Re: [PATCH] platform/chrome: cros_ec_proto: Lock device when updating MKBP version

[Tzung-Bi Shih]

On Thu, Jul 25, 2024 at 05:57:13PM +0000, Patryk Duda wrote:
> The cros_ec_get_host_command_version_mask() function requires that the
> caller must have ec_dev->lock mutex before calling it. This requirement
> was not met and as a result it was possible that two commands were sent
> to the device at the same time.

To clarify:
- What would happen if multiple cros_ec_get_host_command_version_mask() calls
  at the same time?
- What are the callees?  I'm trying to understand the source of parallelism.

Also, the patch also needs an unlock at [1].

[1]: https://elixir.bootlin.com/linux/v6.10/source/drivers/platform/chrome/cros_ec_proto.c#L819

> The problem was observed while using UART backend which doesn't use any
> additional locks, unlike SPI backend which locks the controller until
> response is received.

Is it a general issue if multiple commands send to EC at a time?  If yes, it
should serialize that in the UART transportation.