Re: [Lcd-linux] lcd over gpio

[Mattia Jona-L. <mat...@gm...>]

On Tue, Jan 18, 2011 at 1:12 PM, Claudio <cla...@gm...> wrote:
> Dear mattia,
> let me introduce a different scenario.
>
> The USB device are really different each other and support for its
> could be difficult and inefficient, beside on embedded devices
> generally you want to use the USB port for something more useful.

Hmmmm, quite a lot of people might disagree with you as USB is now
considered THE universal and preferred way to connect external devices
to computers. Anyway, I see your point.

> The gpio implementaion instread allow you to support a huge range of
> embedded devices like router, develop board as well some routerboard
> or industial board; moreover you can use a USB to GPIO adapter (like
> ftdi) and then connect any kind of lcd also on you modern laptop/pc
> (that typically don't have parport or gpio).

I agree and this should in principle be very easy. If the GPIO
implementation in the kernel is at a usable level then I'm more than
happy to try to use it. In any case it will provide a sort of standard
way to access the display. If this is the case then it is very easy as
the only two functions in the HD44780 driver that need a rewrite are
the two lowlevel read and write functions. If I write a patch, will
you be able to test it and report on it?

> The parport implementation is hacky and should be mainained just for
> history but it is de facto obsolete(how many device you can found with
> parport today in your home?).

I agree and that's why I wanted to move to something newer. LCD-Linux
was intended at the beginning to provide a cheap display output to old
and obsolete hardware. These days this goal does not make any sense as
an embedded device can run as a router much more efficiently than an
old computer.

> In this scenario the GPIO support is priority and such version of
> lcd-linux is, in imho, also more acceptable by mainline kernel.

LCD-Linux was already proposed for inclusion in the kernel mainline
but some issues prevented this. The main reason being that LCD-Linux
duplicates in some sense the console emulation and kernel developers
don't like duplicate code (why reinventing the wheel?). To make a long
story short LCD-Linux wasn't rejected but it was asked to merge some
parts of it with the existing kernel code, which is not always easy.
There was some traffic about this on the main linux kernel maling list
in july 2010.

Best

Mattia


>
> Best regards
>