[U-Boot] [PATCH 1/1]: filesystems : add "file exists" cmd

[Sergey Kubushyn]

On Sat, 8 Oct 2016, Tom Rini wrote:

> On Wed, Oct 05, 2016 at 12:38:01PM -0700, Sergey Kubushyn wrote:
>
>> This adds "file exists" commands to generic FS as well as to FAT, EXT4,
>> and UBIFS. Also adds "file size" command to UBIFS.
>>
>> The return value for "file exists" commands is REVERSED i.e. they
>> return 1 if file exists and 0 otherwise. This is a deliberate decision
>> because those commands are supposed to be used almost exclusively in
>> scripts and TRUE value is _not_ zero while FALSE is zero.
>>
>> As of now the only way to check for a file existence is to attempt a
>> read on that file (aka load.) That works but it makes an unnecessary
>> read, overwrites memory at destination address if file not a zero
>> length one, and outputs unnecessary messages to the console in any
>> case.
>>
>> Checking file existence in scripts is a valuable feature that allows
>> the higher level software (e.g. Linux) to interact with U-Boot by
>> creating some semaphore files and rebooting. We do use it quite
>> extensively for system setup at manufacturing time and for other
>> purposes (e.g. our Android "recovery" is implemented this way.)
>>
>> Signed-off-by: Sergey Kubushyn <ksi at koi8.net>
>
> Can you please do this in at least two patches?  file size to ubi should
> be its own patch.  Also:

Sure, will do later today.

>> +int do_ext4_file_exists(cmd_tbl_t *cmdtp, int flag, int argc,
>> +						char *const argv[])
>> +{
>> +	int ret;
>> +
>> +	ret = do_file_exists(cmdtp, flag, argc, argv, FS_TYPE_EXT);
>> + +	if (ret == 0) return 1;
>> +	if (ret == 1) return 0;
>> +	return ret;
>> +}
>
> I can only assume this hasn't been compile tested in a while, and you
> should simplify the code into a single if/else and a comment on what we
> want/mean.  Thanks!

The problem is do_file_exists() can return not just 0 if file exists or
1 if it doesn't but also a negative value for "I don't know" i.e. when
e.g. FS mount failed.

I don't know if those return codes are somehow processed further up (too
much time to dig everything to the bare metal) so I decided to return
that value as-is if it happened. Sure it could be done like e.g.

 	return (ret == 0);

even without any if-elses and it is probably the proper way to do it but
I fell victim of perfectionism :))

Will re-do it with the above construction and split in 2 parts. Will also
send it with git send-email so it won't end up garbled.

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