linux-kernel - Re: [PATCH 2/2] usb: typec: qcom-pmic-typec: register drm

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Message-ID: <d66c8268-24ee-e548-7a40-02f827c7c403@linaro.org>
Date:   Sun, 9 Jul 2023 23:11:46 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] usb: typec: qcom-pmic-typec: register drm_bridge

On 09/07/2023 14:25, Bryan O'Donoghue wrote:
> On 09/07/2023 04:48, Dmitry Baryshkov wrote:
>> The current approach to handling DP on bridge-enabled platforms requires
>> a chain of DP bridges up to the USB-C connector. Register a last DRM
>> bridge for such chain.
>>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>>   drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c | 25 +++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> diff --git a/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c 
>> b/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
>> index a905160dd860..ca832a28176e 100644
>> --- a/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
>> +++ b/drivers/usb/typec/tcpm/qcom/qcom_pmic_typec.c
>> @@ -17,6 +17,9 @@
>>   #include <linux/usb/role.h>
>>   #include <linux/usb/tcpm.h>
>>   #include <linux/usb/typec_mux.h>
>> +
>> +#include <drm/drm_bridge.h>
>> +
>>   #include "qcom_pmic_typec_pdphy.h"
>>   #include "qcom_pmic_typec_port.h"
>> @@ -33,6 +36,7 @@ struct pmic_typec {
>>       struct pmic_typec_port    *pmic_typec_port;
>>       bool            vbus_enabled;
>>       struct mutex        lock;        /* VBUS state serialization */
>> +    struct drm_bridge    bridge;
>>   };
>>   #define tcpc_to_tcpm(_tcpc_) container_of(_tcpc_, struct pmic_typec, 
>> tcpc)
>> @@ -146,6 +150,16 @@ static int qcom_pmic_typec_init(struct tcpc_dev 
>> *tcpc)
>>       return 0;
>>   }
>> +static int qcom_pmic_typec_attach(struct drm_bridge *bridge,
>> +                     enum drm_bridge_attach_flags flags)
>> +{
>> +    return flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR ? 0 : -EINVAL;
>> +}
> 
> Should that be -ENODEV instead ?

No. This bridge doesn't implement older bridge API, where the bridge had 
to create drm_connector itself. This implementation requires 
DRM_BRIDGE_ATTACH_NO_CONNECTOR and it is invalid to call it without this 
flag. Other bridges which have been converted to 
DRM_BRIDGE_ATTACH_NO_CONNECTOR implement the same semantics.

> 
>> +
>> +static const struct drm_bridge_funcs qcom_pmic_typec_bridge_funcs = {
>> +    .attach = qcom_pmic_typec_attach,
>> +};
>> +
>>   static int qcom_pmic_typec_probe(struct platform_device *pdev)
>>   {
>>       struct pmic_typec *tcpm;
>> @@ -208,6 +222,17 @@ static int qcom_pmic_typec_probe(struct 
>> platform_device *pdev)
>>       mutex_init(&tcpm->lock);
>>       platform_set_drvdata(pdev, tcpm);
>> +    tcpm->bridge.funcs = &qcom_pmic_typec_bridge_funcs;
>> +#if CONFIG_OF
>> +    tcpm->bridge.of_node = of_get_child_by_name(dev->of_node, 
>> "connector");
>> +#endif
>> +    tcpm->bridge.ops = DRM_BRIDGE_OP_HPD;
>> +    tcpm->bridge.type = DRM_MODE_CONNECTOR_USB;
>> +
>> +    ret = devm_drm_bridge_add(dev, &tcpm->bridge);
> 
> I think you need to either
> 
> Kconfig + depends on DRM
> 
> or
> 
> #if CONFIG_DRM

I guess I'm too used to always having DRM. This will need both Kconfig 
and source code parts. Will fix it in v2.

> 
> https://www.spinics.net/lists/kernel/msg4773470.html
> 
> Kconfig for preference
> 
> ---
> bod

-- 
With best wishes
Dmitry