QVGA for Neo

john cass johnpcass at yahoo.com
Fri Sep 28 12:48:37 CEST 2007

Hello Andrej - thanks for your comments - regarding the connection between
the LCDC (framebuffer) and the LCM for a "video mode change" :

>>2) What's the best way to send a command from the framebuffer driver to the LCM 
>>    (spi) module - so that we can have a full change of mode using e.g. fbset?
>>    The way the code is currently structured, a call to the mode change function
>>    in the LCM module needs a data structure which the framebuffer doesnt know 
>>    about. (e.g. should we store a reference to the jbt_info structure 
>>    statically in jbt6k74.c so that external callers dont need to specify it?
>>    or should we try to arrange a call through the sysfs user interface?)

> I think the jbt6k74 should export these properties through sysfs as it
> is a separate device from the LCDC.

Andrej - jbt6k74 does already export these to sysfs.  The question is whether that
is the best way for the kernel to access its functions internally : 
(How) can one access the sysfs from within the kernel?  Is there a kernel interface?
Do we have to pass a message out to a user application which can access sysfs?
This last sounds like a nasty way of doing things..
It would be easy (and reasonable for the gta01) to assume there is only one jbt6k74
device and keep a data structure statically in jbt6k74.c.  This would allow jbt6k74.c 
to EXPORT a kernel function for changing mode which would be fast and easy.


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