Date:	Sat, 6 Dec 2014 11:28:54 +0100
From:	Mariusz Gorski <marius.gorski@...il.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Willy Tarreau <w@....eu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: staging: panel: suggestions needed

Hi Supid,

On Sat, Dec 06, 2014 at 03:39:33PM +0530, Sudip Mukherjee wrote:
> On Sat, Dec 06, 2014 at 09:41:08AM +0100, Willy Tarreau wrote:
> > Hi Sudip,
> > 
> > [ CCing Mariusz who's currently cleaning up the driver ]
> > 
> > On Tue, Dec 02, 2014 at 01:32:14PM +0530, Sudip Mukherjee wrote:
> > > Hi,
> > > I have been looking at your panel driver, and am attaching a 20x4 alphanueric
> > > lcd to it. Will start testing it in a few days as and when I get time. Looks
> > > like, it is receiving mostly checkpatch and sparse cleanups.
> > 
> > yes mostly.
> > 
> > > Just wanted your opinion on few things I was thinking:
> > > 	1) Number of lines you have fixed to 2 and 40 char per line. since I am
> > > 	going to connect 20x4 , i need to remember that after displaying 20
> > > 	character in 1st line, next char will come to 3rd line. instead why
> > > 	don't we make the option of number of line to 4 ?
> > 
> > Feel free to do so. I never had the luck to own a 4-line LCD so this
> > was never even planned. And yes, I remember something about 4-line LCDs
> > using tricks such as 2x40 addressing being split into 4x20.
> well, i work in a company which is in embedded training, so i have access to few hardware, and for this i can have 16x2 and 20x4 lcd, but no serial lcd ... :(

Setting the height to 4 is not going to make it work properly - due to
the way the display is working internally. I also own one in 4x20 size
and after I get done with the cleaning stuff, I'm going to add proper
support for it.

> > 
> > > 	2) The lcd commands you are writing to the lcd in an escape sequence
> > > 	while writing to the lcd. Instead of that why don't we use ioctl for
> > > 	lcd commands, and writing to the device will involve only sending data
> > > 	to lcd ?
> > 
> > Because you cannot send that from a script. It's just as if you had to use
> > an ioctl to clear your terminal, inverse its video or to move its cursor,
> > it would not be very convenient.
> yes, ioctl will not be possible from script. but here in India, we will usually use c code for embedded systems, on very rare occassion we will use scripts. and we will be using open(), read(), write(), ioctl() and close() system calls from our projects.
> here, we can have both methods in the code. if someone is using escape sequence - that will work, and we can also have the ioctl for the same purpose.
> > 
> > > 	3) You have given fixed minor number in your code. Any problem if we
> > > 	make it dynamic ?
> > 
> > No objection, but I think we should keep a config option to bind to the
> > old minor. The rationale behind this is that this driver is mostly used
> > in embedded systems with a fixed /dev.
> ok. but one doubt: won't misc_register create the /dev entry automatically ?
> 
> thanks
> sudip
> > 
> > > 	4) For now I am only attaching a LCD, but I also want to attach a
> > > 	keypad to it. Can you please let me know about the schematic of the
> <snip>
> > init -> 
> > select_in ->
> > 
> > And here's the module load command I used to run :
> > insmod /tmp/panel-0.8.0.o parport=0 lcd_enabled=2 keypad_enabled=1 lcd_width=16 lcd_hwidth=16 lcd_height=2
> > 
> > Hoping this helps,
> > Willy
> > 
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