linux-kernel - Re: [PATCH v3 6/6] platform/chrome: cros_ec_proto: Convert EC error codes to Linux error codes

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Date:   Wed, 29 Jul 2020 16:22:04 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Gwendal Grignou <gwendal@...omium.org>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org, linux-pwm@...r.kernel.org,
        Yu-Hsuan Hsu <yuhsuan@...omium.org>,
        Prashant Malani <pmalani@...omium.org>
Subject: Re: [PATCH v3 6/6] platform/chrome: cros_ec_proto: Convert EC error
 codes to Linux error codes

On 7/29/20 3:21 PM, Brian Norris wrote:
> Hi Guenter,
> 
> On Sun, Jul 26, 2020 at 03:01:01PM -0700, Guenter Roeck wrote:
>> v3: Use -ENOPROTOOPT for EC_RES_INVALID_VERSION
>>     Implement function to convert error codes
>> v2: No change
>>
>>  drivers/platform/chrome/cros_ec_proto.c | 52 ++++++++++++++++++++-----
>>  1 file changed, 42 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
>> index e5bbec979a2a..a081b8245682 100644
>> --- a/drivers/platform/chrome/cros_ec_proto.c
>> +++ b/drivers/platform/chrome/cros_ec_proto.c
>> @@ -15,6 +15,43 @@
>>  
>>  #define EC_COMMAND_RETRIES	50
>>  
>> +static const int cros_ec_error_map[] = {
>> +	[EC_RES_INVALID_COMMAND] = -EOPNOTSUPP,
>> +	[EC_RES_ERROR] = -EIO,
>> +	[EC_RES_INVALID_PARAM] = -EINVAL,
>> +	[EC_RES_ACCESS_DENIED] = -EACCES,
>> +	[EC_RES_INVALID_RESPONSE] = -EPROTO,
>> +	[EC_RES_INVALID_VERSION] = -ENOPROTOOPT,
>> +	[EC_RES_INVALID_CHECKSUM] = -EBADMSG,
>> +	[EC_RES_IN_PROGRESS] = -EINPROGRESS,
>> +	[EC_RES_UNAVAILABLE] = -ENODATA,
>> +	[EC_RES_TIMEOUT] = -ETIMEDOUT,
>> +	[EC_RES_OVERFLOW] = -EOVERFLOW,
>> +	[EC_RES_INVALID_HEADER] = -EBADR,
>> +	[EC_RES_REQUEST_TRUNCATED] = -EBADR,
>> +	[EC_RES_RESPONSE_TOO_BIG] = -EFBIG,
>> +	[EC_RES_BUS_ERROR] = -EFAULT,
>> +	[EC_RES_BUSY] = -EBUSY,
>> +	[EC_RES_INVALID_HEADER_VERSION] = -EBADMSG,
>> +	[EC_RES_INVALID_HEADER_CRC] = -EBADMSG,
>> +	[EC_RES_INVALID_DATA_CRC] = -EBADMSG,
>> +	[EC_RES_DUP_UNAVAILABLE] = -ENODATA,
>> +};
> 
> Sorry I didn't pay attention to this earlier, but is there any
> programmatic way to ensure that we don't have unexpected holes here? If
> we do (e.g., we add new error codes, but they aren't contiguous for
> whatever reasons), then those will get treated as "success" with your
> current patch.
> 
> I say "unexpected" hole, because EC_RES_SUCCESS (0) is an expected hole.
> 
>> +
>> +static int cros_ec_map_error(uint32_t result)
>> +{
>> +	int ret = 0;
>> +
>> +	if (result != EC_RES_SUCCESS) {
>> +		if (result < ARRAY_SIZE(cros_ec_error_map) && cros_ec_error_map[result])
>> +			ret = cros_ec_error_map[result];
> 
> ^^ Maybe we want to double check 'ret != 0'? Or maybe
> 
> 			ret = cros_ec_error_map[result];
> 			if (!ret) {

'ret' won't ever be 0 here. Above:
							&& cros_ec_error_map[result]

and below:

		else
			ret = -EPROTO;

> 				ret = -EPROTO;
> 				dev_err(..., "Unexpected EC result code %d\n", result);
> 			}
> 
> ? Could even be WARN_ON(), since this would be an actionable programming
> error, not exactly an external factor. Or maybe I'm being paranoid, and
> future programmers are perfect.
> 
I think, if anything, we might consider adding the message below (result >=
ARRAY_SIZE(cros_ec_error_map) is just as bad). Not sure myself. I am
open to adding it if people think it would be useful/desirable.

Thanks,
Guenter

> Otherwise:
> 
> Reviewed-by: Brian Norris <briannorris@...omium.org>
> 
>> +		else
>> +			ret = -EPROTO;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>>  static int prepare_packet(struct cros_ec_device *ec_dev,
>>  			  struct cros_ec_command *msg)
>>  {