Re: [PATCH] Staging: fbtft: Do not use same argument more than once in bit operation.

[Alison Schofield <amsfield22@gmail.com>]

The reason may be that author is trying to
to explicitly reflect the register settings.

Considering this code...

static int init_display(struct fbtft_par *par)
{
.................snip........................

	/* Set temperature compensation */
        write_reg(par, 0x24 | (temp & 0x03));

        /* Set panel loading */
        write_reg(par, 0x28 | (load & 0x03));

        /* Set pump control */
        write_reg(par, 0x2C | (pump & 0x03));

        /* Set inverse display */
        write_reg(par, 0xA6 | (0x01 & 0x01));

        /* Set 4-bit grayscale mode */
        write_reg(par, 0xD0 | (0x02 & 0x03));

In the first 3 commands temp,load,pump are vars &'d with a mask.
In the last 2 commands 0x01 and 0x02 are hardcoded values &'d with a mask.
Sometimes that hardcoded value just happens to be the same as its mask.
I might even guess that this author knew it was redundant, but
that the compiler would reduce all of that for him anyway.

you can see the register definitions here if you want to get to
very bottom of this ;)
http://lcdhype.condense.de/index.php?act=Attach&type=post&id=6112&index=0

I wonder if it is better to define all those hardcode values for even
more clarity.