Re: Coding style details (checkpatch)

Krzysztof Hałasa
2015-06-22T06:39:04Z

Joe Perches <joe@perches.com> writes:

> It might be better to use some base + index macro
> as it could be smaller object code.
>
> Something like:
>
> #define REG_NO(base, multiplier, index) (base + (multiplier * index))
>
> reg_write(vc->dev, REG_NO(0x10, 1, vc->ch), dma_cfg);
> or
>
> #define VDMA_CHANNEL_CONFIG 0x10
>
> reg_write(vc->dev, REG_NO(VDMA_CHANNEL_CONFIG, 1, vc->ch), dma_cfg);

Wouldn't work, the register map is a bit messy.
E.g.

#define DMA_PAGE_TABLE0_ADDR ((const u16[8]){0x08, 0xD0, 0xD2, 0xD4, 0xD6, 0xD8, 0xDA, 0xDC})
#define DMA_PAGE_TABLE1_ADDR ((const u16[8]){0x09, 0xD1, 0xD3, 0xD5, 0xD7, 0xD9, 0xDB, 0xDD})

also

#define VDREG8(a0) ((const u16[8]){ \
a0 + 0x000, a0 + 0x010, a0 +0x020, a0 + 0x030, \
a0 + 0x100, a0 + 0x110, a0 +0x120, a0 + 0x130})
#define VIDSTAT VDREG8(0x100)
#define BRIGHT VDREG8(0x101)
#define CONTRAST VDREG8(0x102)

etc.

One would have to remember (writing .c code) which scheme applies to
which access. The tables, while probably less than optimal WRT CPU
cycles used, are consistent, and the addressing details are grouped in
one place - the *regs.h file.