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

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@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