[RFC PATCH] drm/panel: simple: panel-dpi: use bus-format to set bpc and bus_format

[Marek Vasut]

On 2/23/22 14:47, Maxime Ripard wrote:
> On Wed, Feb 23, 2022 at 02:45:30PM +0100, Marek Vasut wrote:
>> On 2/23/22 14:41, Maxime Ripard wrote:
>>> Hi,
>>>
>>> On Tue, Feb 22, 2022 at 09:47:23AM +0100, Max Krummenacher wrote:
>>>> Use the new property bus-format to set the enum bus_format and bpc.
>>>> Completes: commit 4a1d0dbc8332 ("drm/panel: simple: add panel-dpi support")
>>>>
>>>> Signed-off-by: Max Krummenacher <max.krummenacher at toradex.com>
>>>>
>>>> ---
>>>>
>>>>    drivers/gpu/drm/panel/panel-simple.c | 32 ++++++++++++++++++++++++++++
>>>>    1 file changed, 32 insertions(+)
>>>>
>>>> Relates to the discussion: https://lore.kernel.org/all/20220201110717.3585-1-cniedermaier@dh-electronics.com/
>>>>
>>>> Max
>>>>
>>>> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
>>>> index c5f133667a2d..5c07260de71c 100644
>>>> --- a/drivers/gpu/drm/panel/panel-simple.c
>>>> +++ b/drivers/gpu/drm/panel/panel-simple.c
>>>> @@ -453,6 +453,7 @@ static int panel_dpi_probe(struct device *dev,
>>>>    	struct panel_desc *desc;
>>>>    	unsigned int bus_flags;
>>>>    	struct videomode vm;
>>>> +	const char *format = "";
>>>>    	int ret;
>>>>    	np = dev->of_node;
>>>> @@ -477,6 +478,37 @@ static int panel_dpi_probe(struct device *dev,
>>>>    	of_property_read_u32(np, "width-mm", &desc->size.width);
>>>>    	of_property_read_u32(np, "height-mm", &desc->size.height);
>>>> +	of_property_read_string(np, "bus-format", &format);
>>>> +	if (!strcmp(format, "BGR888_1X24")) {
>>>> +		desc->bpc = 8;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_BGR888_1X24;
>>>> +	} else if (!strcmp(format, "GBR888_1X24")) {
>>>> +		desc->bpc = 8;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_GBR888_1X24;
>>>> +	} else if (!strcmp(format, "RBG888_1X24")) {
>>>> +		desc->bpc = 8;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RBG888_1X24;
>>>> +	} else if (!strcmp(format, "RGB444_1X12")) {
>>>> +		desc->bpc = 6;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RGB444_1X12;
>>>> +	} else if (!strcmp(format, "RGB565_1X16")) {
>>>> +		desc->bpc = 6;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RGB565_1X16;
>>>> +	} else if (!strcmp(format, "RGB666_1X18")) {
>>>> +		desc->bpc = 6;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RGB666_1X18;
>>>> +	} else if (!strcmp(format, "RGB666_1X24_CPADHI")) {
>>>> +		desc->bpc = 6;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RGB666_1X24_CPADHI;
>>>> +	} else if (!strcmp(format, "RGB888_1X24")) {
>>>> +		desc->bpc = 8;
>>>> +		desc->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
>>>> +	} else {
>>>> +		dev_err(dev, "%pOF: missing or unknown bus-format property\n",
>>>> +			np);
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>
>>> It doesn't seem right, really. We can't the bus format / bpc be inferred
>>> from the compatible? I'd expect two panels that don't have the same bus
>>> format to not be claimed as compatible.
>>
>> Which compatible ?
>>
>> Note that this is for panel-dpi compatible, i.e. the panel which has timings
>> specified in DT (and needs bus format specified there too).
> 
> panel-dpi is supposed to have two compatibles, the panel-specific one
> and panel-dpi. This would obviously be tied to the panel-specific one.

This whole discussion is about the one which only has 'panel-dpi' 
compatible and describes the panel in DT completely. The specific 
compatible is not present in DT when this patch is needed.