Re: [PATCH v3 4/4] mtd: Fallback to ->_read/write_oob() when ->_read/write() is missing

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Fri, 15 Dec 2017 13:39:54 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> Some MTD sublayers/drivers are implementing ->_read/write_oob() and
> provide dummy wrappers for their ->_read/write() implementations.
> Let the core handle this case instead of duplicating the logic.

Also dropped this patch since it depends on patch 3. I'll send a new
version soon.

> 
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
> Acked-by: Brian Norris <computersforpeace@gmail.com>
> ---
> Changes in v3:
> - none
> 
> Changes in v2:
> - none
> ---
>  drivers/mtd/devices/docg3.c        | 65 --------------------------------------
>  drivers/mtd/mtdcore.c              | 31 ++++++++++++++++--
>  drivers/mtd/nand/nand_base.c       | 56 --------------------------------
>  drivers/mtd/onenand/onenand_base.c | 63 ------------------------------------
>  4 files changed, 29 insertions(+), 186 deletions(-)
> 
> diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
> index 0806f72102c0..5fb5e93d1547 100644
> --- a/drivers/mtd/devices/docg3.c
> +++ b/drivers/mtd/devices/docg3.c
> @@ -990,36 +990,6 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
>  	goto out;
>  }
>  
> -/**
> - * doc_read - Read bytes from flash
> - * @mtd: the device
> - * @from: the offset from first block and first page, in bytes, aligned on page
> - *        size
> - * @len: the number of bytes to read (must be a multiple of 4)
> - * @retlen: the number of bytes actually read
> - * @buf: the filled in buffer
> - *
> - * Reads flash memory pages. This function does not read the OOB chunk, but only
> - * the page data.
> - *
> - * Returns 0 if read successful, of -EIO, -EINVAL if an error occurred
> - */
> -static int doc_read(struct mtd_info *mtd, loff_t from, size_t len,
> -	     size_t *retlen, u_char *buf)
> -{
> -	struct mtd_oob_ops ops;
> -	size_t ret;
> -
> -	memset(&ops, 0, sizeof(ops));
> -	ops.datbuf = buf;
> -	ops.len = len;
> -	ops.mode = MTD_OPS_AUTO_OOB;
> -
> -	ret = doc_read_oob(mtd, from, &ops);
> -	*retlen = ops.retlen;
> -	return ret;
> -}
> -
>  static int doc_reload_bbt(struct docg3 *docg3)
>  {
>  	int block = DOC_LAYOUT_BLOCK_BBT;
> @@ -1513,39 +1483,6 @@ static int doc_write_oob(struct mtd_info *mtd, loff_t ofs,
>  	return ret;
>  }
>  
> -/**
> - * doc_write - Write a buffer to the chip
> - * @mtd: the device
> - * @to: the offset from first block and first page, in bytes, aligned on page
> - *      size
> - * @len: the number of bytes to write (must be a full page size, ie. 512)
> - * @retlen: the number of bytes actually written (0 or 512)
> - * @buf: the buffer to get bytes from
> - *
> - * Writes data to the chip.
> - *
> - * Returns 0 if write successful, -EIO if write error
> - */
> -static int doc_write(struct mtd_info *mtd, loff_t to, size_t len,
> -		     size_t *retlen, const u_char *buf)
> -{
> -	struct docg3 *docg3 = mtd->priv;
> -	int ret;
> -	struct mtd_oob_ops ops;
> -
> -	doc_dbg("doc_write(to=%lld, len=%zu)\n", to, len);
> -	ops.datbuf = (char *)buf;
> -	ops.len = len;
> -	ops.mode = MTD_OPS_PLACE_OOB;
> -	ops.oobbuf = NULL;
> -	ops.ooblen = 0;
> -	ops.ooboffs = 0;
> -
> -	ret = doc_write_oob(mtd, to, &ops);
> -	*retlen = ops.retlen;
> -	return ret;
> -}
> -
>  static struct docg3 *sysfs_dev2docg3(struct device *dev,
>  				     struct device_attribute *attr)
>  {
> @@ -1866,8 +1803,6 @@ static int __init doc_set_driver_info(int chip_id, struct mtd_info *mtd)
>  	mtd->writebufsize = mtd->writesize = DOC_LAYOUT_PAGE_SIZE;
>  	mtd->oobsize = DOC_LAYOUT_OOB_SIZE;
>  	mtd->_erase = doc_erase;
> -	mtd->_read = doc_read;
> -	mtd->_write = doc_write;
>  	mtd->_read_oob = doc_read_oob;
>  	mtd->_write_oob = doc_write_oob;
>  	mtd->_block_isbad = doc_block_isbad;
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 642c35dde686..d7ab091b36b2 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -1058,7 +1058,20 @@ int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
>  	 * representing the maximum number of bitflips that were corrected on
>  	 * any one ecc region (if applicable; zero otherwise).
>  	 */
> -	ret_code = mtd->_read(mtd, from, len, retlen, buf);
> +	if (mtd->_read) {
> +		ret_code = mtd->_read(mtd, from, len, retlen, buf);
> +	} else if (mtd->_read_oob) {
> +		struct mtd_oob_ops ops = {
> +			.len = len,
> +			.datbuf = buf,
> +		};
> +
> +		ret_code = mtd->_read_oob(mtd, from, &ops);
> +		*retlen = ops.retlen;
> +	} else {
> +		return -ENOTSUPP;
> +	}
> +
>  	if (unlikely(ret_code < 0))
>  		return ret_code;
>  	if (mtd->ecc_strength == 0)
> @@ -1073,11 +1086,25 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  	*retlen = 0;
>  	if (to < 0 || to >= mtd->size || len > mtd->size - to)
>  		return -EINVAL;
> -	if (!mtd->_write || !(mtd->flags & MTD_WRITEABLE))
> +	if ((!mtd->_write && !mtd->_write_oob) ||
> +	    !(mtd->flags & MTD_WRITEABLE))
>  		return -EROFS;
>  	if (!len)
>  		return 0;
>  	ledtrig_mtd_activity();
> +
> +	if (!mtd->_write) {
> +		struct mtd_oob_ops ops = {
> +			.len = len,
> +			.datbuf = (u8 *)buf,
> +		};
> +		int ret;
> +
> +		ret = mtd->_write_oob(mtd, to, &ops);
> +		*retlen = ops.retlen;
> +		return ret;
> +	}
> +
>  	return mtd->_write(mtd, to, len, retlen, buf);
>  }
>  EXPORT_SYMBOL_GPL(mtd_write);
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 6135d007a068..889ceadbf607 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2027,33 +2027,6 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
>  }
>  
>  /**
> - * nand_read - [MTD Interface] MTD compatibility function for nand_do_read_ecc
> - * @mtd: MTD device structure
> - * @from: offset to read from
> - * @len: number of bytes to read
> - * @retlen: pointer to variable to store the number of read bytes
> - * @buf: the databuffer to put data
> - *
> - * Get hold of the chip and call nand_do_read.
> - */
> -static int nand_read(struct mtd_info *mtd, loff_t from, size_t len,
> -		     size_t *retlen, uint8_t *buf)
> -{
> -	struct mtd_oob_ops ops;
> -	int ret;
> -
> -	nand_get_device(mtd, FL_READING);
> -	memset(&ops, 0, sizeof(ops));
> -	ops.len = len;
> -	ops.datbuf = buf;
> -	ops.mode = MTD_OPS_PLACE_OOB;
> -	ret = nand_do_read_ops(mtd, from, &ops);
> -	*retlen = ops.retlen;
> -	nand_release_device(mtd);
> -	return ret;
> -}
> -
> -/**
>   * nand_read_oob_std - [REPLACEABLE] the most common OOB data read function
>   * @mtd: mtd info structure
>   * @chip: nand chip info structure
> @@ -2822,33 +2795,6 @@ static int panic_nand_write(struct mtd_info *mtd, loff_t to, size_t len,
>  }
>  
>  /**
> - * nand_write - [MTD Interface] NAND write with ECC
> - * @mtd: MTD device structure
> - * @to: offset to write to
> - * @len: number of bytes to write
> - * @retlen: pointer to variable to store the number of written bytes
> - * @buf: the data to write
> - *
> - * NAND write with ECC.
> - */
> -static int nand_write(struct mtd_info *mtd, loff_t to, size_t len,
> -			  size_t *retlen, const uint8_t *buf)
> -{
> -	struct mtd_oob_ops ops;
> -	int ret;
> -
> -	nand_get_device(mtd, FL_WRITING);
> -	memset(&ops, 0, sizeof(ops));
> -	ops.len = len;
> -	ops.datbuf = (uint8_t *)buf;
> -	ops.mode = MTD_OPS_PLACE_OOB;
> -	ret = nand_do_write_ops(mtd, to, &ops);
> -	*retlen = ops.retlen;
> -	nand_release_device(mtd);
> -	return ret;
> -}
> -
> -/**
>   * nand_do_write_oob - [MTD Interface] NAND write out-of-band
>   * @mtd: MTD device structure
>   * @to: offset to write to
> @@ -4917,8 +4863,6 @@ int nand_scan_tail(struct mtd_info *mtd)
>  	mtd->_erase = nand_erase;
>  	mtd->_point = NULL;
>  	mtd->_unpoint = NULL;
> -	mtd->_read = nand_read;
> -	mtd->_write = nand_write;
>  	mtd->_panic_write = panic_nand_write;
>  	mtd->_read_oob = nand_read_oob;
>  	mtd->_write_oob = nand_write_oob;
> diff --git a/drivers/mtd/onenand/onenand_base.c b/drivers/mtd/onenand/onenand_base.c
> index 1a6d0e367b89..050ba8a87543 100644
> --- a/drivers/mtd/onenand/onenand_base.c
> +++ b/drivers/mtd/onenand/onenand_base.c
> @@ -1448,38 +1448,6 @@ static int onenand_read_oob_nolock(struct mtd_info *mtd, loff_t from,
>  }
>  
>  /**
> - * onenand_read - [MTD Interface] Read data from flash
> - * @param mtd		MTD device structure
> - * @param from		offset to read from
> - * @param len		number of bytes to read
> - * @param retlen	pointer to variable to store the number of read bytes
> - * @param buf		the databuffer to put data
> - *
> - * Read with ecc
> -*/
> -static int onenand_read(struct mtd_info *mtd, loff_t from, size_t len,
> -	size_t *retlen, u_char *buf)
> -{
> -	struct onenand_chip *this = mtd->priv;
> -	struct mtd_oob_ops ops = {
> -		.len	= len,
> -		.ooblen	= 0,
> -		.datbuf	= buf,
> -		.oobbuf	= NULL,
> -	};
> -	int ret;
> -
> -	onenand_get_device(mtd, FL_READING);
> -	ret = ONENAND_IS_4KB_PAGE(this) ?
> -		onenand_mlc_read_ops_nolock(mtd, from, &ops) :
> -		onenand_read_ops_nolock(mtd, from, &ops);
> -	onenand_release_device(mtd);
> -
> -	*retlen = ops.retlen;
> -	return ret;
> -}
> -
> -/**
>   * onenand_read_oob - [MTD Interface] Read main and/or out-of-band
>   * @param mtd:		MTD device structure
>   * @param from:		offset to read from
> @@ -2129,35 +2097,6 @@ static int onenand_write_oob_nolock(struct mtd_info *mtd, loff_t to,
>  }
>  
>  /**
> - * onenand_write - [MTD Interface] write buffer to FLASH
> - * @param mtd		MTD device structure
> - * @param to		offset to write to
> - * @param len		number of bytes to write
> - * @param retlen	pointer to variable to store the number of written bytes
> - * @param buf		the data to write
> - *
> - * Write with ECC
> - */
> -static int onenand_write(struct mtd_info *mtd, loff_t to, size_t len,
> -	size_t *retlen, const u_char *buf)
> -{
> -	struct mtd_oob_ops ops = {
> -		.len	= len,
> -		.ooblen	= 0,
> -		.datbuf	= (u_char *) buf,
> -		.oobbuf	= NULL,
> -	};
> -	int ret;
> -
> -	onenand_get_device(mtd, FL_WRITING);
> -	ret = onenand_write_ops_nolock(mtd, to, &ops);
> -	onenand_release_device(mtd);
> -
> -	*retlen = ops.retlen;
> -	return ret;
> -}
> -
> -/**
>   * onenand_write_oob - [MTD Interface] NAND write data and/or out-of-band
>   * @param mtd:		MTD device structure
>   * @param to:		offset to write
> @@ -4038,8 +3977,6 @@ int onenand_scan(struct mtd_info *mtd, int maxchips)
>  	mtd->_erase = onenand_erase;
>  	mtd->_point = NULL;
>  	mtd->_unpoint = NULL;
> -	mtd->_read = onenand_read;
> -	mtd->_write = onenand_write;
>  	mtd->_read_oob = onenand_read_oob;
>  	mtd->_write_oob = onenand_write_oob;
>  	mtd->_panic_write = onenand_panic_write;