Re: [PATCH v3] platform/chrome: Use proper protocol transfer function

[Brian Norris <briannorris@chromium.org>]

Hi,

On Tue, Sep 19, 2017 at 11:05:38PM -0700, Shawn N wrote:
> This is failing because our EC_CMD_GET_PROTOCOL_INFO host command is
> getting messed up, or the reply buffer is getting corrupted somehow.
> 
>                ec_dev->proto_version =
>                         min(EC_HOST_REQUEST_VERSION,
>                                         fls(proto_info->protocol_versions) - 1);
> 
> If proto_info->protocol_versions == 0 then ec_dev->proto_version will
> be assigned 0xffff. The logic here seems strange to me, if the EC is

Whoops...

> successfully replying to our v3 command then obviously it supports v3
> (maybe it will be useful someday if EC_HOST_REQUEST_VERSION is rev'd).
> Anyway, we need to figure out what is happening with our
> EC_HOST_REQUEST_VERSION host command.
> 
> On Tue, Sep 19, 2017 at 10:14 AM, Brian Norris <briannorris@chromium.org> wrote:
> > Hi Jon,
> >
> > On Tue, Sep 19, 2017 at 05:39:56PM +0100, Jon Hunter wrote:
> >> On 19/09/17 15:09, Shawn N wrote:
...
> > Furthermore, the only assignments to this 'proto_version' field look
> > like they're only writing one of 0, 2, 3, or
> >
> >    min(EC_HOST_REQUEST_VERSION, fls(proto_info->protocol_versions) - 1)
> >
> > . I don't see where 0xffff comes from.

...I'm an idiot. While the rvalue (the expression above) is an int (e.g,
-1), it's getting cast into a uint16_t (ec_dev->proto_version). So
that's where the 0xffff can come from.

Sorry if I misled you Shawn :(

Brian