[PATCH] RFC: mtd/spi-nor: add checking for the spi_nor_read

[Hou Zhiqiang]

Hi Shijie and Brian,

Do you have any comment?

> -----Original Message-----
> From: Zhiqiang Hou [mailto:B48286 at freescale.com]
> Sent: 2015年7月21日 19:57
> To: linux-mtd at lists.infradead.org; computersforpeace at gmail.com;
> dwmw2 at infradead.org
> Cc: Hu Mingkai-B21284; Hou Zhiqiang-B48286
> Subject: [PATCH] RFC: mtd/spi-nor: add checking for the spi_nor_read
> 
> From: Hou Zhiqiang <B48286 at freescale.com>
> 
> Compare the var retlen with len to ensure the read operation successful.
> 
> There are some SPI controllers that have a maximum transfer length, e.g.
> Freescale eSPI controller is able to transfer 0x10000 Bytes each time.
> If the spi_nor_read diliver a transaction length that excced the ability
> of the SPI controller, there should be multiple read operation to make
> sure this transaction completion.
> 
> Signed-off-by: Hou Zhiqiang <B48286 at freescale.com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-
> nor.c index fbc5035..ec10cd1 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -715,6 +715,8 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t
> from, size_t len,  {
>  	struct spi_nor *nor = mtd_to_spi_nor(mtd);
>  	int ret;
> +	size_t cnt = 0;
> +	u_char *cur = buf;
> 
>  	dev_dbg(nor->dev, "from 0x%08x, len %zd\n", (u32)from, len);
> 
> @@ -722,8 +724,16 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t
> from, size_t len,
>  	if (ret)
>  		return ret;
> 
> -	ret = nor->read(nor, from, len, retlen, buf);
> -
> +	*retlen = 0;
> +	while (len > 0) {
> +		ret = nor->read(nor, from, len, &cnt, cur);
> +		if (ret < 0)
> +			break;
> +		len -= cnt;
> +		cur += cnt;
> +		*retlen += cnt;
> +		from += cnt;
> +	}
>  	spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_READ);
>  	return ret;
>  }
> --
> 2.1.0.27.g96db324

Thanks,
Zhiqiang