Re: [PATCH 05/22] virtio: add support for 64 bit features.

[Rusty Russell <rusty@rustcorp.com.au>]

Ohad Ben-Cohen <ohad@wizery.com> writes:
> On Fri, Mar 22, 2013 at 4:50 PM, Sjur Brændeland <sjurbren@gmail.com> wrote:
>> I guess you would need to update the feature bits in remoteproc as well?
>> e.g. something like:
>>
>> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
>> index faf3332..148a503 100644
>> --- a/include/linux/remoteproc.h
>> +++ b/include/linux/remoteproc.h
>> @@ -296,8 +296,8 @@ struct fw_rsc_vdev_vring {
>>  struct fw_rsc_vdev {
>>         u32 id;
>>         u32 notifyid;
>> -       u32 dfeatures;
>> -       u32 gfeatures;
>> +       u64 dfeatures;
>> +       u64 gfeatures;
>>         u32 config_len;
>>         u8 status;
>>         u8 num_of_vrings;
>
> We will break existing firmware if we do that.
>
> Initially we thought it's a good idea to announce that remoteproc's
> binary interface isn't stable so we could keep changing it, but at
> this point changing the binary interface means pain for too many
> people.
>
> I'm thinking that at this stage any changes to the binary interface
> will have to bump up the binary version so we can still support older
> images, despite our "unstable" policy.

Yeah, that's why I left it alone.

Obviously, existing firmware won't set features >= 32 anyway, but you
may need to come up with a method for future extensions.

Cheers,
Rusty.
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