Hi Peter,
Thanks for the patch! However, I suspect this will not be accepted
since the size check is an important safety measure for the general
use case.

In general layout files should be used for this sort of thing. The way
we've gone about this in the chromium.org branch is to augment the -i
syntax to allow the user to specify a region and corresponding file,
and we also added a "--fast-verify" mode to only verify regions which
were targeted. So for example you could do "flashrom -p <programmer>
-l <layout_file> -i region:filename.bin --fast-verify --ignore-fmap
-w" which will write filename.bin to the targeted region and verify
only that region.

Details here: https://www.chromium.org/chromium-os/packages/cros-flashrom#TOC-Partial-Reads-and-Writes
. LMK if this is any help.

On Mon, Nov 7, 2016 at 1:00 PM, Peter Mamonov <pmamonov@gmail.com> wrote:
> Flashrom restricts an image size to be equal to a ROM capacity. This is
> inconvenient in case of large and slow ROM chips, when only part of the ROM
> should be updated. This patch removes this restriction in a quick-and-dirty
> manner.
>
> Signed-off-by: Peter Mamonov <pmamonov@gmail.com>
> ---
>  flashrom.c | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/flashrom.c b/flashrom.c
> index d51a44c..f805e00 100644
> --- a/flashrom.c
> +++ b/flashrom.c
> @@ -1255,30 +1255,30 @@ int read_buf_from_file(unsigned char *buf, unsigned long size,
>
>         if ((image = fopen(filename, "rb")) == NULL) {
>                 msg_gerr("Error: opening file \"%s\" failed: %s\n", filename, strerror(errno));
> -               return 1;
> +               return -1;
>         }
>         if (fstat(fileno(image), &image_stat) != 0) {
>                 msg_gerr("Error: getting metadata of file \"%s\" failed: %s\n", filename, strerror(errno));
>                 fclose(image);
> -               return 1;
> +               return -1;
>         }
> -       if (image_stat.st_size != size) {
> +       if (image_stat.st_size > size) {
>                 msg_gerr("Error: Image size (%jd B) doesn't match the flash chip's size (%lu B)!\n",
>                          (intmax_t)image_stat.st_size, size);
> -               fclose(image);
> -               return 1;
> +               return -1;
>         }
> +       size = image_stat.st_size;
>         numbytes = fread(buf, 1, size, image);
>         if (fclose(image)) {
>                 msg_gerr("Error: closing file \"%s\" failed: %s\n", filename, strerror(errno));
> -               return 1;
> +               return -1;
>         }
>         if (numbytes != size) {
>                 msg_gerr("Error: Failed to read complete file. Got %ld bytes, "
>                          "wanted %ld!\n", numbytes, size);
> -               return 1;
> +               return -1;
>         }
> -       return 0;
> +       return size;
>  #endif
>  }
>
> @@ -1481,7 +1481,10 @@ static int walk_eraseregions(struct flashctx *flash, int erasefunction,
>                  * members so the loop below won't be executed for them.
>                  */
>                 len = eraser.eraseblocks[i].size;
> -               for (j = 0; j < eraser.eraseblocks[i].count; j++) {
> +               for (j = 0;
> +                    j < eraser.eraseblocks[i].count &&
> +                    start + len <= flash->chip->total_size * 1024;
> +                    j++) {
>                         /* Print this for every block except the first one. */
>                         if (i || j)
>                                 msg_cdbg(", ");
> @@ -1988,11 +1991,12 @@ int doit(struct flashctx *flash, int force, const char *filename, int read_it,
>         }
>
>         if (write_it || verify_it) {
> -               if (read_buf_from_file(newcontents, size, filename)) {
> +               size = read_buf_from_file(newcontents, size, filename);
> +               if (size < 0) {
>                         ret = 1;
>                         goto out;
>                 }
> -
> +               flash->chip->total_size = size / 1024; /* FIXME */
>  #if CONFIG_INTERNAL == 1
>                 if (programmer == PROGRAMMER_INTERNAL && cb_check_image(newcontents, size) < 0) {
>                         if (force_boardmismatch) {
> --
> 2.1.4
>
>
> _______________________________________________
> flashrom mailing list
> flashrom@flashrom.org
> https://www.flashrom.org/mailman/listinfo/flashrom

--
David Hendricks (dhendrix)
Systems Software Engineer, Google Inc.

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