[U-Boot] [PATCH] NAND: Allow per-buffer allocation

[Scott Wood]

On 08/09/2011 04:54 PM, Marek Vasut wrote:
> Don't allocate NAND buffers as one block, but allocate them separately. This
> allows systems where DMA to buffers happen to allocate these buffers properly
> aligned.
> 
> Signed-off-by: Marek Vasut <marek.vasut at gmail.com>

That second sentence is hard to parse -- I think you mean something
like, "This accommodates drivers which DMA to the buffers and have
alignment constraints."

Will a similar change be needed in Linux?

>  int nand_scan_tail(struct mtd_info *mtd)
>  {
> -	int i;
> +	int i, bufsize;
> +	uint8_t *buf;
>  	struct nand_chip *chip = mtd->priv;
>  
> -	if (!(chip->options & NAND_OWN_BUFFERS))
> -		chip->buffers = kmalloc(sizeof(*chip->buffers), GFP_KERNEL);
> -	if (!chip->buffers)
> +	if (!(chip->options & NAND_OWN_BUFFERS)) {
> +		chip->buffers = malloc(sizeof(struct nand_buffers));
> +		if (!chip->buffers)
> +			return -ENOMEM;

Why does the struct itself need to be dynamically allocated?

> +
> +		bufsize = NAND_MAX_PAGESIZE + (3 * NAND_MAX_OOBSIZE);
> +		buf = malloc(bufsize);
> +
> +		chip->buffers->buffer = (struct nand_buffers *)buf;
> +		chip->buffers->ecccalc = buf;
> +		chip->buffers->ecccode = buf + NAND_MAX_OOBSIZE;
> +		chip->buffers->databuf = buf + (2 * NAND_MAX_OOBSIZE);
> +	}
> +
> +	if (!chip->buffers->buffer)
>  		return -ENOMEM;

What does "buffer" mean now?  What would a driver that supplies its own
completely separate ecccalc/ecccode/databuf buffers put in "buffer"?

-Scott