Re: [PATCH 08/32] dmaengine: ste_dma40: Optimise local MAX() macro

From: Linus Walleij
Date: Thu Apr 25 2013 - 04:36:32 EST

On Thu, Apr 18, 2013 at 12:11 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote:

> The current implementation of the DMA40's local MAX() macro evaluates
> its arguments more times than is necessary. This patch strips it
> optimises it to only evaluate what's appropriate.
> Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
> Cc: Dan Williams <djbw@xxxxxx>
> Cc: Per Forlin <per.forlin@xxxxxxxxxxxxxx>
> Cc: Rabin Vincent <rabin@xxxxxx>
> Reported-by: Harvey Harrison <harvey.harrison@xxxxxxxxx>
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> -#define MAX(a, b) (((a) < (b)) ? (b) : (a))
> +#define MAX(a, b) ((a > b) ? a : b)

Much has been said about this patch already, but notice what it is
used for instead, one single thing at compile-time:

struct d40_base {
reg_val_backup_v4[MAX(BACKUP_REGS_SZ_V4A, BACKUP_REGS_SZ_V4B)];

i.e. defining the size of that array at compile-time.

The actual size is figured out in d40_hw_detect_init().

So what about you just devm_kmalloc() that array instead and
delete this macro. That is the real fix.

Linus Walleij
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at