Re: one last firmware(9) issue

On Thursday 15 February 2007 18:43, Luigi Rizzo wrote:
> I have committed the cleanup to firmware(9) discussed earlier
> on this list, see the commit log below. There is a remaining issue
> on which i would like some advice. From the commit log:
>
>     Note also that there is a subtle issue with the implementation of
>     firmware_register(): currently, as in the previous version, we just
>     store a reference to the 'imagename' argument, but we should rather
>     copy it because there is no guarantee that this is a static string.
>
> Now, what do you think is the best way to handle this ? The existing
> code tries not to allocate memory on a firmware_register(), not
> sure if it is on purpose (e.g. to avoid sleeping) or for other
> reasons.  To preserve this, we should use static buffers for the
> image names, and pick a reasonable size for them (128 ? 256 ? 1025 ?).
>
> If on the other hand, we can afford a malloc in firmware_register(),
> i'd move the whole registry to a linked list, to avoid the hard limit
> of 30 slots in the firmware table.
>
> suggestions ?

I say, let the caller deal with it.  After all the caller must ensure that 
the firmware itself stays in memory until they call firmware_unregister, 
why should we jump through all the hoops for the name?

The linked list is another thing.  As I recall, the static array is only 
there due to our lazyness.  It's a lot easier to use a static array and I 
don't forsee us using more than 30 firmware images at a time.  OTOH, it 
would of course be nice to have a more flexible system.  I'm not 100% 
certain what the locking constrains for firmware_register() are.  Usually 
it is called from the mod_event of a firmware module, which in turn is 
called from the linker subsystem.  There might be some locks involved 
that would prevent you from sleeping, but that's just a wild guess.

Thanks for taking care of this, by the way.  Much appreciated.

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