Re: [PATCH 3/8] drm/i915: Use EAGAIN instead EBUSY for aux retry.

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 23 Nov 2015, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Fri, Nov 20, 2015 at 04:46:25PM -0800, Rodrigo Vivi wrote:
>> Current EBUSY meaning is immediately retry, but this is
>> about to change. DRM aux transfer is about to change and
>> make EAGAIN the immediately retry and use EBUSY to wait
>> a bit for aux channels to recover for any error or wake up.
>> 
>> This has no functional change if the EAGAIN support is in
>> place already for drm aux transfer.
>> 
>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>
> Please document the EAGAIN and EBUSY return codes for the ->transfer
> member fo drm_dp_aux in the kerneldoc properly. While at it would be great
> if you could document any other error codes that are treated specially for
> this function.

See my comment in reply to patch 1 about the difference in handling of
the ->transfer return values for native aux and i2c-over-aux.

BR,
Jani.

>
> Since this will be a bit more text please convert the kerneldoc to the new
> per-member comment layout that 4.4 supports, i.e.
>
> /**
>  * struct foo - foo structure
>  *
>  * top-level blabla
>  */
> struct foo {
> 	/**
> 	 * @bar:
> 	 *
> 	 * Long text (with paragraphs) explaining bar.
> 	 */
> };
>
> Otherwise this looks really tidy and I really like how this allows us to
> get rid of the intel_read_wake hack.
> -Daniel
>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index bec443a..ed07f0a 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -835,7 +835,7 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
>>  			last_status = status;
>>  		}
>>  
>> -		ret = -EBUSY;
>> +		ret = -EAGAIN;
>>  		goto out;
>>  	}
>>  
>> @@ -890,7 +890,7 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
>>  
>>  	if ((status & DP_AUX_CH_CTL_DONE) == 0) {
>>  		DRM_ERROR("dp_aux_ch not done status 0x%08x\n", status);
>> -		ret = -EBUSY;
>> +		ret = -EAGAIN;
>>  		goto out;
>>  	}
>>  
>> -- 
>> 2.4.3
>> 
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-- 
Jani Nikula, Intel Open Source Technology Center
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