linux-kernel - Re: [PATCH] usb: typec: nb7vpq904m: add CONFIG

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Message-Id: <f28f78fc-84ce-4990-9126-4075f3d88e01@app.fastmail.com>
Date:   Thu, 22 Jun 2023 13:24:30 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Neil Armstrong" <neil.armstrong@...aro.org>,
        "Arnd Bergmann" <arnd@...nel.org>,
        "Heikki Krogerus" <heikki.krogerus@...ux.intel.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>
Cc:     "Bjorn Andersson" <andersson@...nel.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: nb7vpq904m: add CONFIG_DRM dependency

On Thu, Jun 22, 2023, at 12:39, Neil Armstrong wrote:
> Hi,
>
> On 22/06/2023 12:18, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@...db.de>
>> 
>> This driver calls directly into DRM functions and fails to link if
>> that is disabled:
>> 
>> ld.lld: error: undefined symbol: devm_drm_bridge_add
>> ld.lld: error: undefined symbol: devm_drm_of_get_bridge
>>>>> referenced by nb7vpq904m.c
>>>>>                drivers/usb/typec/mux/nb7vpq904m.o:(nb7vpq904m_probe) in archive vmlinux.a
>> 
>> Fixes: 88d8f3ac9c67e ("usb: typec: add support for the nb7vpq904m Type-C Linear Redriver")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> ---
>>   drivers/usb/typec/mux/Kconfig | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/usb/typec/mux/Kconfig b/drivers/usb/typec/mux/Kconfig
>> index 8c4d6b8fb75c3..f53ae24b6c048 100644
>> --- a/drivers/usb/typec/mux/Kconfig
>> +++ b/drivers/usb/typec/mux/Kconfig
>> @@ -37,7 +37,7 @@ config TYPEC_MUX_INTEL_PMC
>>   
>>   config TYPEC_MUX_NB7VPQ904M
>>   	tristate "On Semiconductor NB7VPQ904M Type-C redriver driver"
>> -	depends on I2C
>> +	depends on I2C && DRM
>>   	select REGMAP_I2C
>>   	help
>>   	  Say Y or M if your system has a On Semiconductor NB7VPQ904M Type-C
>
> I think it could be :
>
> +	depends on DRM || DRM=n
> +	select DRM_PANEL_BRIDGE if DRM

As far as I can tell, this would only avoid the link error
against devm_drm_of_get_bridge(), but not the one against
devm_drm_bridge_add(), which is defined in drm.ko through
drivers/gpu/drm/drm_bridge.c.

    Arnd