Re: [PATCH 1/3] mfd: cros_ec: Add Chrome OS EC userspace device interface

From: Javier Martinez Canillas
Date: Thu Nov 20 2014 - 05:03:22 EST

Hello Olof,

On 11/19/2014 09:45 PM, Olof Johansson wrote:
>> Is true that this is a new API for mainline but there is a lot of ChromeOS
>> installations that depends on this API which means that just replacing the
>> kernel with a mainline one there, will break existing user-space programs.
> I think we can deal with that, at least if we pick new ioctl numbers
> so we can tell from the userspace tool which interface is in use
> during transition.
>> But I understand that since those binaries were using a non-ustream kernel
>> it is expected that the kernel API could be changed.
>> I think it would be great to keep existing binaries working but if changing
>> the API is required, then I can certainly do that when doing a re-spin.
> I think there's some value in that, but i'm also somewhat embarrassed
> to have missed this aspect when doing internal review, and do agree
> with Alan. :) And we have only a few tools that use this interface so
> we should be able to cope with it.

Thanks a lot for your feedback. I'll follow Alan suggestion then and make
the structs to be 64-bit safe and properly padded. Also, I'll follow your
suggestion and use a different magic number for the IOCTLs so user-space
programs can be backward compatible if needed.

> -Olof

Best regards,
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