Re: [U-Boot] [PATCH] fw_setenv: avoid writing environment when nothing has changed

24 Sep 2018

On Wed, Sep 5, 2018 at 8:23 PM Rasmus Villemoes
rasmus.villemoes@prevas.dk wrote:
...
In the case where one deletes an already-non-existing variable, or sets
a variable to the value it already has, there is no point in writing the
environment back, thus reducing wear on the underlying storage
device.
Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk
If you were running with a redundant env, and you were trying to sync
both copies, wouldn't you want a non-changing write to happen?
...

tools/env/fw_env.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index a5d75958e1..87aaa15198 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -110,6 +110,7 @@ struct environment {
        unsigned char *flags;
        char *data;
        enum flag_scheme flag_scheme;

  int dirty;



};
static struct environment environment = {
@@ -508,6 +509,9 @@ int fw_env_flush(struct env_opts *opts)
        if (!opts)
                opts = &default_opts;

  if (!environment.dirty)


          return 0;


  /*
   * Update CRC
   */



@@ -553,7 +557,8 @@ int fw_env_write(char *name, char *value)
    deleting = (oldval && !(value && strlen(value)));
    creating = (!oldval && (value && strlen(value)));


  overwriting = (oldval && (value && strlen(value)));




  overwriting = (oldval && (value && strlen(value) &&


                            strcmp(oldval, value)));

  /* check for permission */
  if (deleting) {



@@ -593,6 +598,7 @@ int fw_env_write(char *name, char *value)
                /* Nothing to do */
                return 0;

  environment.dirty = 1;
  if (deleting || overwriting) {
          if (*++nxt == '\0') {
                  *env = '\0';



@@ -1441,6 +1447,7 @@ int fw_env_open(struct env_opts *opts)
                                "Warning: Bad CRC, using default environment\n");
                        memcpy(environment.data, default_environment,
                               sizeof(default_environment));

                  environment.dirty = 1;
          }
  } else {
          flag0 = *environment.flags;



@@ -1503,6 +1510,7 @@ int fw_env_open(struct env_opts *opts)
                                "Warning: Bad CRC, using default environment\n");
                        memcpy(environment.data, default_environment,
                               sizeof(default_environment));

                  environment.dirty = 1;
                  dev_current = 0;
          } else {
                  switch (environment.flag_scheme) {



--
2.16.4

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Alex Kiernan

    