PCB :-) > However this would be much simpler, not even needing RAM. It can hook > to the second PC by the same I2C method, parallel printer port, RS232 > or USB depending on the level of complexity of the design. > > I guess the link will feel quite like a 9600 or 19200 baud serial port > in terms of throughput. Depends on I2C. With something like 400 kHz it should be faster, probably like 115200. > Maybe this effort is considered too esoteric, but it seems to me to be > a reason to keep the DDC access drivers standalone, the > hardware-specific framebuffer drivers can call through to them and we > can use them in a clean way. I realize this is a bit of a late > objection and that there was not previously much point to keeping them > as separate things in the world. Actually we have: - the Xserver "hardware access" issue - DRI/DRM - now the I2C bus driver - frame buffer To avoid conflicts we really need them managed by a single driver. Probably the GGI (KGI?) should be revisited? Long-term project, unfortunatelly, but I think we'll have to do that eventually. The I2C, graphics subsystem and DRI/DRM could be sub-modules, with the master module only keeping track of hardware access, mode settings etc. -- Krzysztof Halasa
