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auxdisplay: charlcd: Add support for 4-bit interfaces

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In 4-bit mode, 8-bit commands and data are written using two raw writes
to the data interface: high nibble first, low nibble last.  This must be
handled by the low-level driver.

However, as we don't know in which mode (4-bit or 8-bit) nor 4-bit phase
the LCD was left, initialization must always be handled using raw
writes, and needs to configure the LCD for 8-bit mode first.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Geert Uytterhoeven 2017-03-10 15:15:18 +01:00 • committed by Greg Kroah-Hartman
parent 39f8ea4672
commit ac201479cc
2 changed files with 32 additions and 6 deletions
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2
include/misc/charlcd.h
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@ -14,6 +14,7 @@ struct charlcd {
const struct charlcd_ops *ops;
const unsigned char *char_conv; /* Optional */
int ifwidth; /* 4-bit or 8-bit (default) */
int height;
int width;
int bwidth; /* Default set by charlcd_alloc() */
@ -28,6 +29,7 @@ struct charlcd_ops {
void (*write_data)(struct charlcd *lcd, int data);
/* Optional */
void (*write_cmd_raw4)(struct charlcd *lcd, int cmd); /* 4-bit only */
void (*clear_fast)(struct charlcd *lcd);
void (*backlight)(struct charlcd *lcd, int on);
};