[PATCH] MTD: fix dataflash 64-bit divisions

[Nicolas Pitre]

On Wed, 17 Dec 2008, Artem Bityutskiy wrote:

> -	if ((instr->addr + instr->len) > mtd->size
> -			|| (instr->len % priv->page_size) != 0
> -			|| (instr->addr % priv->page_size) != 0)
> +	if (instr->addr + instr->len > mtd->size)
> +		return -EINVAL;
> +	tmp = instr->len;
> +	if (do_div(tmp, priv->page_size))
> +		return -EINVAL;
> +	tmp = instr->addr;
> +	if (do_div(tmp, priv->page_size))
>  		return -EINVAL;

Is it possible to have priv->page_size not a power of two?  If no then 
the above test is becoming rather costly, and something like:

	if ((instr->len | instr->addr) & (priv->page_size - 1))
		return -EINVAL;

would be much cheaper.

> -		pageaddr = instr->addr / priv->page_size;
> +		tmp = instr->len;
> +		do_div(tmp, priv->page_size);
> +		pageaddr = tmp;

Here I suggest you include <linux/math64.h> and use this instead:

	pageaddr = div_u64(instr->addr, priv->page_size);


Nicolas