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. > 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. > 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. > 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 > keypad connection? I can find out from the code, but I have not yet > seen the keypad code. It used to be documented as an ASCII-art diagram but I can't find that anymore :-/ IIRC you had to wire buttons between some of the outputs and some of the inputs. From what I remember, it was possible to detect that an input is : - tied to ground - tied to a data line - tied to a control line I found this comment in the old source file : "document 24 keys keyboard (3 rows of 8 cols, 32 diodes + 2 inputs)" So maybe we only use data lines and not control lines. And the keypad code periodically scans all outputs and notes inputs states. The Nexcom profile works with the keypad, though I don't have the wiring in mind. It uses 4 keys. It should be easy to find that from the code though. Hmmm I found an old description of 2001 (kernel 2.2.18) from the one of the first circuit I made (with a serial lcd). It involved the smartcard detector (now removed) and 6 keys : strobe -> lcd.strobe d0 -> lcd.serial.din (serial) + lcd.parallel.d0 + keypad.k0 d1 -> d7 => lcd.parallel.d1-d7 + keypad.k1-k7 ack <- smartcard.dout busy <- pe <- (keypad common1 if more than 8 keys) select <- keypad common0 autofeed -> lcd.serial.backlight / lcd.parallel.rs error <- smartcard.detector 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
