Re: [PATCH v2 2/2] drm/panel: Add driver for Novatek NT36523

From: Konrad Dybcio <konrad.dybcio@linaro.org>
To: Jianhua Lu <lujianhua000@gmail.com>,
	Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Sam Ravnborg <sam@ravnborg.org>, David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>, Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	~postmarketos/upstreaming@lists.sr.ht,
	phone-devel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] drm/panel: Add driver for Novatek NT36523
Date: Wed, 8 Mar 2023 12:04:19 +0100	[thread overview]
Message-ID: <dff4732c-df1f-0df8-b414-b039ab34c54b@linaro.org> (raw)
In-Reply-To: <ZAfasb9aKTgyjbFc@Gentoo>


On 8.03.2023 01:45, Jianhua Lu wrote:
> On Tue, Mar 07, 2023 at 11:34:55PM +0100, Linus Walleij wrote:
>> Hi Jianhua,
>>
>> thanks for your patch!
>>
>> It appears Konrad is working on a very similar driver, so I suggest merging
>> them into one Novatek NT36523 driver.
>>
>> Possibly we can fix this up first and then add Konrads Lenovo-panel with
>> a patch on top.
>>
>> On Mon, Feb 20, 2023 at 1:13 PM Jianhua Lu <lujianhua000@gmail.com> wrote:
>>
>>> Add a driver for panels using the Novatek NT36523 display driver IC.
>>>
>>> Signed-off-by: Jianhua Lu <lujianhua000@gmail.com>
>>
>> (...)
>>
>> I like how you abstract the panel with init commands in the panel info.
>>
>>> +enum dsi_cmd_type {
>>> +       INIT_DCS_CMD,
>>> +       DELAY_CMD,
>>> +};
>>> +
>>> +struct panel_init_cmd {
>>> +       enum dsi_cmd_type type;
>>> +       size_t len;
>>> +       const char *data;
>>> +};
>>> +
>>> +#define _INIT_DCS_CMD(...) { \
>>> +       .type = INIT_DCS_CMD, \
>>> +       .len = sizeof((char[]){__VA_ARGS__}), \
>>> +       .data = (char[]){__VA_ARGS__} }
>>> +
>>> +#define _INIT_DELAY_CMD(...) { \
>>> +       .type = DELAY_CMD,\
>>> +       .len = sizeof((char[]){__VA_ARGS__}), \
>>> +       .data = (char[]){__VA_ARGS__} }
>>
>> I have seen this type of reinvented wheels a few times now. Don't do this.
>>
>> Look into other recently merged drivers and look how they do it, for example
>> drivers/gpu/drm/panel/panel-himax-hx8394.c
>>
>> For example:
>>
>> - Use mipi_dsi_dcs_write_seq()
>>
>> - If the delay is just used at one point in the sequence, do not invent
>>   a command language like above for it, open code the delay instead
>>
>> - Try to decode as much magic as possible, if you look in Konrads
>>   driver you clearly see some standard MIPI commands, I bet you have
>>   some too.
>>
>> - Maybe use callbacks to send sequences instead of tables, like in
>>   the himax driver?
> Maybe I should create a wrapper of mipi_dsi_dcs_write_seq() for sync dual dsi mode.
Yes please, it'll come in useful.

Konrad
>>
>> Other than that it seems like something that could also handle the Lenovo
>> display, or the other way around, I don't know which driver is the best
>> starting point, but this one has the right Novatek name at least.
>>
>> Yours,
>> Linus Walleij