[PATCH v2 4/6] usb: Add environment based device blocklist

[Marek Vasut]

On 3/19/24 10:17 PM, Janne Grunau wrote:

Hi,

sorry for the abysmal delay in response.

> On Mon, Mar 18, 2024 at 03:17:33PM +0100, Marek Vasut wrote:
>> On 3/18/24 8:33 AM, Janne Grunau wrote:
>>
>>>>>>> +static int usb_blocklist_parse_error(const char *blocklist, size_t pos)
>>>>>>> +{
>>>>>>> +	printf("usb_blocklist parse error at char %zu in \"%s\"\n", pos,
>>>>>>> +	       blocklist);
>>>>>>> +	return 0;
>>>>>>
>>>>>> This could be static void without return 0 at the end.
>>>>>
>>>>> the return is there to break out of the while loop on parsing errors in a single statement. This probably won't be necessary after using strsep and sscanf in the parsing function but see below.
>>>>
>>>> Ahh, now I see it. But then, shouldn't this return -ENODEV here already ?
>>>
>>> It returns 0 so that parsing errors in the blocklist do not result
>>> in blocking every USB device. That looked to me like the
>>> less bad error behavior to me.
>>
>> In unix , 0 is considered success and non-zero failure .
>>
>> How about this:
>>
>> - Return -EINVAL here (parsing failed)
> 
> If we return 0 / negated errors we do not need this function and we can
> simply report the parsing error when usb_device_is_blocked() return
> -EINVAL.
> 
>> - Instead of 'return 1' in usb_device_is_blocked() return -ENODEV
>> - In usb_select_config(), check
>>     if usb_device_is_blocked returned 0, no device blocked OK
>>     if usb_device_is_blocked returned -ENODEV, device blocked,
>>       return -ENODEV
>>     if usb_device_is_blocked returned any other error, parsing error
>>       return that error
> 
> I think the preferable option is to ignore parsing errors. If we
> would propagate the error the result would be that every USB device is
> ignored.

Good point.

>> What do you think ?
> 
> Fine by me, -EINVAL makes the parsing error reporting less awkward. Only
> open question is what should happen on parsing errors.

I agree, ignore/skip the parsing errors and report to user that 
something couldn't be parsed, that works.

> locally modified and ready to resend once we agree on the behavior on
> parsing errors

Thanks, I think we are in agreement.