[U-Boot] [RFC PATCH 2/2] fs: add partition switch libary, implement ls and fsload commands

[Stephen Warren <swarren@wwwdotorg.org>]

On 10/11/2012 10:47 AM, Tom Rini wrote:
> On 10/10/12 17:05, Stephen Warren wrote:
>> From: Stephen Warren <swarren@nvidia.com>
> 
>> Implement "ls" and "fsload" commands that act like 
>> {fat,ext2}{ls,load}, and transparently handle either file-system.
>>  This scheme could easily be extended to other filesystem types;
>> I only didn't do it for zfs because I don't have any filesystems
>> of that type.
> 
>> Signed-off-by: Stephen Warren <swarren@nvidia.com> --- There are
>> a couple FIXMEs in here:
> 
>> 1) In fs/fs.c, code is ifdef on CONFIG_CMD_FAT or
>> CONFIG_CMD_EXT2. This means that the new commands and code can
>> only be enabled if the "legacy" {fat,ext2}{ls,load} are enabled.
>> What we really want is CONFIG_FS_FAT and CONFIG_FS_EXT2 to enable
>> the filesystem code, and then CONFIG_CMD_FAT, CONFIG_CMD_EXT2,
>> CONFIG_CMD_FS to only affect the command implementations.
>> However, that would require making every include/config/*.h that
>> sets the current defines also set more. I suppose that's a fairly
>> mechanical change though, so easy enough to implement. Does that
>> seem like a reasonable approach to people?
> 
> How about a new CONFIG_CMD_GENERIC_FS for the new ls/fsload (and
> any later commands like write that get added) and once most
> filesystems are converted we can think about a transition plan?

Certainly.

The issue is that the filesystem code itself is conditionally included
based on CONFIG_CMD_FAT and CONFIG_CMD_EXT4. This would require that
in order to use the new generic commands, you also had to support the
old non-generic commands in order to get a linkable result. Perhaps
that's fine for now, but by separating the existing CONFIG_CMD_FAT
into two (CONFIG_CMD_FAT, CONFIG_FS_FAT), we could avoid that
requirement. As Benoit mentioned, perhaps we could arrange that
CONFIG_CMD_FAT selects CONFIG_FS_FAT somehow, although I haven't
looked at U-Boot's configuration system to see if that's possible yet.