[U-Boot] [PATCH] Document config_distro_bootcmd environment variables for interactive booting.

[Stephen Warren <swarren@wwwdotorg.org>]

On 03/19/2015 02:53 PM, Karsten Merker wrote:
> On Thu, Mar 19, 2015 at 01:53:14PM -0600, Stephen Warren wrote:
>
>>> +Interactively booting from a specific device at the u-boot prompt
>>> +=================================================================
>>> +
>>> +For interactively booting from a user-selected device at the u-boot command
>>> +prompt, the environment provides predefined bootcmd_<target> variables for
>>> +every target defined in boot_targets, which can be run be the user.
>>> +
>>> +Examples:
>>> +
>>> + - run bootcmd_usb0
>>> +   boots from the first USB mass storage device
>>> +
>>> + - run bootcmd_mmc1
>>> +   boots from the second MMC device
>>
>> Should we enumerate all the possible device types, e.g. include
>> bootcmd_sata0, bootcmd_ide0, ...?
>
> Hm, I suppose that depends on whether there is such a thing as
> definitve list of all possible device types on all platforms and
> how many elements are in this list.  Are functionally equivalent
> devices named the same on all platforms, i.e. is a PATA
> interface always ide0, or could it be ide0 on one platform and
> pata0 on another?

The list is limited to the macros that are set up in 
config_distro_bootcmd.h. At least for the device types supported there, 
and the set of platforms which use that header so far, a particular 
device type is always named the same on all platforms.

I'd expect a patch that added a new device type to the header to update 
the list in the documentation.

>> In the text, perhaps rephrase bootcmd_<target> as
>> bootcmd_<devtype><devnum>, and note that <devnum> is not optional in the
>> command name?
>
> I had thought about explictly using devtype and devnum, but there
> are device types such as pxe which do not have a devnum, so I
> chose to use the generic <target> designation instead. I can
> change that, but it might cause confusion so that a user would
> try to use something like "run bootcmd_pxe0" which would not
> work. I would therefore prefer the generic <target> designation.

Ah yes. Perhaps continue to use <target> and then explain that when 
<target> is a storage device that can have multiple instances, the 
format of <target> must be <devtype><devnum>, but in other cases (pxe, 
dhcp), it is just a standalone name?