RE: [PATCH] drm/dp: Fix Write_Status_Update_Request AUX request format

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

On Thu, 08 May 2025, "Lin, Wayne" <Wayne.Lin@amd.com> wrote:
> [Public]
>
>> -----Original Message-----
>> From: Jani Nikula <jani.nikula@intel.com>
>> Sent: Thursday, May 8, 2025 4:19 PM
>> To: Lin, Wayne <Wayne.Lin@amd.com>; dri-devel@lists.freedesktop.org
>> Cc: ville.syrjala@linux.intel.com; Limonciello, Mario <Mario.Limonciello@amd.com>;
>> Wentland, Harry <Harry.Wentland@amd.com>; Lin, Wayne
>> <Wayne.Lin@amd.com>; stable@vger.kernel.org
>> Subject: Re: [PATCH] drm/dp: Fix Write_Status_Update_Request AUX request
>> format
>>
>> On Sun, 27 Apr 2025, Wayne Lin <Wayne.Lin@amd.com> wrote:
>> > +                   /*
>> > +                    * When I2C write firstly get defer and get ack after
>> > +                    * retries by wirte_status_update, we have to return
>> > +                    * all data bytes get transferred instead of 0.
>> > +                    */
>>
>> My brain gives me syntax and parse error here. ;)
>
> Appreciate for the feedback, Jani.
> Could you elaborate more on your concerns please?
>
> Since Write_Status_Update_Request is address only request. Data length
> is 0. When I2C write request completes, reply for
> Write_Status_Update_Request from DPRx will be ACK only (i.e. data
> length is 0).
>
> Is your concern about returning 0 from aux->transfer?
> My thoughts is drm_dp_i2c_do_msg() is designed to handle I2C-Over-Aux
> reply data, and aux->transfer() is handling hw specific manipulation and
> return transferred bytes. For Write_Status_Update_Request request itself,
> nothing new to be transferred. I think drm_dp_i2c_do_msg() should be
> responsible for determining the correct transferred data bytes under this
> case. Or do you expect aux->transfer to memorize the data length of
> write request?

My concern is that I don't understand what the comment is trying to say.

"when i2c write firstly get defer" - what does it mean?

"wirte_status_update" - typo

"we have to" - why?

"return all data bytes get transferred" - what does it mean?

>
> Thanks!
>>
>> BR,
>> Jani.
>>
>> --
>> Jani Nikula, Intel
> --
> Wayne Lin

-- 
Jani Nikula, Intel