[U-Boot] [PATCH 5/6] Support environment anywhere within erase area

[Wolfgang Denk]

Dear Guennadi Liakhovetski,

In message <Pine.LNX.4.64.0808271747470.6718 at axis700.grange> you wrote:
> This will become more important with NAND support, in which case the minimum
> erase region is a block, which consists of several pages and can be 256KiB
> large.

Please explain.

What does "anywhere" mean? At offset 0, 1, 5, 17 or 42? Or what?  And
what exactly is the "erase area" ?

And where's the difference between NAND and NOR flash? For  NOR,  the
minimum "erase region" is a "block", either, which also can be 256KiB
large.

> +	/*
> +	 * Support environment anywhere within erase sectors: read out the
> +	 * complete area to be erased, replace the environment image, write
> +	 * the whole block back again.
> +	 */
> +	if (DEVESIZE (dev_target) > CFG_ENV_SIZE) {
> +		data = malloc (DEVESIZE (dev_target));
> +		if (!data) {
> +			fprintf (stderr,
> +				 "Cannot malloc %lu bytes: %s\n",
> +				 DEVESIZE (dev_target),
> +				 strerror (errno));
> +			return -1;
> +		}
> +
> +		rc = ioctl (fd_target, MEMGETINFO, &mtdinfo_target);
> +		if (rc < 0) {
> +			perror ("Cannot get MTD information");
> +			return -1;
> +		}
> +
> +		/* Erase sector size is always a power of 2 */
> +		erase_offset = DEVOFFSET (dev_target) &
> +			~(mtdinfo_target.erasesize - 1);
> +
> +		rc = flash_read_buf (dev_target, fd_target, data,
> +				     DEVESIZE (dev_target), erase_offset);
> +		if (rc < 0)
> +			return rc;
> +
> +		/* Overwrite the old environment */
> +		memcpy(DEVOFFSET (dev_target) - erase_offset + data,
> +		       environment.image, CFG_ENV_SIZE);
> +	} else {
> +		data = (char *)environment.image;
> +		erase_offset = DEVOFFSET (dev_target);
> +	}

You are talking about "several pages" above. Where is this refelected
in the code?


Frankly, I don't understand what you are trying to do. Please explain
your implementation.

Best regards,

Wolfgang Denk

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