linux-kernel - Re: [PATCH 6/7] platform/chrome: cros_ec

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Date:   Wed, 28 Oct 2020 13:11:35 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH 6/7] platform/chrome: cros_ec_typec: Parse partner PD ID
 VDOs

Hi Heikki,

Thanks a lot for reviewing the patch!

On Wed, Oct 28, 2020 at 03:16:33PM +0200, Heikki Krogerus wrote:
> > +
> > +	/* Copy the remaining identity VDOs till a maximum of 6. */
> > +	for (i = 3; i < sop_disc->identity_count && i < VDO_MAX_OBJECTS; i++)
> > +		port->p_identity.vdo[i - 3] = sop_disc->discovery_vdo[i];
> 
> Why do you need to put the product type VDOs in reverse order?

The Chrome EC returns all the Identity VDOs as an array of 6 VDOs (the
discovery_vdo[] array). The first three entries are assigned to the
pd_identity.{id_header,cert_stat,product} members.

This for loop assigns the next three discovery_vdo entries (i.e indices
3-5) to pd_identity.vdo[0-2] respectively.

The "i-3" is because discovery_vdo[3] corresponds to pd_identity.vdo[0]
and so on.

Does that help to clarify the for loop?

Best regards,

Prashant