Messages in this thread | | | From | Brian Norris <> | Date | Mon, 14 Jan 2019 18:03:54 -0800 | Subject | Re: [PATCH] mfd: cros_ec: Add support for MKBP more event flags |
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Hi Gwendal,
On Mon, Jan 14, 2019 at 3:50 PM Gwendal Grignou <gwendal@google.com> wrote: > On Fri, Dec 7, 2018 at 2:22 PM Brian Norris <briannorris@chromium.org> wrote: > > On Thu, Nov 29, 2018 at 11:55:48AM -0800, egranata@google.com wrote: > > > --- a/drivers/platform/chrome/cros_ec_proto.c > > > +++ b/drivers/platform/chrome/cros_ec_proto.c > > > @@ -420,10 +420,14 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev) > > > ret = cros_ec_get_host_command_version_mask(ec_dev, > > > EC_CMD_GET_NEXT_EVENT, > > > &ver_mask); > > > > It's not exactly new here (although you're using 'ver_mask' in new > > ways), but cros_ec_get_host_command_version_mask() doesn't look 100% > > right. It doesn't look at msg->result, and instead just assumes that if > > we got some data back (send_command() > 0), then it must have been a > > success. I don't think that's really guaranteed in general, although it > > might be for the specific case of EC_CMD_GET_CMD_VERSIONS.
> It is guaranteed: if msg->result is not EC_RES_SUCCESS, then ret can > not be greater than 0. At best it will be 0, or a negative number if > we can already qualify the error in the errno space (see > cros_ec_pkt_xfer_i2c() for instance).
Sorry, where do you guarantee that? The only enforcements I see in those xfer implementation are: (1) if result == EC_RES_IN_PROGRESS, we convert that to an errno (2) if the expected length or checksum are bad, we turn that to an errno
So technically, the EC *could* be sending a valid, checksummed response of the expected length, while still setting the ->result field to something besides EC_RES_SUCCESS or EC_RES_IN_PROGRESS. And we would treat that as a valid 'ver_mask'.
Albeit, that seems unlikely, given understanding of how the EC is supposed to behave, but our code is not properly defensive AIUI. This is basically why cros_ec_cmd_xfer_status() exists -- so that sub-drivers don't get lazy and use cros_ec_cmd_xfer() without handling the ->result field properly.
Brian
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