• Paul Burton's avatar
    auxdisplay: img-ascii-lcd: driver for simple ASCII LCD displays · 0cad855f
    Paul Burton authored
    Add a driver for simple ASCII LCD displays found on the MIPS Boston,
    Malta & SEAD3 development boards. The Boston display is an independent
    memory mapped device with a simple memory mapped 8 byte register space
    containing the 8 ASCII characters to display. The Malta display is
    exposed as part of the Malta board registers, and provides 8 registers
    each of which corresponds to one of the ASCII characters to display. The
    SEAD3 display is slightly more complex, exposing an interface to an
    S6A0069 LCD controller via registers provided by the boards CPLD.
    However although the displays differ in their register interface, we
    require similar functionality on each board so abstracting away the
    differences within a single driver allows us to share a significant
    amount of code & ensure consistent behaviour.
    
    The driver displays the Linux kernel version as the default message, but
    allows the message to be changed via a character device. Messages longer
    then the number of characters that the display can show will scroll.
    
    This provides different behaviour to the existing LCD display code for
    the MIPS Malta or MIPS SEAD3 platforms in the following ways:
    
      - The default string to display is not "LINUX ON MALTA" or "LINUX ON
        SEAD3" but "Linux" followed by the version number of the kernel
        (UTS_RELEASE).
    
      - Since that string tends to be significantly longer it scrolls twice
        as fast, moving every 500ms rather than every 1s.
    
      - The LCD won't be updated until the driver is probed, so it doesn't
        provide the early "LINUX" string.
    Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
    Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
    Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
    Cc: Guenter Roeck <linux@roeck-us.net>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Geert Uytterhoeven <geert@linux-m68k.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: linux-mips@linux-mips.org
    Cc: linux-kernel@vger.kernel.org
    Patchwork: https://patchwork.linux-mips.org/patch/14062/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    0cad855f
img-ascii-lcd.c 10.6 KB