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Date: Tue, 11 Jun 2024 10:14:41 +0000
From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= <linux@weissschuh.net>
Cc: Benson Leung <bleung@chromium.org>, Guenter Roeck <groeck@chromium.org>,
	Sebastian Reichel <sre@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Len Brown <lenb@kernel.org>, Robert Moore <robert.moore@intel.com>,
	chrome-platform@lists.linux.dev, linux-kernel@vger.kernel.org,
	linux-pm@vger.kernel.org,
	Mario Limonciello <mario.limonciello@amd.com>,
	Dustin Howett <dustin@howett.net>,
	Stephen Horvath <s.horvath@outlook.com.au>,
	Rajas Paranjpe <paranjperajas@gmail.com>,
	linux-acpi@vger.kernel.org, acpica-devel@lists.linux.dev,
	Matt Hartley <matt.hartley@gmail.com>
Subject: Re: [PATCH v3 3/5] platform/chrome: cros_ec_proto: Introduce
 cros_ec_cmd_versions()
Message-ID: <ZmgjkVXZEe6BkZzq@google.com>
References: <20240610-cros_ec-charge-control-v3-0-135e37252094@weissschuh.net>
 <20240610-cros_ec-charge-control-v3-3-135e37252094@weissschuh.net>
 <ZmfvhvcjTbjOSp4f@google.com>
 <f2a361aa-a256-41a5-8100-703e40df975d@t-8ch.de>
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In-Reply-To: <f2a361aa-a256-41a5-8100-703e40df975d@t-8ch.de>

On Tue, Jun 11, 2024 at 09:23:24AM +0200, Thomas Weißschuh wrote:
> On 2024-06-11 06:32:38+0000, Tzung-Bi Shih wrote:
> > On Mon, Jun 10, 2024 at 05:51:08PM +0200, Thomas Weißschuh wrote:
> > > If the command is not supported at all the EC returns
> > > -EINVAL/EC_RES_INVALID_PARAMS.
> > > 
> > > This error is translated into an empty version mask as that is easier to
> > > handle for callers and they don't need to know about the error details.
> > 
> > I'm not sure whether the behavior is what we want or not as existing
> > EC_CMD_GET_CMD_VERSIONS usages don't have it.
> 
> At least the caller of cros_ec_get_host_command_version_mask() expects
> it:
> 
> ret = cros_ec_get_host_command_version_mask(..., &ver_mask);
> if (ret < 0 || ver_mask == 0)
> ...
> 
> ver_mask == 0 will never happen as in that case -EINVAL would have been
> returned.
> 
> Others, like cros_ec_cec_get_write_cmd_version(), expect the current
> semantic of ver_mask != 0 but log spurious errors in case of -EINVAL.
> cros_pchg_cmd_ver_check(), works with both semantics, but currently also
> logs a spurious error message.
> 
> To me the new semantic looks more obvious and much easier to handle.
> For each command version a bit is set. no command versions -> no bits.

Ack.