[PATCH 1/1] cros_ec: Handling EC_CMD_GET_NEXT_EVENT

[Heinrich Schuchardt]

On 11/9/20 10:13 PM, Alper Nebi Yasak wrote:
> On 09/11/2020 23:34, Heinrich Schuchardt wrote:
>> With commit 690079767803 ("cros_ec: Support keyboard scanning with
>> EC_CMD_GET_NEXT_EVENT") check_for_keys() tries to read keyboard
>> strokes using EC_CMD_GET_NEXT_EVENT. But the sandbox driver does
>> not understand this command. We need to reply with
>> -EC_RES_INVALID_COMMAND to force check_for_keys() to fall back to
>> use EC_CMD_MKBP_STATE. Currently the driver prints
>>
>>     ** Unknown EC command 0x67
>>
>> in this case. With the patch the message is suppressed.
>>
>> In a future patch we should upgrade the sandbox driver to provide
>> EC_CMD_GET_NEXT_EVENT support.
>>
>> Fixes: 690079767803 ("cros_ec: Support keyboard scanning with EC_CMD_GET_NEXT_EVENT")
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> ---
>> process_cmd() should always return an appropriate negative enum ec_status
>> in case of an error and not simply -1. But fixing the return values is
>> beyond the scope of this patch.
>
> (Looks to me like -1 is already == -EC_RES_INVALID_COMMAND from
> include/ec_commands.h definitions, but I'd agree the latter form should
> be preferred.)

If you look at the complete function, you will find other "return -1;"
statements where return codes other than -EC_RES_INVALID_COMMAND make
more sense. E.g. after

    printf("** Unknown flash region %d\n", req->region);

it would be reasonable to return EC_RES_INVALID_PARAM.

Best regards

Heinrich

>
>> ---
>>  drivers/misc/cros_ec_sandbox.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/misc/cros_ec_sandbox.c b/drivers/misc/cros_ec_sandbox.c
>> index a191f061b8..ff7f782742 100644
>> --- a/drivers/misc/cros_ec_sandbox.c
>> +++ b/drivers/misc/cros_ec_sandbox.c
>> @@ -460,6 +460,16 @@ static int process_cmd(struct ec_state *ec,
>>  	case EC_CMD_ENTERING_MODE:
>>  		len = 0;
>>  		break;
>> +	case EC_CMD_GET_NEXT_EVENT:
>> +		/*
>> +		 * TODO:
>> +		 * This driver emulates an old keyboard device supporting
>> +		 * EC_CMD_MKBP_STATE. Current Chrome OS keyboards use
>> +		 * EC_CMD_GET_NEXT_EVENT. Cf.
>> +		 * "mkbp: Add support for buttons and switches"
>> +		 * https://chromium.googlesource.com/chromiumos/platform/ec/+/87a071941b89e3f7fd3eb329b682e60b3fbd6c73
>> +		 */
>> +		return -EC_RES_INVALID_COMMAND;
>
> I'll try implementing the TODO, sorry for the fallout.
>
>>  	default:
>>  		printf("   ** Unknown EC command %#02x\n", req_hdr->command);
>>  		return -1;
>> --
>> 2.28.0
>>